CA1084599A - Detection and maintenance of oscillations - Google Patents
Detection and maintenance of oscillationsInfo
- Publication number
- CA1084599A CA1084599A CA270,475A CA270475A CA1084599A CA 1084599 A CA1084599 A CA 1084599A CA 270475 A CA270475 A CA 270475A CA 1084599 A CA1084599 A CA 1084599A
- Authority
- CA
- Canada
- Prior art keywords
- oscillating system
- energy
- oscillating
- oscillation
- transmitter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000010355 oscillation Effects 0.000 title claims abstract description 47
- 238000012423 maintenance Methods 0.000 title claims description 3
- 238000001514 detection method Methods 0.000 title 1
- 238000000034 method Methods 0.000 claims abstract description 36
- 238000005259 measurement Methods 0.000 claims description 16
- 238000005452 bending Methods 0.000 claims 1
- 230000001702 transmitter Effects 0.000 claims 1
- 230000008859 change Effects 0.000 abstract description 19
- 230000006870 function Effects 0.000 description 12
- 238000010276 construction Methods 0.000 description 7
- 238000012545 processing Methods 0.000 description 7
- 230000005540 biological transmission Effects 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000009471 action Effects 0.000 description 4
- 230000008878 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 3
- 238000010420 art technique Methods 0.000 description 2
- 238000013016 damping Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000008054 signal transmission Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000010358 mechanical oscillation Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
- G08C19/00—Electric signal transmission systems
- G08C19/12—Electric signal transmission systems in which the signal transmitted is frequency or phase of ac
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
- G01B17/04—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring the deformation in a solid, e.g. by vibrating string
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/243—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the phase or frequency of ac
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/10—Measuring force or stress, in general by measuring variations of frequency of stressed vibrating elements, e.g. of stressed strings
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
- H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
Abstract
ABSTRACT
A method and apparatus for sensing the oscillating state of an oscillating system in a transmitter and for delivering energy to the oscillating system for maintaining the oscillation in the oscillating system. In order to measure a function, such as pressure or change of length, at least one frequency determinative parameter in the oscillating system is designed to be reacted upon by the selected function and a signal representative of the change in frequency is sensed and measured.
The sensing of the oscillations is effected along the same signal path as that used to deliver the necessary energy to maintain the oscillation in the system. The oscillating system may be either mechanical or electrical.
A method and apparatus for sensing the oscillating state of an oscillating system in a transmitter and for delivering energy to the oscillating system for maintaining the oscillation in the oscillating system. In order to measure a function, such as pressure or change of length, at least one frequency determinative parameter in the oscillating system is designed to be reacted upon by the selected function and a signal representative of the change in frequency is sensed and measured.
The sensing of the oscillations is effected along the same signal path as that used to deliver the necessary energy to maintain the oscillation in the system. The oscillating system may be either mechanical or electrical.
Description
.` ` 108459g Transmitters of various forms and constructions are used for converting a primary chemical or physical measurement function to a signal more adapted for transmission and additional processing than the primary measurement. In general, this conversion takes place such that the primary measurement function is appropriately converted into another physical or chemical measurement which either is the desired signal or, in known matter, can in a simple way be converted into desired signal form. In some cases the primary measurement can be directly converted into the desired signal form, for instance a change of length can be converted directly, by means of potentiometer, to a resistance change, while in many cases the conver-sion into the final form takes place via a secondary measurement. For example, a force or a liquid pressure is transformed to a change of length by allowing the primary function to influence an elastic body, the elonga-tion of which is measured with appropriate means, for instance strain -~ gauges.
Up to now, the components and equipment built thereof most adapted for signal processing and presentation have, from both a technical and economic point of view, been of analog nature, which ensures that most transmitters have been constructed for emitting an analog signal, i.e. the information from the transmitter has been emitted in the form of a level change of the output signal from the transmitter, for instance direct current change, a change of alternating current amplitude or a change of pressure, for instance air pressure.
The developments in recent years in the field of digital signal-processing techniques and the accompanying increase of achievable accuracy and stability has resulted in a requirement for conversion from analog to digital form to be inserted in the signal transmission chain from transmitter to signal processing equipment.
Other types of transmitters, which are better adapted for a ..
B~ 1 . :: ' : , - , :
-. , - ~ ,~ , ,, more direct connection to digital signal processing systems, are those emitting their information in the form of a frequency change instead of an amplitude change of the output signal. A signal transmission by frequency-modulation, in contrast to the amplitude-modulation of the analog transmitters, has, in addition to the extremely simple method of connection to the digital signal processing equipment, other advantages such as less interference sensitivity and lower demands upon the signal linQs.
Transmitters emitting information as a frequency modulated signal are of course built up such that the primary measurement, possibly after conversion in an appropriate conversion element, can effect the parameters in an electrically, acoustically or mechanically oscillating system (oscillating circuit), so that the inherent oscillation frequency of the oscillating system receives a change which is a function of the change of the primary measurement. Thus, for instance, the inherent oscillation frequency in an electrically oscillating system can be influenced by allowing the primary measurement to affect either the inductance or the capacitance or both simultaneously. In a mechanically oscillating system the mass or its return force, i.e. the spring constant, can in a corresponding manner be influenced by the primary or secondary measurement and thereby give rise to a frequency change which can be measured with known methods.
Owing to the fact that the oscillating systems capable of being used in practice always have losses, in the form of electrical resistance losses or mechanical friction losses, energy must be delivered to the oscil-lating system in order to be able to maintain the oscillation for a longer period of time. This additional energy is obtained in such a manner that the oscillation is measured by appropriate methods, is amplified and then is returned to the oscillating system in such a phase, that the oscillation receives an energy addition. An example of this long known technique is
Up to now, the components and equipment built thereof most adapted for signal processing and presentation have, from both a technical and economic point of view, been of analog nature, which ensures that most transmitters have been constructed for emitting an analog signal, i.e. the information from the transmitter has been emitted in the form of a level change of the output signal from the transmitter, for instance direct current change, a change of alternating current amplitude or a change of pressure, for instance air pressure.
The developments in recent years in the field of digital signal-processing techniques and the accompanying increase of achievable accuracy and stability has resulted in a requirement for conversion from analog to digital form to be inserted in the signal transmission chain from transmitter to signal processing equipment.
Other types of transmitters, which are better adapted for a ..
B~ 1 . :: ' : , - , :
-. , - ~ ,~ , ,, more direct connection to digital signal processing systems, are those emitting their information in the form of a frequency change instead of an amplitude change of the output signal. A signal transmission by frequency-modulation, in contrast to the amplitude-modulation of the analog transmitters, has, in addition to the extremely simple method of connection to the digital signal processing equipment, other advantages such as less interference sensitivity and lower demands upon the signal linQs.
Transmitters emitting information as a frequency modulated signal are of course built up such that the primary measurement, possibly after conversion in an appropriate conversion element, can effect the parameters in an electrically, acoustically or mechanically oscillating system (oscillating circuit), so that the inherent oscillation frequency of the oscillating system receives a change which is a function of the change of the primary measurement. Thus, for instance, the inherent oscillation frequency in an electrically oscillating system can be influenced by allowing the primary measurement to affect either the inductance or the capacitance or both simultaneously. In a mechanically oscillating system the mass or its return force, i.e. the spring constant, can in a corresponding manner be influenced by the primary or secondary measurement and thereby give rise to a frequency change which can be measured with known methods.
Owing to the fact that the oscillating systems capable of being used in practice always have losses, in the form of electrical resistance losses or mechanical friction losses, energy must be delivered to the oscil-lating system in order to be able to maintain the oscillation for a longer period of time. This additional energy is obtained in such a manner that the oscillation is measured by appropriate methods, is amplified and then is returned to the oscillating system in such a phase, that the oscillation receives an energy addition. An example of this long known technique is
- 2 --, .
- : :
1~84S99 the various oscillator couplings which are found in the field of radio techniques. A corresponding method is utilized when using mechanically oscillating systems, for instance tuning fork oscillators or transmitters based on a change in the frequency of an oscillating string. In these constructions the mechanically oscillating system is excited with appropri-ate means, for instance an electromagnet, and the motion or velocity of the oscillating system is measured with another element adapted to do this, for instance a permanent magnet coil. Owing to the mechanical oscillation a voltage is generated in the permanent magnet coil, which voltage after amplification is conducted to the excitation coil, thereby maintaining the voltage continuously. Even though these methods for maintaining a continuous oscillation have been proved to be satisfactory for many applications, they have several disadvantages, particularly for use in transmitters.
The known methods, described above, for maintaining a continuous oscillation in an oæcillating system require that, besides the very oscillating system, another construction element be included in order to be able to measure the oscillation state of the oscillating system, so that energy can be fed back to the oscillating system and compensation of the circuit losses can take place. The insertion of such a sensing element complicates the construction and also increases the cost of the construction.
Moreover, the construction cannot be formed in the most efficient way for accuracy and stability.
Furthermore, the known methods also require that two signal paths exist, one for the delivery of the necessary energy addition to the oscillating system and the other for sensing the oscillation state of the oscillating system. This means a technical complication as well as an economic loading for the construction. The technical complication is related to the fact that both signal paths must be well separated so that _ 3 _ : . : . - : . . . : .
. . . ~ , : .
.
1~)84599 energy transmission cannot occur. Should the paths not be well separated, an oscillation can arise, the frequency of which is not a function of the parameters of the oscillating system. From an economic point of view the required doubling of the signal paths means, that the number of wires in an electrical system increases and also that the wires must be separated from each other in the best possible way. Such disadvantages are, of course, particularly valid for transmitters which operate in difficult surroundings and hence require special configuration of the signal lines.
The above mentioned disadvantages involved in the prior art techniques have proven to have such a great practical importance, that they have overshadowed the above mentioned advantages of having a frequency-modulated signal and have prevented the development, to be desired per se, of transmitters having a frequency-modulated output signal.
By a method and an apparatus according to the invention the above mentioned disadvantages in the prior art techniques have been over-come.
Thus, the present invention relates to a method for sensing the oscillation state of an oscillating system in a transmitter and for delivering energy to the oscillating system for maintaining the oscillation in the oscillating system, wherein at least one frequency-determinative parameter in the oscillating system is affected by a measurement, and the method according to the invention is in its broadest aspect characterized in that the sensing of the oscillation state of the oscillating system takes place by means of the same signal path as the delivery of the energy for the maintenance of the oscillationin the oscillating system.
In a method according to the invention the energy can preferably be delivered to the oscillating system during a time period which is shorter than the time interval between the end of one energy delivery and the begin-ning of the next. Moreover, the energy can preferably be delivered during .
~ -- ~ :
.
'``'` 1~8459g a time period which is not longer than a whole period of the oscillation in the oscillating system. In an often preferred method according to the invention the energy is delivered in pulses, the duration of which is essentially shorter than a half period of the oscillation in the oscillating system.
As mentioned above, the present invention also relates to an apparatus for carrying out the method.
A method and an apparatus according to the invention can be used for mechanically, electrically or acoustically oscillating systems or combinations of these. It has been proven that mechanically oscillating systems can, in transmitters having a frequency-modulated output signal, offer certain advantages over, for instance, electrically oscillating systems.
In the following description with reference to the accompanying drawings, however, not only methods and apparatus using mechanically oscillating systems are described but also methods and apparatus using electrically oscillating systems.
Figure 1 is a schematic view of an embodiment of an apparatus according to the invention, by means of which the method according to the invention can be carried out using a mechanically oscillating system;
Figure 2 is a schematic view of an embodiment using an electrically osclllating system;
Figures 3 and 4 are schematic views of further embodiments using a mechanically oscillating system;
Generally, a method according to the invention implies that sensing of the oscillation state in an oscillating system of a transmitter , . ~ . . : , . , ', ~: .
: ' ' ~' " ' 1084S9~
takes place by means of the same signal path as delivery of energy to the oscillating system for maintaining the oscillation in the oscillating system.
In an apparatus shown in Figure 1 for carrying out such a method, a transmitter 1 includes a mechanically oscillating system which in this case is represented by an oscillating band 2. The band, which is shown to be curved is mounted between two points of mounting, and can for instance be an oscillating band as disclosed in Swedish Patent No. 332,902.
The transmitter 1 further includes means for sensing the state of the oscillating system and for feeding energy into the oscillating system, in this case a coil 3. The coil 3 is positioned near to the band and is formed such that a current pulse through the coil affects the band with a force pulse simultaneously as a motion in the band generates a voltage over the coil. The transmitter is furthermore constructed such that the function being measured influences the mechanically oscillating system, i.e. the band 2, so that its inherent oscillation frequency is changed as a result of a change of the function. A transmitter can be directly connected to a measuring ob~ect or via a converting element (secondary measuring ob~ect), for instance as disclosed in the Swedish Patent No. 398,268. The energy delivery to the bancl 2 as well as the sensing of the motion of the band can of course take place with other means than the coil 3, for instance piezo-electric, pneumatic or acoustic means. The transmitter 1 is connected via a signal line 4 to a device constructed for sensing the oscillation state of the oscillating system 2 and for delivering an energy pulse to the oscillat-ing system at appropriate points of time. In the embodiment shown in Figure 1, the line 4 is a two-wire cable which in the transmitter 1 is connected to the coil 3 and at the other end is connected to a device for sensing the oscillation state, here represented by the amplifier 5, as well as to a pulse generator 6 which is constructed such that upon a signal ~o84s99 from its control input (trigger input) 7 it can give a current pul~e through the coil 3. The control input 7 of the pulse generator is connected to the output of the device 5 via a control circuit 8. The mode of operation of the coupling shown in Figure 1 is as follows: supposing that at the beginning the oscillating system, i.e. in this embodiment the band 2, is in a state of re-pose. A start signal is delivered to the control circuit 8 via a start signal wire 9. The controlcircuit 8 generates a signal in the control input 7 of the pulse generator 6, so that the pulse generator delivers an energy pulse to the oscillating system, i.e. in this case a current pulse through the coil 3. The input of the part of the equipment sensing the oscillation state, i.e. in this case the amplifier 5, can, should it be necessary, be protected by instantane-ously disconnecting the input from the signal line from the transmitter or by taking other protection steps, for instance switches or contactor diodes. As a result of the energy pulse from the pulse generator 6, the oscillating system 2 will be imparted with a more or less damped oscillation state. The frequency of this oscillation will be dependent on the configuration of the oscillating system and magnitude of the function which affects the frequency-determining parameter or parameters. The oscillation state of the oscillating system 2 and thus its frequency is sensed as a voltage over the connections of the coil 3 by means adapted for this (in this embodiment the amplifier 5) to the output of which frequency determina-tion (classification) means can, in conventional manner, be connected (not shown). The chief object of the control circuit 8 is to deliver a control signal to the pulse generator 6, so that a new energy pulse can be delivered to the oscillating system at such point of time that this energy delivery does not to any essential extent influence the oscillating state of the oscillating system in any respect other than an increase of the amplitude of the oscillation. Thus, the control circuit 8 can include means for, for instance, determination of the zero intersection of the oscillation, ' ' . . - ~ , ~:
,: '' ~0~4599 means for the determination of the point of time when the amplitude of the damped oscillation becomes lower than a determined limit value and/or means for determining the time that has passed from preceding energy pulse or the number of oscillation~ the oscillating system has been made since preceding energy pulse delivery, as well as means for controlling the energy contents of the energy pulse delivered from the pulse generator 6.
The control circuit 8 can furthermore include means for phase distortion of the incoming signals in order to ensure that the energy pulse is delivered in the right moment. Such phase distortion means can of course also be embodied in the amplifier 5, which also can include filters for filtering out interference signals, which are outside the range of frequencies within which the oscillating frequency of the oscillating system may vary as a result of variations of the primary measurement function. In the example stated above it has been assumed that the primary measurement function affects the frequency determining parameter or parameters of the oscillating system and that consequently the transmitter information is transmitted as a frequency change. The method according to the invention can, of course, also be used in cases when the primary measurement lnfluences the damping conditions of the oscillating system. In these cases means are arranged in the equipment, for instance in the control circuit 8, for determining the damping of the oscLllation in a manner known per se, for instance by determining the number of oscillations which the oscillating system must perform in order to achieve a predetermined percental decrease of the amplitude.
A method and an apparatus according to the invention is of course not limited only to be used in connection with mechanically oscillat-ing systems, but can advantageously be used also in cases when the transmitter has an electrically oscillating system (oscillating circuit), the frequency or damping-determining parameter or parameters of which being affected by 10l~59~
the primary measuring magnitude. Figure 2 shows a transmitter 10 which includes an electrically, parallel oscillating system (parallel oscilla-tion circuit) consisting of a capacitance 11 and an inductance 12 which, via a signal path 13 consisting of a wire pair 13a and 13b, is connected - to an input amplifier 14 and a pulse generator 15 in the same manner as stated above in the description of Figure 1. The conduits 13a and 13b are for practical reasons, positioned near to each other, because when using larger conduit lengths problems can be caused owing to the fact that the capacitance between the conduits will generate a capacitance parallel with 10 the capacitance 11 resulting in a change of the self-oscillation frequency of the oscillating system. This interferring influence can be decreased by surrounding one of the conduits, for instance the conduit 13a as shown, with a separate shield 16. This shield is given the same potential relative to the conduit 13b, as the conduit 13a has, by connecting the shield to the output of an amplifier 17, the input of which is connected to the conduits 13a and 13b. The amplifier 14 can, of course, be utilized for the same purpose. The apparatus shown in Figure 2 includes, in conformity with the apparatus shown in Figure 1, a control input, a control circuit and a start signal line. The mode of operation is the same as described above for the 20 apparatus according to Figure 1.
Another embodiment of an apparatus for carrying out the method according to the invention is shown in Figure 3. The transmitter in this embodiment is shown to have a mechanically oscillating system 22 in a similar way as the embodiment shown in Figure 1. However, the apparatus can, of course, have an electrically oscillating system, for instance a system as described above with reference to Figure 2. A coil 23 is used as a means for delivering energy to the oscillating system 22 and for sensing its oscillating motion. The coil 23 is connected to a device for sensing the oscillations and for delivering the energy pulses via a signal path 24 ~,
- : :
1~84S99 the various oscillator couplings which are found in the field of radio techniques. A corresponding method is utilized when using mechanically oscillating systems, for instance tuning fork oscillators or transmitters based on a change in the frequency of an oscillating string. In these constructions the mechanically oscillating system is excited with appropri-ate means, for instance an electromagnet, and the motion or velocity of the oscillating system is measured with another element adapted to do this, for instance a permanent magnet coil. Owing to the mechanical oscillation a voltage is generated in the permanent magnet coil, which voltage after amplification is conducted to the excitation coil, thereby maintaining the voltage continuously. Even though these methods for maintaining a continuous oscillation have been proved to be satisfactory for many applications, they have several disadvantages, particularly for use in transmitters.
The known methods, described above, for maintaining a continuous oscillation in an oæcillating system require that, besides the very oscillating system, another construction element be included in order to be able to measure the oscillation state of the oscillating system, so that energy can be fed back to the oscillating system and compensation of the circuit losses can take place. The insertion of such a sensing element complicates the construction and also increases the cost of the construction.
Moreover, the construction cannot be formed in the most efficient way for accuracy and stability.
Furthermore, the known methods also require that two signal paths exist, one for the delivery of the necessary energy addition to the oscillating system and the other for sensing the oscillation state of the oscillating system. This means a technical complication as well as an economic loading for the construction. The technical complication is related to the fact that both signal paths must be well separated so that _ 3 _ : . : . - : . . . : .
. . . ~ , : .
.
1~)84599 energy transmission cannot occur. Should the paths not be well separated, an oscillation can arise, the frequency of which is not a function of the parameters of the oscillating system. From an economic point of view the required doubling of the signal paths means, that the number of wires in an electrical system increases and also that the wires must be separated from each other in the best possible way. Such disadvantages are, of course, particularly valid for transmitters which operate in difficult surroundings and hence require special configuration of the signal lines.
The above mentioned disadvantages involved in the prior art techniques have proven to have such a great practical importance, that they have overshadowed the above mentioned advantages of having a frequency-modulated signal and have prevented the development, to be desired per se, of transmitters having a frequency-modulated output signal.
By a method and an apparatus according to the invention the above mentioned disadvantages in the prior art techniques have been over-come.
Thus, the present invention relates to a method for sensing the oscillation state of an oscillating system in a transmitter and for delivering energy to the oscillating system for maintaining the oscillation in the oscillating system, wherein at least one frequency-determinative parameter in the oscillating system is affected by a measurement, and the method according to the invention is in its broadest aspect characterized in that the sensing of the oscillation state of the oscillating system takes place by means of the same signal path as the delivery of the energy for the maintenance of the oscillationin the oscillating system.
In a method according to the invention the energy can preferably be delivered to the oscillating system during a time period which is shorter than the time interval between the end of one energy delivery and the begin-ning of the next. Moreover, the energy can preferably be delivered during .
~ -- ~ :
.
'``'` 1~8459g a time period which is not longer than a whole period of the oscillation in the oscillating system. In an often preferred method according to the invention the energy is delivered in pulses, the duration of which is essentially shorter than a half period of the oscillation in the oscillating system.
As mentioned above, the present invention also relates to an apparatus for carrying out the method.
A method and an apparatus according to the invention can be used for mechanically, electrically or acoustically oscillating systems or combinations of these. It has been proven that mechanically oscillating systems can, in transmitters having a frequency-modulated output signal, offer certain advantages over, for instance, electrically oscillating systems.
In the following description with reference to the accompanying drawings, however, not only methods and apparatus using mechanically oscillating systems are described but also methods and apparatus using electrically oscillating systems.
Figure 1 is a schematic view of an embodiment of an apparatus according to the invention, by means of which the method according to the invention can be carried out using a mechanically oscillating system;
Figure 2 is a schematic view of an embodiment using an electrically osclllating system;
Figures 3 and 4 are schematic views of further embodiments using a mechanically oscillating system;
Generally, a method according to the invention implies that sensing of the oscillation state in an oscillating system of a transmitter , . ~ . . : , . , ', ~: .
: ' ' ~' " ' 1084S9~
takes place by means of the same signal path as delivery of energy to the oscillating system for maintaining the oscillation in the oscillating system.
In an apparatus shown in Figure 1 for carrying out such a method, a transmitter 1 includes a mechanically oscillating system which in this case is represented by an oscillating band 2. The band, which is shown to be curved is mounted between two points of mounting, and can for instance be an oscillating band as disclosed in Swedish Patent No. 332,902.
The transmitter 1 further includes means for sensing the state of the oscillating system and for feeding energy into the oscillating system, in this case a coil 3. The coil 3 is positioned near to the band and is formed such that a current pulse through the coil affects the band with a force pulse simultaneously as a motion in the band generates a voltage over the coil. The transmitter is furthermore constructed such that the function being measured influences the mechanically oscillating system, i.e. the band 2, so that its inherent oscillation frequency is changed as a result of a change of the function. A transmitter can be directly connected to a measuring ob~ect or via a converting element (secondary measuring ob~ect), for instance as disclosed in the Swedish Patent No. 398,268. The energy delivery to the bancl 2 as well as the sensing of the motion of the band can of course take place with other means than the coil 3, for instance piezo-electric, pneumatic or acoustic means. The transmitter 1 is connected via a signal line 4 to a device constructed for sensing the oscillation state of the oscillating system 2 and for delivering an energy pulse to the oscillat-ing system at appropriate points of time. In the embodiment shown in Figure 1, the line 4 is a two-wire cable which in the transmitter 1 is connected to the coil 3 and at the other end is connected to a device for sensing the oscillation state, here represented by the amplifier 5, as well as to a pulse generator 6 which is constructed such that upon a signal ~o84s99 from its control input (trigger input) 7 it can give a current pul~e through the coil 3. The control input 7 of the pulse generator is connected to the output of the device 5 via a control circuit 8. The mode of operation of the coupling shown in Figure 1 is as follows: supposing that at the beginning the oscillating system, i.e. in this embodiment the band 2, is in a state of re-pose. A start signal is delivered to the control circuit 8 via a start signal wire 9. The controlcircuit 8 generates a signal in the control input 7 of the pulse generator 6, so that the pulse generator delivers an energy pulse to the oscillating system, i.e. in this case a current pulse through the coil 3. The input of the part of the equipment sensing the oscillation state, i.e. in this case the amplifier 5, can, should it be necessary, be protected by instantane-ously disconnecting the input from the signal line from the transmitter or by taking other protection steps, for instance switches or contactor diodes. As a result of the energy pulse from the pulse generator 6, the oscillating system 2 will be imparted with a more or less damped oscillation state. The frequency of this oscillation will be dependent on the configuration of the oscillating system and magnitude of the function which affects the frequency-determining parameter or parameters. The oscillation state of the oscillating system 2 and thus its frequency is sensed as a voltage over the connections of the coil 3 by means adapted for this (in this embodiment the amplifier 5) to the output of which frequency determina-tion (classification) means can, in conventional manner, be connected (not shown). The chief object of the control circuit 8 is to deliver a control signal to the pulse generator 6, so that a new energy pulse can be delivered to the oscillating system at such point of time that this energy delivery does not to any essential extent influence the oscillating state of the oscillating system in any respect other than an increase of the amplitude of the oscillation. Thus, the control circuit 8 can include means for, for instance, determination of the zero intersection of the oscillation, ' ' . . - ~ , ~:
,: '' ~0~4599 means for the determination of the point of time when the amplitude of the damped oscillation becomes lower than a determined limit value and/or means for determining the time that has passed from preceding energy pulse or the number of oscillation~ the oscillating system has been made since preceding energy pulse delivery, as well as means for controlling the energy contents of the energy pulse delivered from the pulse generator 6.
The control circuit 8 can furthermore include means for phase distortion of the incoming signals in order to ensure that the energy pulse is delivered in the right moment. Such phase distortion means can of course also be embodied in the amplifier 5, which also can include filters for filtering out interference signals, which are outside the range of frequencies within which the oscillating frequency of the oscillating system may vary as a result of variations of the primary measurement function. In the example stated above it has been assumed that the primary measurement function affects the frequency determining parameter or parameters of the oscillating system and that consequently the transmitter information is transmitted as a frequency change. The method according to the invention can, of course, also be used in cases when the primary measurement lnfluences the damping conditions of the oscillating system. In these cases means are arranged in the equipment, for instance in the control circuit 8, for determining the damping of the oscLllation in a manner known per se, for instance by determining the number of oscillations which the oscillating system must perform in order to achieve a predetermined percental decrease of the amplitude.
A method and an apparatus according to the invention is of course not limited only to be used in connection with mechanically oscillat-ing systems, but can advantageously be used also in cases when the transmitter has an electrically oscillating system (oscillating circuit), the frequency or damping-determining parameter or parameters of which being affected by 10l~59~
the primary measuring magnitude. Figure 2 shows a transmitter 10 which includes an electrically, parallel oscillating system (parallel oscilla-tion circuit) consisting of a capacitance 11 and an inductance 12 which, via a signal path 13 consisting of a wire pair 13a and 13b, is connected - to an input amplifier 14 and a pulse generator 15 in the same manner as stated above in the description of Figure 1. The conduits 13a and 13b are for practical reasons, positioned near to each other, because when using larger conduit lengths problems can be caused owing to the fact that the capacitance between the conduits will generate a capacitance parallel with 10 the capacitance 11 resulting in a change of the self-oscillation frequency of the oscillating system. This interferring influence can be decreased by surrounding one of the conduits, for instance the conduit 13a as shown, with a separate shield 16. This shield is given the same potential relative to the conduit 13b, as the conduit 13a has, by connecting the shield to the output of an amplifier 17, the input of which is connected to the conduits 13a and 13b. The amplifier 14 can, of course, be utilized for the same purpose. The apparatus shown in Figure 2 includes, in conformity with the apparatus shown in Figure 1, a control input, a control circuit and a start signal line. The mode of operation is the same as described above for the 20 apparatus according to Figure 1.
Another embodiment of an apparatus for carrying out the method according to the invention is shown in Figure 3. The transmitter in this embodiment is shown to have a mechanically oscillating system 22 in a similar way as the embodiment shown in Figure 1. However, the apparatus can, of course, have an electrically oscillating system, for instance a system as described above with reference to Figure 2. A coil 23 is used as a means for delivering energy to the oscillating system 22 and for sensing its oscillating motion. The coil 23 is connected to a device for sensing the oscillations and for delivering the energy pulses via a signal path 24 ~,
3 _ 9 _ : - .: ' :
: . . - ` . ..
'`' ~ , ,` : ' ~
. - . . . ` ` ' ` . .
consisting of a wire pair 24a and 24b. One of the wires, 24b as shown, is connected to a ground point 25 common for the apparatus. A pulse ; generator consisting of a condenser 26 and a thyristor, or a semi-conductor coupling 29 equivalent as to operation, are used for generating energy pulses. The condenser is charged to a voltage adjustable manually or electrically by a voltage unit 27 over a resistance 28. The thyristor or the semi-conductor coupling 29 can be brought into conducting state by a control pulse in a control wire 30, so that the condenser 26 is discharged through the coil 23 in the transmitter 21 and thereby delivers energy to the oscillating system 22. The coil 23 in the transmitter 21 is also connected to an amplifier 31, preferably as shown in Figure 3 via an electrically governed reversing switch 32 and a filter 33. The object of the switch 32 is to protect the amplifier input from the high-energy pulse upon the discharge of the condenser 26 through the thyristor 29. The ob~ect of the filter 33 is to decrease interference by frequencies outside of the frequency range within which the inherent frequency of the oscillating system may vary. A signal representing the damped inherent frequency of the oscillating system will be found at the output of the amplifier 31 between the points of time for the energy pulse delivery. This signal is conducted to one input of a comparing unit 34, the reference voltage of which is set either manually or with means known per se via conduit 35, and is controlled by the signal from amplifier 31. The output signal of the comparing unit, which signal is a frequncy corresponding to the frequency with which the oscillating system oscillates but having constant amplitude, is conducted to a counter 36. This counter is constructed such that, after counting a predetermined number of pulses, it emits a pulse to a circuit 37 (monostable flip-flop) arranged for delivering a control pulse, determined in time extension and amplitude, to the thyristor 29 and, inoccurring cases, to the switch 32, and thereby an energy pulse is delivered to the oscillating iO8D~59~
system in accordance with what has been described above. Immediately after the energy pulse has been delivered, the amplifier 31 is again switched in, via switch 32 and filter 33, at the same time as the counter 36 is reset, and the cycle is repeated. The frequency determined by the oscillating system 22 is taken out from the output of the amplifier 31 or the comparing ~ unit 34. The lower frequency delivered from the output of the counter 36 - can also be used as output signal. Means required for starting the apparatus (for instance a start signal line 9 as shown in Figure 1) as well as conventional means required for resetting the counter and governing the progress are not shown in Figure 3.
A further embodiment of an apparatus for carrying out the method according to the invention is shown in Figure 4. A transmitter, here designated with the reference numeral 41, is proposed to have a mechanically oscillating system, here designated 42. The oscillation state of the system can be sensed by a coil 43 which also is used for energy delivery to the oscillatlng system. The coil 43 is, as is the case in embodiments described above, connected to an oscillating sensing and energy pulse generating device by means of a signal path 44 consisting of a pair of wires 44a and 44b, and the wire 44b is connected to the ground point 45 common for the apparatus. The other wire 44a is connected to an amplifier 47, preferably via a breaker 46. The output from the amplifier 47 is connected to a so-called phase-locked circuit, consisting of a phase detector 48 and a voltage governed oscillator 49, as well as to a control circuit 50 which includes means and connections (not shown) for controlling the sequence of operations.
The phase detector 48 receives a signal from the amplifier 47 and also a reference signal from the output of the oscillator 49. The oscillator 49 receives its control voltage from the output of the phase detector 48 via a switch 51 and a memory 52. The output of the oscillator 49 can also be connected to the coil 43 via a switch 53 and the conduit 44a, preferably - , ., via a power amplifier (not shown). The mode of operation of the apparatus is as follows: Assume that the oscillating system is in a state of repose and in a state of equilibrium. A first energy pulse is impressed on the oscillating system by impressing a current pulse on the coil 43. This current pulse can be obtained either by a device described above in connec-tion to Figure 3 or by closing the switch 53 in the embodiment of Figure 4.
Immediately after the energy pulse is over, switch 53 opens and switches 46 and 51 close. The switch 54 is open. The mechanically oscillating system 42 generates in the coil 43 a voltage which, via the signal path 44, is conducted to the amplifier 47, and a signal representing the oscillation state of the system is obtained on the output of the amplifier. This signal is conducted to one of the inputs of the phase detector 48. The other input of the phase detector is energized from the output of the oscillator 49 which is constructed such that its frequency is lying near to the frequency of the oscillating system. The signal from the phase detector will represent the phase differences between the signals impressed on the two inputs and thereby also the frequency difference between these signals. This signal from the phase detector is conducted back to the osclllator 49 vla the switch 51 and the signal-following memory 52, so that the frequency of the oscillator changes in a direction equivalent to the frequency generated by the oscillating system. The memory 52 is assumed to contain means necessary for the stability of this control clrcuit, for instance filters. After ad~ustment of the frequency for the oscillator 49 this frequency will coincide with the frequency generated by the oscillating system 42 and, furthermore, will be lying in a determined phase relation relative to this latter frequency. After a certain time, determined by the control means included in the control circuit 50, for instance time circuits, counting circuits and circuits sensing the signal level or combinations of these circuits, a signal is delivered for generating an energy pulse to the .~
-~ 1084595~
oscillating system. At this point in time the switch 51 opens and the frequency of the oscillator 49 remains at a value lt had before the switch was opened. Immediately after this the switch 46 opens at the same time as switch 54 closes, thereby making it possible for the control circuit 50 to receive information about the signal from the oscillator 49. In an appro-priate state for the signal from the oscillator 49, the switch 53 receives a signal from the control circuit 50 and closes, and an energy pulse, the length of which is determined by the control circuit 50, is impressed on the oscillating system via the coil 43. Immediately after the termination of the energy pulse the switches 46 and 51 close and the switch 54 opens. By this apparatus, in which the phase-locked circuit is an essential part, a feeding of the energy pulse into the oscillating system is ensured in such a phase state, that interferences in the oscillation of the system are prevented. The frequency generated in the oscillating system will be ; reproduced on the output of the oscillator 49 as soon as the phase-locked circuit has locked. Thus, the frequency variations of the oscillator 49 is a measure of the primary measurement function affecting the oscillating system 42. The var:Lation in the measurement function can also be taken out as an analog signal from the output of the phase detector 48, preferably after appropriate low-pass filtering. Owing to the fact that the frequency of the oscillator 49 strictly follows the frequency of the oscillating system 42, except for the short time intervals when the energy pulse is imparted to the oscillating system, the variations of the measuring magnitude can also be followed between the energy pulses without interferencesoccurring on this signal upon energy pulse delivery. Since the phase-locked circuit also operates as a band pass filter, the signal from the oscillator 49 will be free from interferences and furthermore have a high level, which facilitates and simplifies further signal processing. The band width for the filter operation which the phase-locked circuit performs is dependent on the filters ~08~S99 (here assumed to be positioned in the memory 52) being engaged between the output of the phase detector 48 and the control input of the oscillator 49. These filter actions also determine the so-called capture range of the phase-locked circuit, i.e. the largest frequency difference that can exist between the frequency of the oscillator 49 upon the start of the system and the frequency generated by the oscillating system 42. In order to ensure a rapid and secure start of the system, the filter actions must consequently be formed such that this can occur. Such a filter configuration, however, means that the equivalent band width of the filter action of the phase-locked circuit will be comparatively large, which is a disadvantage for the suppression of possible interference signals. The filter action can therefore, according to known technique, be formed with the aid of electron-ically controlled filter elements which are governed via the output of the phase detector 48 and circuits in the control circuit 50 connected to the output in such a manner, that, as soon as the frequency of the oscillator 49 follows the frequency of the oscillating system 42, the parameters for the filter between the output of the phase detector 48 and the input of the oscillator 49 are changed in such a direction that the equivalent band width of the phase-locked circuit decreases.
Naturally, the above described method with references to Figures 3 and 4 can be combined with the method described in connection to Figure 2 for decreasing the influence of cable capacitance.
The energy pulse delivered to the oscillating system for maintain-ing its oscillation can be given various form and time extension. A pulse can be used which is of the same form as a multiple of a whole or a half period of the frequency of the oscillating system in order to avoid to the utmost possible extent a non-desired interference of the state of the oscillating system in other respects than the intended amplitude increase.
However, it is desirable, from a measuring technique point of view, to design ``;:` ' ~V84599 the transmitter and its oscillating systems such that a frequency change as large as possible is achievable. In such a case it may be appropriate to use an apparatus of the kind shown in Figure 4 in order to produce a pulse form being equal to a multiple of a whole or a half oscillating period.
In this case it has proved to be advantageous to use a pulse which is short in comparison with the oscillating period delivered to the oscillating system at appropriate points in its oscillating motion.
Within the frame of the present invention, although not shown, it is possible to use the same device for sensing the state of and for delivering energy to a plurality of transmitters by providing a switch between the transmitters and said device in a manner known per se. Moreover, the signal paths in the embodlments described above and shown in the drawings consist of electric wires. However, within the frame of the present invention the signal paths can consist of other transmission means than electric wires, as for instance microwave transmission, acoustic transmission, optical transmission.
.
:
- , : . ~ .
: . . - ` . ..
'`' ~ , ,` : ' ~
. - . . . ` ` ' ` . .
consisting of a wire pair 24a and 24b. One of the wires, 24b as shown, is connected to a ground point 25 common for the apparatus. A pulse ; generator consisting of a condenser 26 and a thyristor, or a semi-conductor coupling 29 equivalent as to operation, are used for generating energy pulses. The condenser is charged to a voltage adjustable manually or electrically by a voltage unit 27 over a resistance 28. The thyristor or the semi-conductor coupling 29 can be brought into conducting state by a control pulse in a control wire 30, so that the condenser 26 is discharged through the coil 23 in the transmitter 21 and thereby delivers energy to the oscillating system 22. The coil 23 in the transmitter 21 is also connected to an amplifier 31, preferably as shown in Figure 3 via an electrically governed reversing switch 32 and a filter 33. The object of the switch 32 is to protect the amplifier input from the high-energy pulse upon the discharge of the condenser 26 through the thyristor 29. The ob~ect of the filter 33 is to decrease interference by frequencies outside of the frequency range within which the inherent frequency of the oscillating system may vary. A signal representing the damped inherent frequency of the oscillating system will be found at the output of the amplifier 31 between the points of time for the energy pulse delivery. This signal is conducted to one input of a comparing unit 34, the reference voltage of which is set either manually or with means known per se via conduit 35, and is controlled by the signal from amplifier 31. The output signal of the comparing unit, which signal is a frequncy corresponding to the frequency with which the oscillating system oscillates but having constant amplitude, is conducted to a counter 36. This counter is constructed such that, after counting a predetermined number of pulses, it emits a pulse to a circuit 37 (monostable flip-flop) arranged for delivering a control pulse, determined in time extension and amplitude, to the thyristor 29 and, inoccurring cases, to the switch 32, and thereby an energy pulse is delivered to the oscillating iO8D~59~
system in accordance with what has been described above. Immediately after the energy pulse has been delivered, the amplifier 31 is again switched in, via switch 32 and filter 33, at the same time as the counter 36 is reset, and the cycle is repeated. The frequency determined by the oscillating system 22 is taken out from the output of the amplifier 31 or the comparing ~ unit 34. The lower frequency delivered from the output of the counter 36 - can also be used as output signal. Means required for starting the apparatus (for instance a start signal line 9 as shown in Figure 1) as well as conventional means required for resetting the counter and governing the progress are not shown in Figure 3.
A further embodiment of an apparatus for carrying out the method according to the invention is shown in Figure 4. A transmitter, here designated with the reference numeral 41, is proposed to have a mechanically oscillating system, here designated 42. The oscillation state of the system can be sensed by a coil 43 which also is used for energy delivery to the oscillatlng system. The coil 43 is, as is the case in embodiments described above, connected to an oscillating sensing and energy pulse generating device by means of a signal path 44 consisting of a pair of wires 44a and 44b, and the wire 44b is connected to the ground point 45 common for the apparatus. The other wire 44a is connected to an amplifier 47, preferably via a breaker 46. The output from the amplifier 47 is connected to a so-called phase-locked circuit, consisting of a phase detector 48 and a voltage governed oscillator 49, as well as to a control circuit 50 which includes means and connections (not shown) for controlling the sequence of operations.
The phase detector 48 receives a signal from the amplifier 47 and also a reference signal from the output of the oscillator 49. The oscillator 49 receives its control voltage from the output of the phase detector 48 via a switch 51 and a memory 52. The output of the oscillator 49 can also be connected to the coil 43 via a switch 53 and the conduit 44a, preferably - , ., via a power amplifier (not shown). The mode of operation of the apparatus is as follows: Assume that the oscillating system is in a state of repose and in a state of equilibrium. A first energy pulse is impressed on the oscillating system by impressing a current pulse on the coil 43. This current pulse can be obtained either by a device described above in connec-tion to Figure 3 or by closing the switch 53 in the embodiment of Figure 4.
Immediately after the energy pulse is over, switch 53 opens and switches 46 and 51 close. The switch 54 is open. The mechanically oscillating system 42 generates in the coil 43 a voltage which, via the signal path 44, is conducted to the amplifier 47, and a signal representing the oscillation state of the system is obtained on the output of the amplifier. This signal is conducted to one of the inputs of the phase detector 48. The other input of the phase detector is energized from the output of the oscillator 49 which is constructed such that its frequency is lying near to the frequency of the oscillating system. The signal from the phase detector will represent the phase differences between the signals impressed on the two inputs and thereby also the frequency difference between these signals. This signal from the phase detector is conducted back to the osclllator 49 vla the switch 51 and the signal-following memory 52, so that the frequency of the oscillator changes in a direction equivalent to the frequency generated by the oscillating system. The memory 52 is assumed to contain means necessary for the stability of this control clrcuit, for instance filters. After ad~ustment of the frequency for the oscillator 49 this frequency will coincide with the frequency generated by the oscillating system 42 and, furthermore, will be lying in a determined phase relation relative to this latter frequency. After a certain time, determined by the control means included in the control circuit 50, for instance time circuits, counting circuits and circuits sensing the signal level or combinations of these circuits, a signal is delivered for generating an energy pulse to the .~
-~ 1084595~
oscillating system. At this point in time the switch 51 opens and the frequency of the oscillator 49 remains at a value lt had before the switch was opened. Immediately after this the switch 46 opens at the same time as switch 54 closes, thereby making it possible for the control circuit 50 to receive information about the signal from the oscillator 49. In an appro-priate state for the signal from the oscillator 49, the switch 53 receives a signal from the control circuit 50 and closes, and an energy pulse, the length of which is determined by the control circuit 50, is impressed on the oscillating system via the coil 43. Immediately after the termination of the energy pulse the switches 46 and 51 close and the switch 54 opens. By this apparatus, in which the phase-locked circuit is an essential part, a feeding of the energy pulse into the oscillating system is ensured in such a phase state, that interferences in the oscillation of the system are prevented. The frequency generated in the oscillating system will be ; reproduced on the output of the oscillator 49 as soon as the phase-locked circuit has locked. Thus, the frequency variations of the oscillator 49 is a measure of the primary measurement function affecting the oscillating system 42. The var:Lation in the measurement function can also be taken out as an analog signal from the output of the phase detector 48, preferably after appropriate low-pass filtering. Owing to the fact that the frequency of the oscillator 49 strictly follows the frequency of the oscillating system 42, except for the short time intervals when the energy pulse is imparted to the oscillating system, the variations of the measuring magnitude can also be followed between the energy pulses without interferencesoccurring on this signal upon energy pulse delivery. Since the phase-locked circuit also operates as a band pass filter, the signal from the oscillator 49 will be free from interferences and furthermore have a high level, which facilitates and simplifies further signal processing. The band width for the filter operation which the phase-locked circuit performs is dependent on the filters ~08~S99 (here assumed to be positioned in the memory 52) being engaged between the output of the phase detector 48 and the control input of the oscillator 49. These filter actions also determine the so-called capture range of the phase-locked circuit, i.e. the largest frequency difference that can exist between the frequency of the oscillator 49 upon the start of the system and the frequency generated by the oscillating system 42. In order to ensure a rapid and secure start of the system, the filter actions must consequently be formed such that this can occur. Such a filter configuration, however, means that the equivalent band width of the filter action of the phase-locked circuit will be comparatively large, which is a disadvantage for the suppression of possible interference signals. The filter action can therefore, according to known technique, be formed with the aid of electron-ically controlled filter elements which are governed via the output of the phase detector 48 and circuits in the control circuit 50 connected to the output in such a manner, that, as soon as the frequency of the oscillator 49 follows the frequency of the oscillating system 42, the parameters for the filter between the output of the phase detector 48 and the input of the oscillator 49 are changed in such a direction that the equivalent band width of the phase-locked circuit decreases.
Naturally, the above described method with references to Figures 3 and 4 can be combined with the method described in connection to Figure 2 for decreasing the influence of cable capacitance.
The energy pulse delivered to the oscillating system for maintain-ing its oscillation can be given various form and time extension. A pulse can be used which is of the same form as a multiple of a whole or a half period of the frequency of the oscillating system in order to avoid to the utmost possible extent a non-desired interference of the state of the oscillating system in other respects than the intended amplitude increase.
However, it is desirable, from a measuring technique point of view, to design ``;:` ' ~V84599 the transmitter and its oscillating systems such that a frequency change as large as possible is achievable. In such a case it may be appropriate to use an apparatus of the kind shown in Figure 4 in order to produce a pulse form being equal to a multiple of a whole or a half oscillating period.
In this case it has proved to be advantageous to use a pulse which is short in comparison with the oscillating period delivered to the oscillating system at appropriate points in its oscillating motion.
Within the frame of the present invention, although not shown, it is possible to use the same device for sensing the state of and for delivering energy to a plurality of transmitters by providing a switch between the transmitters and said device in a manner known per se. Moreover, the signal paths in the embodlments described above and shown in the drawings consist of electric wires. However, within the frame of the present invention the signal paths can consist of other transmission means than electric wires, as for instance microwave transmission, acoustic transmission, optical transmission.
.
:
- , : . ~ .
Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for sensing the oscillating state of an oscillating system in a transmitter and for delivering energy to the oscillating system for maintaining the oscillation in the oscillating system, wherein at least one frequency-determinative parameter in the oscillating system is influenced by a measurement function and wherein the sensing of the oscillating state of the oscillating system takes place by means of the same signal path as the delivery of the energy for the maintenance of the oscillation in the oscillating system and that the delivery of energy to said system is in the form of pulses at time intervals longer than a whole period of oscillation in said system.
2. A method according to claim 1, wherein the energy is delivered to the oscillating system during a time period which is shorter than the time passing between the end of one energy delivery and the beginning of the next.
3. A method according to claim 1 and 2, wherein the energy is delivered during a time period which is not longer than a whole period of the oscillation in the oscillating system.
4. A method according to claims 1 or 2 wherein the energy is delivered in pulses the duration of which is essentially shorter than a half period of the oscillation in the oscillating system.
5. An apparatus for carrying out the method according to claim 1, including a transmitter provided with an oscillating system, a signal path connected between the transmitter and means for sensing the oscillation state of the oscillating system, a signal path connected between the trans-mitter and means comprising a separate pulse circuit connected to a control unit for delivering energy for maintaining the oscillation in the oscillating system, and a measuring device connected to the transmitter for affecting the oscillating system by means of at least one frequency-determinative parameter, and wherein said signal path between the transmitter and said sensing means is the same as said signal path between the transmitter and said energy delivering means.
6. An apparatus according to claim 5, wherein said sensing means consists of an amplifier and a control circuit connected thereto, and that said energy delivering means for delivering the energy in pulses consists of a pulse generator.
7. An apparatus according to claim 6, wherein said pulse generator consists of a condenser, a voltage unit, a resistance and a thyristor.
8. An apparatus according to claim 5, wherein said energy delivering means for delivering the energy in pulses consists of an oscillator,
9. An apparatus according to claim 8, wherein said oscillator is connected to said control circuit via phase detector.
10. An apparatus according to claim 5, wherein said energy delivering means in case of continuous delivery of the energy, consists of an oscillator to which a measuring means is connected.
11. An apparatus according to claim 5, wherein the oscillating system of the transmitter consists of a mechanically oscillating system.
12, An apparatus according to claim 11, wherein said mechanically oscillating system consists of a bending-resistant band mounted for oscillation between fixed ends.
13. An apparatus according to claim 12 wherein said band has a curved shape between its fixed ends.
14. An apparatus according to claim 5 wherein the oscillating system of the transmitter consists of an electrically oscillating system.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7600912A SE400385B (en) | 1976-01-28 | 1976-01-28 | PROCEDURE FOR SENSING IN A SWINGING SYSTEM IN A METHODER SENSING THE SWITCH STATE OF THE SYSTEM AND DEVICE FOR PERFORMING THE PROCEDURE |
| SE7600912-5 | 1976-01-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084599A true CA1084599A (en) | 1980-08-26 |
Family
ID=20326837
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA270,475A Expired CA1084599A (en) | 1976-01-28 | 1977-01-26 | Detection and maintenance of oscillations |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4257010A (en) |
| JP (1) | JPS52113240A (en) |
| AU (1) | AU508786B2 (en) |
| CA (1) | CA1084599A (en) |
| CH (1) | CH615505A5 (en) |
| DE (1) | DE2703200A1 (en) |
| FR (1) | FR2339904A1 (en) |
| GB (1) | GB1573739A (en) |
| SE (1) | SE400385B (en) |
Families Citing this family (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4118977A (en) * | 1976-10-13 | 1978-10-10 | The Foxboro Company | Electric signal transmitter for vibrating-wire sensor |
| NL7907407A (en) * | 1978-10-13 | 1980-04-15 | Foxboro Co | INSTRUMENTATION SYSTEM. |
| US4372164A (en) * | 1980-06-02 | 1983-02-08 | The Foxboro Company | Industrial process control instrument employing a resonant sensor |
| DE3107947A1 (en) * | 1981-03-02 | 1982-09-16 | Vdo Adolf Schindling Ag, 6000 Frankfurt | DEVICE FOR TRANSMITTING A MEASURED VALUE FROM A MOVING OBJECT TO A RELATIVE TO THIS FIXED OBJECT |
| US4470313A (en) * | 1982-04-05 | 1984-09-11 | The Foxboro Company | Mechanically excited resonant-element sensor |
| US4445371A (en) * | 1982-04-30 | 1984-05-01 | Standard Oil Company (Indiana) | Gravity meter and method |
| AT389166B (en) * | 1982-06-01 | 1989-10-25 | Friedmann & Maier Ag | Transducer |
| GB8303587D0 (en) * | 1983-02-09 | 1983-03-16 | Chapman Cash Processing Ltd | Coin discriminating apparatus |
| US4956606A (en) * | 1984-10-17 | 1990-09-11 | Mine Safety Appliances Company | Non-contact inductive distance measuring system with temperature compensation |
| US5210521A (en) * | 1990-07-26 | 1993-05-11 | Gary M. Hojell | Vehicle alarm apparatus and method for preventing injury to nearby persons |
| JP2658592B2 (en) * | 1991-01-30 | 1997-09-30 | 日本電気株式会社 | Oscillation stop detection circuit |
| DE10025561A1 (en) * | 2000-05-24 | 2001-12-06 | Siemens Ag | Self-sufficient high-frequency transmitter |
| DE60235173D1 (en) * | 2001-07-03 | 2010-03-11 | Face Internat Corp | SELF-SUPPLY SWITCH INITIALIZATION SYSTEM |
| DE10150128C2 (en) * | 2001-10-11 | 2003-10-02 | Enocean Gmbh | Wireless sensor system |
| FR2845265A1 (en) * | 2002-10-08 | 2004-04-09 | Cognis France Sa | The apparatus to test skin reactions and/or hypersensitivity uses electrodes at the skin, together with a separate reference electrode, to register the neural electrical activity when under stress or attack |
| US20040174287A1 (en) * | 2002-11-21 | 2004-09-09 | Deak David G. | Self-contained switch |
| US9343931B2 (en) | 2012-04-06 | 2016-05-17 | David Deak | Electrical generator with rotational gaussian surface magnet and stationary coil |
| US11251007B2 (en) | 2017-10-30 | 2022-02-15 | Wepower Technologies Llc | Magnetic momentum transfer generator |
| US11159124B2 (en) * | 2020-03-09 | 2021-10-26 | Biosense Webster (Israel) Ltd. | Sine-wave generation using pulsed D-class amplifier |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3140462A (en) * | 1961-06-28 | 1964-07-07 | Gordon B Hayes | Transducer |
-
1976
- 1976-01-28 SE SE7600912A patent/SE400385B/en not_active IP Right Cessation
-
1977
- 1977-01-19 US US05/760,800 patent/US4257010A/en not_active Expired - Lifetime
- 1977-01-21 GB GB2655/77A patent/GB1573739A/en not_active Expired
- 1977-01-26 CA CA270,475A patent/CA1084599A/en not_active Expired
- 1977-01-27 FR FR7702228A patent/FR2339904A1/en active Granted
- 1977-01-27 DE DE19772703200 patent/DE2703200A1/en not_active Withdrawn
- 1977-01-27 AU AU21728/77A patent/AU508786B2/en not_active Expired
- 1977-01-27 CH CH100677A patent/CH615505A5/de not_active IP Right Cessation
- 1977-01-28 JP JP859277A patent/JPS52113240A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| SE7600912L (en) | 1977-07-29 |
| FR2339904A1 (en) | 1977-08-26 |
| SE400385B (en) | 1978-03-20 |
| FR2339904B1 (en) | 1983-03-18 |
| GB1573739A (en) | 1980-08-28 |
| US4257010A (en) | 1981-03-17 |
| JPS52113240A (en) | 1977-09-22 |
| DE2703200A1 (en) | 1977-08-04 |
| AU508786B2 (en) | 1980-04-03 |
| CH615505A5 (en) | 1980-01-31 |
| AU2172877A (en) | 1978-08-03 |
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