US 3409824 A
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Nov. 5, 1968 G. MAKUH 3,409,824
AUTOMOTIVE IGNITION ANALYZER HAVING LARGE SCREEN PICTURE TUBE Filed April 18, 1966 4 Sheets-Sheet l #l Spark Plug Pickup Horizontal) Power Amplifier s 4 Horizon'lol Amplifier Relroce Blanking r" Power Supply CRT Brighlness Control l 8 L Verhcul Ampllfler L RF vp s pp yw lO 2 4' F 6RD Power Supply J con. a? am I E 20 PLUG ZONE DEE CABLE WDE E PLUG E E G a l5-P| ug E PLUGSa i5 PLUG ZONE G000 a 5 a ACCELERATE AT ACCEL PLUG5 ERATION B a g |O--PLUGS a OLE-l0 OK PLUG ZONE AT IDLE 5 FOULED FOULED 5 PLUG ZONE g o a f G. MAKUH Nov. 5, 1968 Filed April l8, 1966 4 Sheets-Sheet 2 033 20 to o 0:255 823m INVENTOR GEO/96E ATTORNEY 8x85 5 in.
Nov. 5, 1968 G. MAKUH 3,409,824
AUTOMOTIVE-IGNITION ANALYZER HAVING LARGE SCREEN PICTURE TUBE Filed April l8, 1966 4 Sheets-Sheet 3 To Altenotor For Diode Ripple Nov. 5, 1968 MAKUH 3,409,824
AUTOMOTIVE IGNITION ANALYZER HAVING LARGE SCREEN PICTURE TUBE Filed April 18, 1966 4 Sheets-Sheet 4 SCOPE-PRIMARY SUPEWMPOSED PLUG 20 COIL WIRE 20 A C in OFF i 6000 e000 POINTS lS-PLUGS 0ND. COIL CLOSED ACCELERATE -I5 P \TS I PTS I E l0 OPEN POINT DWELL PLUG WIRE4 NORMAL PATTERN 6CYL. 5o 4O 30 20 IO DEGREES o SCOPE SECONDARY EXPANDED PLUG ED WIRE -20 NORMAL PATTERN OFF FOR POS. a NEG. SYSTEMS is PLUGS ACCELERATE --15 A CAP & ROTOR iO'PLUGS OLE "IO 4 I4 I L O INVENTOR 6E06E M44 United States Patent 3,409,824 AUTOMOTIVE IGNITION ANALYZER HAVING LARGE SCREEN PICTURE TUBE George Makuh, Parrna, Ohio, assignor to King Electronics & Manufacturing Corporation, Cleveland, Ohio Filed Apr. 18, 1966, Ser. No. 543,191 14 Claims. (Cl. 32415) The present invention relates to ignition testing devices for internal combustion engines, and is more particularly concerned with an electronic ignition analyzer for automotive engines.
Many forms of apparatus are known in the art for testing ignition systems of automobiles. Such apparatus generally measure and graphically represent the characteristics of the system. More particularly such devices, commonly sample the primary or circuit-breaker voltage and the secondary or sparking voltage of the ignition system. These voltages are applied to an electrostatic cathode ray oscilloscope which provides a visual representation thereof on the screen of the cathode ray tube. By comparing the visual patterns formed with known patterns the operator can immediately analyze and diagnose ignition faults.
Prior art ignition analyzers have invariably utilized Oscilloscopes having electrostatic cathode ray tubes. Such tubes are reliable, can be readily made to provide a linear representation of applied voltages, and operate over a range of ignition frequencies. However, such cathode ray tubes have the disadvantage that they are small, the commonly used tubes having a picture diameter of five to eight inches. Although such tubes are suitable for many purposes, it is desirable to have a large size picture tube in order to provide a more detailed analysis of the wave form of ignition system voltages, and particularly where several people are involved or demonstrations are made to large groups, it is desirable to have a picture tube which forms a picture sufficiently large for all to see even at some distance. Large size electrostatic cathode ray tubes are known, but their cost is prohibitive for most uses.
It is an object of the invention to provide an ignition" analyzer utilizing a magnetic deflection type cathode ray tube. It is a further object to provide such an analyzer wherein the cathode ray tube has a large screen and provides a large image. It is an additional object to provide an oscilloscope having such a picture tube which is relatively free from distortion, and wherein the visual representation is substantially linear to the signalvoltage applied. It is still an additional object to provide an analyzer of the type described wherein the cost of the large picture tube is not prohibitively high. The accomplishment of the foregoing and additional objects will become more fully apparent hereinafter.
According to the invention, an automotive ignition analyzer is provided having means for sampling ignition voltages at both the primary and secondary of the ignition coil and also alternator output system ripple. The signals are suitably amplified and applied to a large screen television tube suitably powered. Filtering or wave shaping circuits are incorporated in the signal amplifier to compensate for non-linearities introduced into the circuit by the coils of the magnetic deflection yoke mounted on the neck of the tube, as well as non-linearities present in the tube itself. The analyzer is provided with a sweep circuit of suitable frequency and having a power amplifier of suitable power capabilities to adequately sweep a simmultaneous representation of the individual firing of all of the spark plugs, and which additionally has suflicient power capability to sweep the field sufliciently so that patterns formed by the firing of only several spark plugs may be alternately spread out over the entire field of the picture tube. As a result a true linear pattern of the spark 3,409,824 Patented Nov. 5, 1968 ice plug discharges as well as the primary coil voltages is projected on the picture tube in such dimensions that it may readily be seen even by persons standing a considerable distance from the tube. The filter or shaping circuit is also so designed that the vertical representation of applied voltage is substantially linear even at high sparking voltage frequencies. Additionally, patterns representative of the operation of alternator systems having a three phase diode rectifier system may be analyzed to determine open or shorted diode condition or three phase winding defects.
The invention in its preferred embodiment is illustrated by the accompanying drawings in which:
FIG. 1 is a schematic block diagram of the ignition analyzer of the invention.
FIG. 2 is a schematic circuit diagram of the horizontal sweep signal generator and the horizontal sweep signal amplifier.
FIG. 3 is a schematic circuit diagram of the vertical amplifier.
FIG. 4 is a schematic view illustrating the pattern obtained of the superimposed primary ignition discharge.
FIG. 5 illustrates the normal expanded pattern obtained from an impulse of a secondary spark discharge, and
FIG. 6 is a parade pattern obtained of the secondary while using only the impulse from the first spark plug to actuate each sweep.
Reference is now made to the accompanying drawings for a better understanding of the invention, wherein all the parts are numbered and wherein the same numbers are used to refer to corresponding parts throughout.
In the description which follows, the values for the components are not given where the circuits are conventional and suitable values are known or may be readily determined by those skilled in the art. However, where component values are critical and are not conventional, representative values will be given.
Referring to FIG. 1, the apparatus is illustrated in block diagram and comprises a magnetic deflection type cathode ray tube 1 such as a common television picture tube (23EYP4). High voltage is applied to the tube by a radio frequency high voltage power supply 2. The horizontal sweep signal is provided by means of a horizontal signal generator 3 incorporating a voltage amplifier and a horizontal power amplifier 4. A low voltage power supply 5 powers the horizontal signal generator 3, the horizontal power amplifier 4, and the picture tube 1. The signal output from the horizontal power amplifier is fed to the horizontal coils of a deflection yoke 6 mounted on the neck of the cathode ray tube 1. The horizontal signal generator may be actuated by any spark plug for a parade pattern display providing one horizontal sweep pulse for each rotation of distributor or by the distributor primary or secondary output circuit which provides one horizontal sweep pulse for each plug firing cycle for superimposed display. Vertical deflection is provided by means of a vertical amplifier 8 having its output connected to the vertical coils of the deflection yoke 6. The input of the vertical amplifier 8 is selectively connected to the high tension output of the ignition coil by means of a capacity coupler or pickup 9, or connected to the distributor primary terminal 10.
The deflection yoke should preferably be of the type commonly termed a cosine yoke, that is, a yoke wherein the horizontal and vertical coils are wound so that their thickness increases as the cosine of the angle from vertical or horizontal subtended by the coil windings. This arrangement prevents the type of picture distortion commonly known as the pin cushion effect.
Referring to FIG. 2, the horizontal sweep signal generator comprises a pulse amplifier 15, which may be a 12AX7 vacuum tube, connected through a coupling con- 3 denser 16 and resistor 17 to a Thyratron (2D2l) 18 which generates a saw-tooth signal. The signal is applied to a 6DX8 width control tube 19 and 19a for controlling the width of the sweep. The output from the width control tube is then applied to the grid circuit of the power amplifier stage.
The pulse amplifier is provided with associated components for supplying proper power requirements including resistors 20, 21, 22, 23, 24, and 25, and capacitor 26. The Thyratron 18 is provided with resistor 27 and condensers 28 and 29. The width control tube 19 and 19a is provided with resistors 30, 31, 32, and 33 and variable resistors 34 and 35. Diodes 36 and 37, and capacitors 38, 39 and 40 complete the circuit components associated with the width control tube.
The circuitry for selectively connecting the horizontal sweep signal generator to the primary or secondary comprises a selector switch 41 having the selector terminal connected to the input of the pulse amplifier 15 through coupling means comprising a resistance 42 and capacitor 43. One terminal 44 of the switch 41 is connected to the primary breaker of the distributor by means of a coupling condenser 45. Associated circuitry comprises a diode 46, a neon lamp 47, and a resistor 48 connected to the ground terminal of the primary of the coil through a resistor 49. The second terminal 50 of the switch 41 is connected to a coupling means which is in turn connected to any spark plug, generally the first spark plug in firing order, and comprises a coupling transformer 51, capacitors 52, 53, and 54, and a resistor 55. When the switch 41 is connected to the primary by the circuit shown, the impulse amplifier is triggered by a signal produced when each spark plug is fired. Consequently, the pattern produced on the picture tube is a superimposed series of curves, one curve produced by the firing of each spark plug placed over the preceding cycle. When the switch 41 is placed in the other position and connected to the terminal 50, only the firing of the one spark plug actuates a horizontal sweep signal, and, consequently, the pattern produced on the picture will provide a parade pattern of all the individual spark plug firing cycles.
Also shown in FIG. 2 is the horizontal sweep signal power amplifier. The basic circuit shown is that commonly known as the Ultra-linear or the Williamson type. Other high power linear power amplifiers available in the art may be used, including amplifiers utilizing solid state components such as semi-conductors. The prime requirements are that the output signal must be highly linear with respect to the input signal and, further, that the power output capability must be sufiicient to cause a very wide excursion scanning beam. The beam excursion must be sufficiently great so that when the apparatus is so adjusted that all the spark plug firing cycles are visibly represented on the picture tube screen in a parade pattern, it must be possible to expand the pattern to display one or more firing cycles over the entire screen area. It has been found that the amplifier shown which has an output capability of about 25 peak watts at low pulse frequencies is sufiicient to provide the necessary beam excursion magnitude.
The output from the pulse amplifier 15 is applied through a potentiometer 60, associated resistors 60a and 60b, and coupling condenser 61 to the power amplifier 4. The amplifier comprises a pentode-triode vacuum tube 62 (6AN8) serving as a dual voltage amplifier tube. The associated circuitry comprises cathode resistors 63, 64 and 65 and plate series resistors 66 and 67. The associated plate filter circuitry comprises capacitor 68, and series resistor 69. The output from the pentode section tube 62 is applied through coupling condenser 75 to the grid of the triode section of tube 62, which serves as a paraphase voltage amplifier and phase inverter. Associated circuitry therewith are grid bias resistor 78, cathode resistors 64 and 65, and plate voltage dropping resists; 67.
The output of the tube 62 is applied through coupling condensers 83 and 84 and grid resistors 85 and 86 to a pair of power amplifier tubes 87 and 88, which may be chosen from such types as 6CA7, 807, EL-34, etc. Associated circuitry with the power amplifier tubes are grid bias resistors 90, 90a, 90b and 91, 91a, 91b 'a balancing potentiometer 92, grid capacitor 93 and cathode bias resistors 94 and 95. A negative grid bias voltage is applied through potentiometer 96. A portion of the output signal is applied through a coupling condenser 97 to the grid of the cathode ray tube for actuating retrace beam blanking. The output from the power amplifier tubes 87 and 88 is applied to an output transformer 100, which may be any suitable high-fidelity output transformer designed for the Williamson or Ultra-linear circuits, as for example A-8072 (Chicago), TO-300 (Acrasound), or A-420 (Dynaco). A portion of the output signal of the transformer 100 is applied through a resistance 101 to the cathode of the first section of the voltage amplifier tube 62, the signal functioning as negative feed-back to cancel or minimize harmonic distortion. The major portion of the signal from the output transformer 100 is applied to the horizontal coils 103 of the yoke mounted on the neck of the cathode ray tube 1. Suitable filament and plate current for the amplifier is supplied from a standard power supply 5 comprising a suitable transformer, a rectifier tube such as a SR4 or a 5V4, or silicon diodes, filter condensers, a filter choke, and resistor.
Referring to FIG. 3, a schematic diagram of the vertical amplifier is shown comprising twin-triode voltage amplifier tubes and 110a and a pentode power amplifier tube 111. The vertical amplifier is the most critical part of the ignition analyzer of the present invention. This is a result of the fact that ignition sparking comprises damped waves of rather high frequencies. When an electrostatic cathode ray deflection tube is utilized in an ignition analyzer, an ordinary amplifier may be used which has good linearity, the pattern shown on the screen of the tube being representative of the spark impulses applied to the amplifier input. However, it has been found that when the output of such a linear amplifier is applied to the coils of the deflection yoke of a magnetic cathode ray deflection tube, the signal is so distorted by the magnetic coils as well as associated circuitry that the pattern produced on the tube is completely unrepresentative of the spark signal applied to the amplifier. According to the invention, it has been unexpectedly discovered, that if proper tube operating characteristics and wave-shaping filters are incorporated into the circuit of the vertical amplifier to provide selective frequency amplification of the proper wave form and magnitude, to compensate for any distortion introduced by the deflection yoke, the result is that the pattern formed on the picture tube is gepresentative of the spark signal applied to the ampli- Because of the criticality of the values of the components, a set of values for a particular amplifier which may be utilized with a particular picture tube (23EYP4) will be set out. However, it is to be understood that when other amplifiers or other picture tubes are used, the re quired values may be somewhat different. In each case, the values may be properly modified by one skilled in the art until a representative pattern is produced.
A signal for actuating the vertical amplifier is obtained by means of a capacity pickup 9 having one end 112 adapted to be inserted into the distributor cap center terminal socket, and the other end 113 is connected to the high tension terminal of the ignition coil. The signal from the pickup 9 is applied through a shielded lead 9a to the intermediate point of a capacitance divider comprising a capacitor 114 having a value in the range of about DOGS-.003 mf., a suitable value being .001 rnf. This capacitor is by-passed by a resistor 115 of 3.9 megohms. A variable capacitor 116 of about 15-80 rnmf.
by-passed by a resistor 117 of 2.2 megohms completes the divider. The capacitor 116 is variable to provide calibration of the signal. This arrangement provides calibration in the range of kv. To provide 'kv. calibration, a second variable capacitor 150 of a range similar to that of the capacitor 116 and a resistor 151 are switched into the circuit by means of a switch 152. The outer terminals of the capacitor 116 and resistor 117 are connected to a voltage divider network comprising a resistor 118 of 330K ohms, and a resistor 119 of 10K ohms. The outer end of the resistor 119 is connected to the grid of the first triode of the twin-triode tube 110. Plate current is applied to the plates of the tube through conventional dropping resistors and 126. The plate of the first triode is coupled to the grid of the second triode through a capacitance-resistance network comprising a coupling condenser 127 having a suitable value in the range of about .010.5 mf., and preferably .02 mf., and a resistor 128 having a value in the range of 470K ohms1.5 megohms, and preferably 1 megohm. Both of the cathodes of the tube 110 are provided with low frequency bypass filters, one comprising a variable resistor 129 of 4K ohms maximum, and a capacitor 130 of .005 mf., and a second filter comprising a variable resistor 131 of 8K ohms maximum and a capacitor 132 of .0005.003 mf., and preferably .001 mf.
The output signal from the plate of the second triode is applied to an intermediate point of another capacitance divider comprising a capacitor 133 of about .0005-.00 3 mf., and preferably .001 mf. and a second capacitor 134 of about .01.05 mf., and preferably .02. mf. The signal passing through the capacitor 134 is applied to one terminal of a switch section 135b which is so connected as to choose alternatively signals from the voltage amplifier tube excited by the spark plug secondary signal or from the voltage amplifier tube excited by the primary signal. The center terminal of the switch is connected to the control grid of the power amplifier tube 111.
In the preferred embodiment, a separate twin-triode voltage amplifier tube 110a is used to amplify the signal from the alternator for diode ripple testing and from the primary of the ignition coil. The values of the fixed components are substantially the same as the corresponding components associated with the secondary amplifier tube 110. The only difference is that the variable components are adapted to be set at such values as to compensate for the lower signal input of the primary and alternator current. The circuit comprises a capacitance divider made up of a capacitor 153 of about .005.003 mf. and preferably .0004 mf. and a capacitor 154 of about .01.05 mf., and preferably .047 mf. A resistance 155 of about 6.2 megohm bypasses the capacitor 153. An input variable capacitor 156 having a range of 8-15 mmf. is bypassed by a resistor 157 of about 47K ohms. The capacitor 156 and resistor 157 are connected to the distributor primary. A resistor 158 of about 510 ohms may be advantageously utilized in the ground return circuit. The wave shaping filter comprising the capacitors 153, 154, and 156 and resistors 155 and 157 is connected to a switch 135a, which alternatively selects connection to the alternator for a diode ripple test, through a coupling capacitor 159 and through a grid bias divider comprising a resistor 160 of about 330K ohms and a resistor 161 of about 10K ohms to the grid of the first triode section of the tube 110a. The cathodes of the tube are provided with a variable grid bias resistor 162 of about 10K ohms and a variable grid bias resistor 163 of about 3K ohms. 'It has been found that for proper operation the resistor 162 is advantageously set at about 6.5K, and resistor 163 is advantageously set at a value of about 500 ohms. In contrast, the resistor 131 of the tube 110 of the secondary amplifier, is advantageously adjusted to 8K ohms and the resistor 129 adjusted to 4K ohms. The associated plate circuitry of. the tube 110a comprises plate voltage dropping resistors 164 and 165 of about 47K ohms, a capacitor 166 of about 20 mf., a resistor 167 of about 3K ohms, a capacitor 168 of about .02 mf. and a resistor 169 of about 1 megohm. The output from the second plate of the tube 110a is applied to a capacitance divider comprising a capacitor 170 of about 01-05 and preferably .02 mf., and a capacitor 171 of about .0005-.003 and preferably .001 mi. This capacitor divider completes the wave shaping filter for the circuitry associated with the tube 110a. A switch section 135b, associated with switch 135 and 135a selectively switches either the primary amplifier or secondary amplifier to the control grid of the :power amplifier tube 111.
The components associated with the power output tube 111 are conventional and include a grid bias resistor 140, cathode bias resistors 141 and 141a, and a screen grid voltage dropping resistor 142. An additional bias regulator may be introduced when the secondary signal is being sampled by means of a switch 135d and comprises a variable resistor 172, a fixed resistor 173 connected to a negative bias voltage source, and a capacitor 174. The output signal from the output tube 111 is applied to the primary of an output transfonmer 143 (Merit #2815), the secondary of which is connected to the vertical yoke deflection coils 144, the secondary being bypassed by a capacitor 145. A switch 1350 may selectively connect the vertical yoke to selective taps on the secondary coil of the transformer 143 to reduce the signal strength when the secondary current of the ignition coil is being sampled.
In adjusting the values of the critical components of the vertical amplifier for proper operation, the following should be observed. The cathode variable resistors 129 and 131 should be adjusted for proper gain and wave form. The values of the capacitors 130 and 132 are selected for minimum low frequency response and maximum sparking signal gain. The calibration trimmer capacitor 116 is adjusted for proper height of the high voltage vertical lines. The value of capacitor 114 is chosen for proper loading of the pickup 9. The values of the capacitors 127 and 133 are selected for correct response and Wave shape of the spark line and size of the high voltage spikes. Diminishing the value of the capacitor 127 drops the height of the spark line. The capacitor 133 is used to provide solid vertical 'high voltage spike lines, in the absence of which capacitor the lines contain bright flashes or dots.
FIGS. 4-6 illustrate various patterns which may be obtained by means of the ignition analyzer of the invention. The patterns themselves are well known in the art and need not be discussed in detail. The present in vention provides the advantage that the patterns may be spread out on a large picture tube such as a 17" to 23" television picture tube, so that the patterns are of greater size and greater brilliancy, and may be readily seen even in bright light. Moreover, because the patterns are magnified, greater detail in the individual curves may be observed.
FIG. 4 illustrates a normal superimposed pattern obtained by connecting the primary of the ignition coil to the vertical amplifier, actuating the horizontal sweep by the ignition impulse of each spark plug. The result shown in the figure is a superimposed pattern of the firing of all plug cycles.
FIG. 5 shows a curve of a normal superimposed secondary pattern.
FIG. 6 shows a curve obtained with the sweep signal actuated by any single spark plug firing. Here individual patterns for .all the plugs are shown simultaneously or in parade. The particular patterns shown illustrate both normal and abnormal condition caused by defects in plugs, cables or distributor.
The present invention has several advantages over ignition analyzers of the prior art utilizing electrostatic cathode ray tubes. First, all the various patterns which can be obtained by means of an electrostatic tube can also be obtained by means of the television picture tubes utilized by the invention. The use of a television picture tube permits a greatly enlarged screen and thus a greatly enlarged pattern for easier viewing and for study in greater detail. The trace is brighter and consequently it is not necessary to place enclosures such as a hood or shade around the tube when it is used in a bright room, which measures are often necessary when an electrostatic tube is used. Further, since television picture tubes are produced in large quantities, a large picture tube can be obtained at modest cost. Further, because of the selected shaping filters utilized in the vertical amplifier, discharges of high sparking voltage frequencies may be recorded which are accurate pictures of the original spark discharge signal, even when utilized with deflection yokes.
Although the invention has been described in a single embodiment utilizing thermionic vacuum tubes for the various functions such as saw-tooth signal generation and amplification, it is of course to be understood that these devices may be replaced by suitable solid state devices performing the same functions, as for example diodes and transistors.
It is to be understood that the invention is not limited to the exact details of construction, operation, or exact materials or embodiments shown and described, as obvious modifications and equivalents will be apparent to one skilled in the art, and the invention is therefore to be limited only by the scope of the appended claims.
1. An ignition analyzer for testing the ignition system of .an internal combustion engine including an ignition coil having primary and secondary circuits and a plurality of spark plugs operatively connected thereto, comprising:
(A) a magnetic deflection type cathode ray tube having a deflection yoke mounted thereon comprising a horizontal deflection coil and a vertical deflection coil,
(B) means adapted to generate a sweeping signal comprising a saw-tooth generator, means for deriving a triggering impulse from an electrical lead of said engine, means for amplifying said triggering impulse and applying said amplified impulse to actuate said saw-tooth generator for producing a single sweeping signal for each triggering impulse,
(C) a power amplifier having its input connected to I said sweeping signal generating means and having its output operatively connected to one of said deflection coils for causing the beam of said cathode ray tube to be swept along one set of coordinates,
(D) an electronic amplifier having its input adapted to be connected alternatively to the primary or secondary of said ignition system and having its output operatively connected to the other of said deflection coils, said amplifier having wave shaping means incorporated therein for correcting the distortion introduced by the characteristics of said deflection coils at the frequencies of oscillations caused by an ignition spark discharge, whereby the visual tracing produced on the screen of said cathode ray tube is a true representation of the signal currents applied to said amplifier.
2. An ignition analyzer according to claim 1 wherein the wave shaping means of said amplifier (D) comprises a. capacitance divider having a pair of capacitors in series connection, the outer end of one capacitor being connected to ground, the outer end of the other capacitor being connected to the input of the first amplifier means of said amplifier, and the intermediate common connection to the capacitors of said capacitance divider being adapted to be connected to an ignition signal generating means.
3. An ignition analyzer according to claim 2 wherein said capacitor connected to ground has a value of about 0001-003 mf., and said capacitor connected to the input 8 of said first amplifier means has a value in the range of about 1.5 to mrnf.
4. An ignition analyzer according to claim 1 wherein said amplifier (D) comprises a plurality of amplifying means, a first capacitance divider comprising a pair of capacitors in series connection having the end of one capacitor connected to ground, the end of the other capacitor connected to the input of the first amplifier means, and the common point intermediate said capacitors adapted to be connected to the ignition signal generating means, and a second capacitance divider comprising a pair of series-connected capacitors having the outer end of one capacitor connected to ground and the outer end of the other capacitor connected to the input of said second amplifier means, and the common point intermediate said capacitors being connected to the output of said first amplifier means, the values of said capacitors being so chosen as to compensate for non-linearities introduced by the deflection coils of said yoke and picture tube, whereby a true representation of the signal voltage applied to said amplifier is provided by the trace on said picturetube.
5. An ignition analyzer according to claim 1 wherein said amplifier (D) comprises at least three amplifying means, a first capacitance divider comprising a pair of capacitors in series connection having the outer end of one capacitor connected to ground, the outer end of the other capacitor connected to the input of the first amplifying means, and the common point intermediate said capacitors adapted to be connected to the ignition signal generating means, and a second capacitance divider comprising a pair of series-connected capacitors having the outer end of one capacitor connected to ground and the outer end of the other capacitor connected to the input of said third amplifying means, and the common point intermediate said capacitors being connected to the output of said second amplifying means, the values of said capacitors being so chosen as to compensate for non-linearities introduced by the deflection coils of said yoke and said picture tube, whereby a true representation of the signal voltage applied to said amplifier is provided by the trace on said picture tube.
6. An ignition analyzer according to claim 5 wherein in said first capacitance divider said capacitor connected to ground has a value of about DOGS-.003 mf., said capacitor connected to the input of said first amplifying means has a value in the range of about 1.580 mmf., and wherein in said second capacitance divider said capacitor connected to ground has a value of about DOS-.003 mi. and said capacitor connected to the input of said third amplifying means has a value of about .0l.05 mi.
7. An ignition analyzer according to claim 5 wherein a resistance-capacitance filter is provided in the cathode circuit of each of said first and second amplifying means adapted to increase low frequency response.
8. An ignition analyzer according to claim 7 wherein the capacitor of each resistance-capacitance filter has a value of about .0005-.003 mf.
9. An ignition analyzer according to claim 8 wherein the resistance in the cathode circuit of said first amplifier means is adjusted to a value of about 8K ohms and the resistor in the cathode circuit of said second amplifying means is adjusted to a value of about 4K ohms.
10. An ignition analyzer according to claim 1 wherein the input of said electronic amplifier (D) is additionally adapted to be connected to an electrical current generating means of said ignition system.
11. An ignition analyzer according to claim 10 wherein said electrical current generating means is an alternator.
12. An ignition analyzer according to claim 10 wherein said triggering impulse is derived from a spark plug of said engine.
13. An analyzer for testing the electrical current gen- 9 erating means of an internal combustion engine comprising:
(A) a cathode ray tube having means for providing both horizontal and vertical deflection,
(B) means adapted to generate the sweeping signal comprising a saw-tooth generator, means for deriving a triggering impulse from the electrical ignition system of said engine, means for amplifying said triggering impulse and applying said amplified impulse to actuate said saw-tooth generator for producing a single sweeping signal for each triggering impulse,
(C) amplifier means having its input connected to said sweeping signal generating means and its output operatively connected to said means for providing 15 deflection of the beam of said cathode ray tube along one set of coordinates,
(D) an electronic amplifier having its input adapted to be connected to the output of said electrical current generating means, and its output operatively connected to said means for providing deflection of said beam along the other set of coordinates.
14. An analyzer according to claim 13 wherein said 5 triggering impulses are derived from one of the spark plugs of said engine.
References Cited UNITED STATES PATENTS FOREIGN PATENTS 11/ 1955 Great Britain.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,409,824 November 5, 1968 George Makuh It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:
Column 1, line 16, "particularly such devices," should read particularly, such devices Column'5, line 17, ".01-0.S mf" should read .0l-.O5 mf line 50, BOOB-.003 mf should read .O00S-.O03 mf Co1umn8, line 49, HUGS-.003 should read .00OS-.003
Signed and sealed this 10th day of March 1970.
WILLIAM E. SCHUYLER, JR.
Commissioner of Patents Edward M. Fletcher, Jr.