US 3920961 A
A digital timer for monitoring flow time through an orifice of a fluid sample having particles suspended therein. The digital timer includes means for presetting a sample flow time and means for providing an alarm when the flow time is greater than the preset time. The timer further includes means for automatically providing a validating signal to indicate that the apparatus has functioned properly and means for measuring digitally the preset time calibration.
Description (OCR text may contain errors)
United States Patent Berg 1 1 Nov. 18, 1975 1 1 DIGITAL TIMER 3,636.549 1/1972 Berman et a1 235/92 T ll 1. 235 92 PC  Inventor: Robert H. Berg, 196 Clinton, 3 657 725 4/1972 I Esta e a Elmhurst, 111. 60126 7 J h M Th J Primary Examiner osep esz, r.  Ffled' 1973 Attorney, Agent, or Firm-Hill, Gross, Simpson, Van [.21] App]. No.: 386,219 Santen, Steadman, Chiara & Simpson Related US. Application Data A I  Continuation of Ser. No. 166,766. July 28, 1971,  ABSTRACT abandoned.
A digital timer for monitoring flow time through an  US. Cl. 235/92 T; 235/92 PC; 235/92 R; orifice of a fluid sample having particles suspended 324/71 CP therein. The digital timer includes means for preset-  Int. Cl. G06M 11/00 ting a sample flow time and means for providing an  Field of Search 235/92 PC, 92 T, 92 PE, alarm when the flow time is greater than the preset 235/92 EA, 92 FL; 324/71 CP; 340/239, time. The timer further includes means for automati- 243; 73/55, 56 cally providing a validating signal to indicate that the apparatus has functioned properly and means for mea-  References Cited suring digitally the preset time calibration.
UNITED STATES PATENTS 6 Cl 3 Dr F, 3,074,266 l/1963 Sadler et al 73/55 alms awmg gums I AMPLD/SABLE 22 24 27 Y F; 63 F52 60/60 H2 .90 3/ F81 v DIV/D56 29 9,5 96 [5M IL Li Tf/EESHOLD i a I C/ECU/T I 5W? 1 A 8/ l 37 i A9 44 I 39 mums WHEEL II mam/w sw/rcwmssx cou/vrse 1 fi 4/ L j DIGITAL TllMER I y i This is a continuation of application Ser. No. rennet, filed July 28, 1971, and now abandoned. 1
BACKGROUND OF THE INVENTION I use of a microscope or an enlarged microscopic projection to visually, monitor obstructions tosample, flow through an orifice and accordingly discount the data of an operation wherein such a blockage. occurred. The obvious disadvantage of visual observationfresides in the requirement for constant operator observation and even then the possibility that. an operator may miss seeing a temporary orifice blockage. Another technique involves the use of RC timing circuits which involve cut and try settings. The disadvantages of such a technique includejthe temperature sensitivity and aging characteristics of RC timing circuits and the number ofadjustments to be made before an accurate setting may be obtained. An audible method of blockage detection has 1 also been emp loyedwherein anaudible clickof mechanical or electronic display counters is monitored b the operator. This technique suffersfrorn a number of drawbacks including (1) the requirement for an operator to have a sense of rhythm and (2) the possibility that an operator who has such a sense of rhythm will miss a change of cadence just as an operator miss seeing orifice blockage in the aboye-mentionedvisual method. I i A I Still another'blockage detectiontecliriique involves the generation of a signal in response to noise dteetion upon obstruction the orifice by rdebris carriedin, a sample. This method of detection is generallyinflexible and requires the utilization of critically discriminating noise detection circuitryj v i SUMMARY OF THE iNVENTION The primary object of the present invention is to Another object of the invention is to provide a fl exi ble digital timer for measuring sample flow time through an orifice in an electric sensing zone.
Still another object of the invention is to provide a digital timer forsetting a predetermined time operational so that associated article size analysis equipment may be operated on'an exactaliquot of material to per:
tnit normalizing of data. I
According to the inventionfthe foregoing arid other objectives are realized through theprovision of a digital timing circuit which includ es'a clock or time base circuit for deriving Oii'second spaced pulses from a conventional Sit/oi) Hz line waveform. During the timing operation, these pulses are utilized to drive a register system and at tirnesa display counter. In one mode of operation, a norm isdetermined by reading the elapsed time from the display counter ln a second mode of opting the register to remember its count and continue counting during the manometer resetting process whereby after the monitoring operation, the alarm device is energized in the next 0.1 second to provide a validating signal as the register continues to count until the mercury again clears the start contact andresets the register. This will generally sufficeto detect leaks or missetting of the register, butamore certain detection of these possible conditions is the incorporation of an additional control gate i on the validating signal" which would inhibit such signal if no preset time completion' occurred within, say, 0.3 seconds after the mer cury passed from a top to-an unstop level.
Another feature of the invention resides in theprovision of circuit means with the flexibility to control or not control the output to a pulse height analyzer (FHA) of all particle pulses generated between start and'stop,
or all pulses prior to" stop. I
Another feature of the invention resides in' the fleitibility of the digital timer wherein the register may be preset'to' a'rnultiple of the predetermined normal flow time in order to set the sample flow time so that various sample quantities may be monitored without changing the metered volume of the mercury manometer. In this type of operation, however, the alarm signal is not available to indicate blockage 0r validate the opera- 1 .BRI'EF DESCRIPTION OF THE DRAWINGS Other objects,'fea tures and advantages of the invention will best be understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. l'is a schematic block diagram of a particle sensing zone, a current supply to the zone, a pulse height analyzer associatedwith the sensing zone and current supply, and adig ital timer associated with the pulse heightanalyzer and sensing zone apparatus according to the principles of the present invention;
FIG. 2 is a schematic logic circuit diagram of a digital timer constructed in accordance with the principles of the present'invention for use in a system such as illustrated in FIG; I; and
FIG. 3 is a schematic logic circuit diagram of the thumb wheel switch assembly illustrated in FIG. 2.
DESCRIPTiON OF THE PREFERRED EMBODIMENT of the same composition as the electrolyte 11. The ori-,
fice tube 13 includes an orifice 14 for permitting the passage of the electrolyte 11 containing particles into the interior of the tube 13 under the influence of a vacuum.
A current supply 17 is connected to an electrode 15 within the orifice tube 13 and to an electrode 16 within the beaker 10 for establishing a flow of current through the electrolyte 11, 12 by way of the orifice 14. As a stream of particles is caused to traverse the orifice 14, each particle modulates the current flow to provide a pulse having a height which is representative of its size. These particle pulses are detected, amplified and then analyzed by a pulse analyzer 18.
A mercury manometer is also connected to the vacuum and includes a tube 19 having mercury 20 therein which is caused to rise and fall in accordance with the application of the vacuum to engage and disengage a start contact 21 and a stop contact 22 for controlling the operation of the pulse height analyzer 18 during the period of particle sampling.
According to the invention, which will be described in greater detail below, a digital timer 23 is provided and connected to the start and stop contacts 21, 22 for monitoring for orifice blockage. The digital timer 23 is connected to the pulse counter/size analyzer by way of data lines, symbolically illustrated by the lines 24 and 25, for providing information to and receiving information from the pulse counter/size analyzer 18.
Referring to FIG. 2, the manometer 19 with the mercury 20 and the start and stop contacts 21, 22 therein is illustrated in the upper right hand corner of the figure, and the pulse counter/size analyzer 18 is illustrated in the lower right hand corner of the figure. In addition, a display counter 80 and a threshhold counter 81 which are portions of the pulse counter/size analyzing apparatus are specifically illustrated in the lower right hand comer of the circuit.
The major portions of the digital timer illustrated in FIG. 2 are as follows. A time base in 0.1 second increments is provided from a 50 or 60 Hz input by way of a divider 31 which may be, for example, an SN 7490 circuit having the gates 32 and 36 associated therewith for resetting. The output of the divider 31 is by way of the conductor 33 and the division of the line frequency by five or six is accomplished by selectively connecting either the conductor 35 or the conductor 34 to one input of the gate 32. These conductors are connected to the 12th and ninth terminals of the SN 7490 circuit. The sixth, seventh and 10th tenninals of the SN 7490 are connected to ground, the first terminal is connected to the 12th terminal, the 14th terminal is the trigger input 30, the fifth terminal is connected to the supply voltage V, the second and third terminals are connected to the output of the gate 36, and the eighth terminal is connected to the conductor 33. The 11th terminal is not used in this particular application.
The 0.1 second time base pulses are supplied by way of the conductor 33 and the conductor 37 to a thumb wheel switch assembly 38 which is illustrated in greater detail in FIG. 3.
The thumb wheel switch assembly 38 is utilized for controlling the lighting of the lamp 65 by way of the transistor 69, the diodes 68, 66 and the gate 63.
A reset-start switch SW is provided for resetting or starting the digital timer in conjunction with the position of a function switch FSW. The remainder of the circuit includes a plurality of gates, inverters, and diodes which function in accordance with the settings of the switches and the position of the mercury with reby way of the conductors 33 and 37 to the thumb wheel spect to the start and stop contacts as will be discussed in detail below.
In FIG. 3, the thumb wheel switch assembly 38 is illustrated as comprising a plurality of serially connected counters or registers 43, 55, 58 having respective trigger inputs 42, 54, 57. These may also be SN 7490 circuits connected substantially in the same manner as the divider 31 with the exception that the 11th terminal is employed for triggering the following stage and/or for encoding purposes by way of the respective thumb wheel switches, such as the switch 52. These switches may be of a type available from lnterswitch Corporation and sold under the assembled switch order code MB-031L-W5. The thumb wheel switches, as can be seen in FIG. 3, encode their respective counters by 0.1, 1.0 and 10.0 second intervals and each includes an output 53, 56, 59 for providing a preset signal by way of the conductor 39 to the gate 63 for controlling the operation of the alarm lamp 65. Encoding is by way of diodes, such as the diodes 48-51.
The timer may be set for four different functional operations, as indicated by the four separate positions of the function switch F SW. In the fourth position wherein the movable contact FS engages the stationary contact FS4, the count registers of the thumb wheel switch function to register the time from start to stop of the mercury metering section. This operation should be performed with clean electrolyte and a very clean orifice in order to establish exactly the required time for sample flow. This will hereinafter be referred to as the normal time. With the function switch in the fourth position and with the mercury column depressed, a volumetric run is initiated causing the mercury 20 to rise and engage the start contact 21. The gate 92 and the gate 36 prevent resetting of the divider 31 and insure an initial reset by way of the conductor 40 of the counter registers 43, 55, 58. The gate 92, the gate 71 and the inverter 72 control the gate and the inverters 96 to permit pulses shaped by the resistors 27, 28 and the zener diode 29 to be applied to the trigger input 30 of the divider 31. Accordingly, the line frequency is divided by five or six, as the case may be, and applied switch assembly for operating the counters 43, 55, 58. At the same time, the ground potential applied to the switch terminal FS4 has caused the gate 76 to be primed for operation by way of the diode 84 and the inverter 86, and the output pulses of the divider 31 are registered in a display counter by way of the gate 76 and the inverter 79. During a run in the fourth position, the thumb wheel switch assembly has the thumb wheel switches 52, 56, 59 set to a value much higher than that expected to be counted in order to prevent the occurence of an alarm; otherwise, the alarm lamp may be ignored during the run.
As the mercury 20 rises and engages the stop contact 22, the gate 71 and the inverter 72 operate to cause the gate 95 and the inverter 96 to prevent the application of the line derived pulses to the divider 31. It should be noted that in position F84, the function switch FSW controls the gate 94 so as to prevent the application of any output to the FHA 18.
As the mercury 20 is again depressed and disengages the contact 22 and then the contact 21, the gate 71 and the inverter 72 again cause the gate 95 and the inverter input 30 of the divider 3 l and the gate 92 permits resetting of the divider by way of gate 36 (and the gate 32).:
With the switch PSW having its contact .PS connected to its contact PS1, and with the thumb wheel switches set to the time measured in the position PS4 plus 0.1 seconds, a runwith-particles suspended in the electrolyte 11 maybe made. Again, as the mercury engages the start contact 21, the gate92 prevents resetting of the divider by way of the gate. 36 and the gate 71 and the inverter 72 cause the gate,95 and the inverter 96 to permit the application oftrigger pulses to the trigger input 30 of the diyider 31. The 0.1 second spaced pulses appear at the output conductor 33 and are extended by way of the conductor 37 to the thumb wheel switch assembly 38. Inasmuch as noground signal is applied to the inverter 86 or to the inverter 87, the gate 76 will be ineffective to' gate the pulses to the display counter 80'; therefore','th 'display counterwill not be exercise d for a visual'display' of elapsed time; however, the gates and diodes 93, 71-73 and 77 via the conductor 75 permit all particle pulses from the'thr'esh old circuit 81 to be counted prior to stop. As the "triercury 20 engages the stop contact 22, the line pulses are again prevented from operating the divider 31 by virtue of the elements 71, 72, 95, 96 and the 0.1 second spaced pulses will not be generated. Therefore, if the lamp 65 has not been energized, the run has taken less time than that encoded in the counters 43, 55, 57 by the thumb wheel switches. If, however, the lamp 65 has been energized, such would occur by way of the output conductors 53, 56, 59 of the thumb wheel switches to extend a signal over the conductor 39 to the gate 63. The gate 63 and the resistor 67 connected to the supply voltage V reverse bias the diode 66 and cause a forward biasing of the diode 68 to render the transistor 69 conductive.
Assuming that the run was performed within the time set on the thumb wheel switches, and that the mercury is caused to be depressed to clear the stop contact 22 and then the start contact 21, first the gate 71 and the inverter 72 cause the gate 95 and the inverter 96 to permit the provision of the time base pulses on the conductor 33. The counters 43, 55, 58 remember the time to which they were exercised during the run and continue to count upwardly from that time until the mercury clears the start contact 21 causing resetting of the divider at the gates 32, 36. The continued running of the counters 43, 55, 58 will cause the count to rise above that preset by the thumb wheel switches so that the conductor 39 is provided with a potential for causing the gate 63, the diodes 66, 68, the resistor 67 and the transistor 69 to energize the lamp 65. This signal is only momentary and causes the lamp to flash thereby providing a validating signal that the circuit has functioned properly during the previous run.
With the function switch PSW having its contact PS engaged with its contact PS2, the same functions apply as in the position PS1 except that the signal output is present only when the mercury is between the start and stop contacts (gates 74, 94). This permits size analysis apparatus to be operated on an exact aliquot of material as a normalizer for data.
With the function switch contact PS engaging the contact PS3, the mercury contacts no longer control the register start-stop, and instead the timer preset value determines how long the particles will be registered. Thus, one would simply leave the vacuum valve open and push the switch SW for resetting the thumb wheel switch assembly whereby upon release, counting will proceed for the preset time. This allows data normalizing on a preset time basis, which in itself may not be of tremendous value; but which also allows one to preset a time that is some multiple of the time measured in position PS4 so that different quantities may be counted without changing the mercury volume section of the apparatus. During such a run which effectively changes the operational test time, one of the prior art methods, such as visual observation, should be employed to guard against false results upon blockage of the orifice. I I
The start contact 21 and the stop contact 22 are connected to control the gate 71 whereby a gate 74 may be operated to provide a gating pulse to the apparatus 18, which pulse has a width equal to the travel time of the mercury between the contacts 21, 22. In the position 4, such a pulse does not occur and theinput to the apparatus 18 is placed at a constant potential inasmuchv as in this position particle pulses may not be generated at all if there is a clean electrolyte.
The threshold circuit 81 responds to particle pulses generated during an operational run and provides indications of such pulses to the gate 77 which extends these pulses to the display counter 80 by way of the inverter 79 in accordance with positions PS2 and PS3 of the function switch. The gate 77 is controlled by way of the conductor connected to an input of the gate 74. The gate 74 is controlled over a diode 73 by way of the inverter 72 and the gate 71, and this circuit is in turn controlled by the start and stop contacts 21, 22. Therefore, according to which position PSI-PS3 the switch FSW is in, particle pulses between start and stop, or all particle pulses before stop, may be registered on the display counter.
In the embodiment of the invention illustrated in the drawings, the gates and inverters were realized by well known 930, 936 and 946 circuits.
Although I have described my invention by reference to a specific illustrative embodiment thereof, many changes and modifications may become apparent to those skilled in the art without departing from the spirit and scope of the invention, and it is to be understood that I intend to include within the patent warranted hereon all such changes and modifications as may reasonably and properly be included within the scope of my contribution to the art.
1. In an apparatus for monitoring the flow rate in a particle analysis system of the type including an orifice tube having an orifice and disposed in an electrolyte and connected in fluid communication with a vacuum source, a mercury manometer also connected to the vacuum source and having a pair of spaced start and stop electrodes to be sequentially engaged and disengaged by the mercury upon application and release of the vacuum, and means for sensing particle flow through the orifice and providing particle pulses in response thereto to particle counting and analyzing equipment, the improvement therein of means for performing a test runwith a clean electrolyte and a clean orifice followed by at least one operational run with an electrolyte having particles suspended therein comprismg:
clock means operable to produce clock pulses;
means for setting said counting means after a test run to a predetermined time count in accordance with the count displayed for the test run; and alarm means connected to said counting means and operated during an operational run to indicate time counts greater than the predetermined time. 2. Apparatus according to claim 1, wherein said alarm means comprises an indicator lamp.
3. Apparatus according to claim 1, wherein said alarm means includes a lamp connected to said counting display means.
4. Apparatus according to claim 1, wherein said means for setting said counting display means comprises:
switch means connected to said counting means and operable to preset said counting means, said switch means including indicia means for providing a visual indicia of the time setting.
5. The apparatus according to claim I, wherein said clock means comprises:
means for connection to an alternating wave electrical supply and operable to shape the wave thereof into pulses having the same periodic occurrence;
a frequency divider connected to said shaping means to divide the frequency of the shaped wave.
6. The apparatus according to claim 5, wherein said frequency divider includes means operable to provide 0.1 second spaced pulses from the input pulse fre quency.