US3755687A

US3755687A - Pulse generator

Info

Publication number: US3755687A
Authority: US
Inventors: L Garnett
Original assignee: Deutsche ITT Industries GmbH
Current assignee: TDK Micronas GmbH; ITT Inc
Priority date: 1972-03-30
Filing date: 1972-03-30
Publication date: 1973-08-28
Anticipated expiration: 1990-08-28

Abstract

A total volume flowmeter including a fluid motor to in series a light chopper between a light emitting diode and a phototransistor connected in a pulse transmitter. Regenerative feedback is provided from the phototransistor to the light emitting diode. That is, the light output of the light emitting diode is increased as the illumination of the phototransistor is increased, and vice versa. This makes it possible to use high gain amplification because it produces a hysteresis which discriminates against false output pulses which would otherwise occur with the use of high gain amplification because of vibration induced by external means. A source of potential and a resistor may be connected inseries with the pulse transmitter, both the source of potential and the resistor, if desired, being positioned at a remote location. A pulse counter is connected across the resistor to an indicator which, if desired, may be calibrated in total volume flow.

Description

United States Patent [191 Garnett Aug. 28, 1973 1 1 PULSE GENERATOR [75] Inventor: Lawrence Taylor Garnett, Fullerton,

Calif.

[22] Filed: Mar. 30, 1972 [21] Appl. No.: 239,528

[52] US. Cl 307/117, 307/106, 250/205 [51] Int. Cl. H03k 3/00 [58] Field of Search 307/106, 117;

[56] References Cited UNITED STATES PATENTS 3,631,250 12/1971 Van Buskirk 2.50/205 1,475,583 11/1923 Hoxie 250/233 3,117,459 1/1964 Schweitzer 74/231 C X 2,623,389 12/1952 Van Oosterom 250/233 X 3,562,534 2/1971 Jarrett et a1. 250/205 2,636,478 4/1953 Smyser 121/67 3,322,959 5/1967 Lorenz 250/205 FOREIGN PATENTS OR APPLICATIONS 1,468,223 12/1966 France 200/11 DA OUTPUT C/RCU/ T Primary Examiner-Robert K. Schaefer Assistant Examiner-M. Ginsburg Attorney-C. Cornell Remsen, Jr.. Thomas E. Kristofferson et a1.

[57] ABSTRACT A total volume flowmeter including a fluid motor to in series a light chopper between a light emitting diode and a phototransistor connected in a pulse transmitter. Regenerative feedback is provided from the phototransister to the light emitting diode. That is, the light output of the light emitting diode is increased as the illumination of the phototransistor is increased, and vice versa. This makes it possible to use high gain amplification because it produces a hysteresis which discriminates against false output pulses which would otherwise occur with the use of high gain amplification because of vibration induced by external means.- A source of potential and a resistor may be connected inseries with the pulse transmitter, both the source of potential and the resistor, if desired, being positioned at a remote location. A pulse counter is connected across the resistor to an indicator which, if desired, may be calibrated in total volume flow.

6 Claims, 11 Drawing Figures M'CHQ/V/CQL.

PAIENTEflmze ma 3; 755L687 sum 10$ 5 MECHANICAL COU/V TE 2.

wo/cn T02 25 I 55 3/ PULSE PULSE Z H 3 COUNTER Zc3 46 i M'CHQN/CAL 44 %7557'52.

OUTPUT c/ecu/r PATENTEUAIJQZBIBH 3755687 SHEEI 2 BF 5 PATENTl-imucze ma V SHEEI 5 0F 5 BACKGROUND OF THE INVENTION This invention relates to devices for detecting illumination passing through one or more apertures in a light chopper or the like, and more particularly, to a high gain photoelectric detection system insensitive to vibration induced by external means.

In the past, it has often been the practice to detect the angular velocity of a rotating member by fixing one or more permanent magnets to a disc which is, in turn, fixed to the output shaft of a displacement-type fluid motor. One or more pickup coils then produce output pulses at a pulse repetition frequency (PRF) which is directly proportional to the fluid motor angular velocity. If these pulses are counted and indicated, such an indication is directly proportional to the total volume of the fluid flow through the motor and an indicator may be so calibrated, if desired.

Unfortunately, for flowmeter and other uses, the employment of magnetic pickups is often undesirable for at least two reasons. One is that the output is a velocity analog where a position detector would be more useful in many cases. Further, magnetic pickups are either very expensive, inoperative or inaccurate when the fluid motor shaft rotates at very low angular velocities. Note will be taken that the magnitude of the voltage induced in the coils is directly proportional to angular velocity of the fluid motor shaft. Thus, at low velocities, the pulse amplitudes are difficult to detect or discern from noise created by voltages induced by vibration or otherwise. Errors thus become inevitable. That is, if the amplifier gain is low, pulses are missed and the flow indication is low. If the amplifier gain is high, noise pulses produce an erroneously high flow indication.

It is also known in the prior art that a photoelectric system can produce a position analog. However, this system suffers from at least one of the disadvantages of the magnetic pickup system. That is, vibration induced by external means can cause erroneous high flow readings when the amplifier gain is high. Further, erroneous low readings occur when the amplifier gain is' low.

SUMMARY OF THE INVENTION In accordance with the system of the present invention, the above-described and other disadvantages of the prior art are overcome by providing a pulse transmitter including a light chopper or the like positioned between a light source and a photoelectric device, regenerative feedback including amplifier means to increase the illumination of the source when the illumination of the device increases, and vice versa.

Although it is unexpected, the use of the regenerative feedback builds in hysteresis so that a high amplifier gain may be used for high sensitivity and accuracy. However, the high gain does not cause the system to indicate inaccurately. This is true because the system of the present invention is no longer sensitive to small axial or angular movements of the light chopper caused by vibration induced by external means or otherwise. This insensitivity is achieved because the regenerative feedback produces the hysteresis. For example, if the light chopper is rotated in one direction to a first position where the output first goes high, the light chopper can then be rotated through a predetermined angle in the reverse direction before the output goes low again, and vice versa.

The system of the present invention will have many applications in many widely diverse fields. It is, therefore, not to be limited to those applications or fields disclosed herein. However, it may be incorporated in a total volume flowmeter as disclosed in detail hereinafter.

The above-described and other advantages of the present invention will be better understood from the following detailed description when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings which are to be regarded as merely illustrative:

FIG. 1 is a diagrammatic view of a flowmeter;

FIG. 2 is a diagrammatic view of a portion of the flowmeter shown in FIG. 1;

FIG. 3 is a vertical sectional view through a pulse transmitter shown in FIG. I;

FIG. 4 is a sectional view of the transmitter taken on the line 44 shown in FIG. 3;

FIG. 5 is a broken away end elevational view of the transmitter shown in FIGS. 1, 3.and 4;

FIG. 6 is a perspective view of a subassembly shown in FIG. 5; a

FIG. 7 is a vertical sectional view through the subassembly taken on the line 7--7 shown in FIG. 6;

FIG. 8 is a vertical sectional view of the subassembly taken on the line 8-8 shown in FIG. 7;

FIG. 9 is a broken away and elevational view of a light chopper constructed in accordance with the present invention;

FIG. 10 is a schematic diagram of a circuit constructed in accordance with the present invention; and

FIG. 11 is a schematic diagram of a current regulating diode shown in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings in FIG. I, a flowmeter is indicated at 20 including a fluid motor 21, a pulse transmitter 22, a mechanical counter-indicator 23, a pulse counter 24 and an indicator 25.

Motor 21 has an inlet conduit 26 and an outlet conduit 27. When fluid is forced into conduit 26, through motor 21, and out of conduit 27, the rotor, not shown in FIG. 1, of motor 2l rotates a light chopper, not shown in FIG. 1, in pulse transmitter 22 by a mechanical connection 28 thereto, as shown in FIG. 1.

Fluid motor 21 may be any conventional fluid motor, but preferably, although not necessarily, is of the positive-displacement type. For example, fluid motor 21 may be identical to or similar to the type disclosed in US. Pat. No. 2,636,478. Other fluid motors are disclosed in U.S. Pat. Nos. 2,636,479; 2,738,775; 2,853,978 and 2,882,868.

In accordance with the foregoing, fluid motor 21 has an output shaft which turns it an angular velocity directly proportional to the rate of fluid flow through motor 21 measured in volume per unit time.

The rotary output shaft of fluid motor 21 is indicated at 29 in FIG. 2 and has a mechanical connection 30 with indicator 23. Indicator 23 may be any conventional revolutions counter or otherwise and is employed to indicate total volume flow close to motor 21 and transmitter 22.

Transmitter 22 has

output terminals

31 and 32, as shown in FIG. 1, to which leads 33 and 34 are connected, respectively. An assembly 35, including counter 24 and indicator 25, may be located at a distance substantially remote from transmitter 22. Assembly 35 has tenninals 36 and 37 connected respectively from

terminals

31 and 32.

A load resistor 38 is connected between

junctions

39 and 40. A lead 41 connects junction 39 to counter 24. A capacitor 42 is connected from junction 40 to counter 24. Counter 24 may be an entirely conventional binary counter. Indicator 25 may include simply one lamp for each flip-flop or stage of counter 24 and be calibrated in total volume flow. Any other conventional indicator may also be employed for indicator 25. A DC. source of potential 43 is connected from terminal 36 to junction 39, the positive pole of source 43 being connected to terminal 36.

As shown in FIG. 2, transmitter 22 includes a light chopper 44 having a hub 45 fixed to a disc 46. Rotor shaft 29 is connected relative to hub 45 to rotate disc 46 and hub 45 about the axis thereof. Disc 46 has slots 47 which extend completely therethrough. A light emitting diode 48 shines light through slots 47. A phototransistor 49 produces output pulses at a rate equal to the rate at which slots 47 pass between diode 48 and phototransistor 49.

Pulse transmitter 22 also includes an output circuit 50 which is connected from diode 48 and phototransistor 49 to

terminals

31 and 32.

A more detailed vertical sectional view through pulse transmitter 22 is shown in FIG. 3 including a receptacle-shaped housing 51 having a cover 52 secured thereto by cap screws 53.

Pulse transmitter 22 has an input shaft 54 which is keyed at 55 to fluid motor output shaft 29. Pulse transmitter 22 has an output shaft 56 which is keyed at 57 to an input shaft 58 of mechanical counter-indicator 23.

Input shaft 54 is maintained in a substantially rotatable angular, but fixed axial, position by a snap ring 59 that fits in a groove in shaft 54, not shown, and bears against the left-hand surface 60 of housing 51. A bearing 61 is press fit through an accommodating bore 62 in housing 51, shaft 54 being rotatable in bearing61.

Washers

63 and 64 are loosely fitted on shaft 54 on opposite sides of a gear wheel 65. Gear wheel 65 is fixed relative to shaft 54 by a set screw 66. Bearings 67 and 68 are press fit in cover 52. Input shaft 54' is also rotatable in bearing 67. Output shaft 56 is rotatable in bearing 68. A gear 69 is keyed to shaft 54 at 70. A spur gear 71 is similarly keyed at 72 to output shaft 56, output shaft 56 being slidable through a bore 73 in spur gear 71 in assembly. Output shaft 56 has a flange 74 on the left end thereof integral therewith which has a diameter larger than bore 73. Flange 74 holds gear 71 on output shaft 56. Substantial axial movement of output shaft 56 is prevented by a snap ring 75 which fits in an annular groove of output shaft 56, not shown. The groove in input shaft 54 for snap ring 59 is thus likewise annular. The use of the snap rings 59 and 75 to prevent substantial axial movements of

shafts

54 and 56, respectively, by themselves, is, of course, entirely conventional.

In accordance with the foregoing, the rotation of input shaft 54 not only rotates gear wheel 65, but it also rotates shaft 58 of indicator 23 because the

gears

69 and 71 mesh.

Rotation of gear wheel 65 causes rotation of a pinion 76 because of the driving connection therebetween of a rubber belt 77. Belt 77 is thus flexible, and may be somewhat elastic or resilient, if desired. Belt 77 has ribs 78 which fit in

notches

79 and 80, respectively, in gear wheel 65 and pinion 76, as shown in FIG. 4. Pinion 76 is fixed to a stub shaft 81 by a set screw 82', shown in FIG. 3. Stub shaft 81 is maintained at a substantially fixed axial, but rotatable angular position on a somewhat stiff, but also somewhat flexible, printed circuit board 82. Printed circuit board 82 may be made of any conventional printed circuit board material such as, for example, an insulating material. All of the circuit components shown in FIGS. 10 and 11 may be mounted thereon, although they, for the most part, have, for clarity, been omitted from FIGS. 3, 4, 5, 6, 7 and 8.

In FIG. 3, hub 45 is fixed to stub shaft 81 by a set screw 83. A ferrule 84 has a hex head 85 and an externally threaded shank 86 which projects through a hole 87 in. printed circuit board 82. A hex head nut 88 is threaded to shank 86 and, upon tightening, holds both ferrule 84 and nut 88 in fixed positions relative to board 82.

Ball bearings

89 and 90 are respectively mounted at the right and left ends and inside the hollow cylindrical interior 91 of ferrule 84.

Shaft 81 is maintained in a substantially fixed axial, but rotatable, angular position relative to board 82 by snap rings 92 and 93, as before.

Terminals

31 and 32 are fixed through a disc-shaped insulator 94 which, in turn, is fixed in a hole 95 that ex tends through a wall 96 of housing 51.

Printed circuit board 82 is fixed relative to housing 51 by cap screws 97 that are slidable therethrough but which are threaded into respective bosses 98 inside housing 51, as shown in both FIGS. 3 and 5.

An assembly of diode 48, phototransistor 49 and other structures is indicated at 99 in FIG. 5. An enlarged perspective view of assembly 99 is also shown in FIG. 6, including mounting

blocks

100, 101 and 102 which are fixed relative to printed circuit board 82. If

desired, block 102 may be made of an insulating mate-- rial. If desired, block 101 may be drilled and milled or otherwise fabricated. Block 101 is employed as a collimator. It is not critical that block 101 be made of any certain material or treated in any certain way. However, block 101 is preferably made of 303 stainless steel and is, after fabrication, immersed in a 20 percent concentrated solution of sulfuric acid for two minutes so that its color will turn to brown or black so that it will not reflect light which emanates from the conventional epoxy lens 103 of the conventional light emitting diode 48, shown in FIG. 7.

Block is fixed relative to board 82 by two cap screws 104, only one of which is shown in FIG. 7.

Blocks

101 and 102 are fixed relative to block 100 by two cap screws and 106, shown in both FIGS. 6 and 7.

The axes of both screws 104 may, if desired, be identical with those of the

respective cap screws

105 and 106. Cap screws 104 are slidable through corresponding bores 107 in printed circuit board 82 and threaded into the lower end of block 100. Cap screws 105 and 106 are slidable through-bores 108 and 109 in

blocks

102 and 101, respectively, and threaded into block 100. A conductive layer 110 between

blocks

101 and 102 may be bonded to block 102. Similarly, layer 110 has two holes 111 therethrough through which cap screws 105 and 106 are slidable in assembly.

Layer 1 acts as one conductive lead from diode 48 because it contacts the case thereof. Electrical continuity may be provided from layer 110 to printed circuit board 82 via blocks 101 and 100. For example, both blocks 101 and 100 may be made of a conductive metal.

Diode. 48 is conductively bonded to layer 110 at 112 by an electrically conductive, i.e., silver filled, epoxy. Any suitable bonding agent may be employed. One such suitable bonding agent may be epoxy 302] manufactured by Epoxy Products Co., New Haven, Connecticut. This two component system may have a volume resistivity of 0.003 ohm-centimeter. Another such bonding agent may be EPO-TEK 4l0-E made by Epoxy Technology, Inc., Watertown, Massachusetts. This two component system may have a volume resistivity of 0.0001 to 0.0005 ohm-centimeter.

The bonding agent 112, by conductively bonding the metal case of diode 48 to layer 110, makes it possible to use this as one electrical lead therefrom. The other lead from the diode 48 may be conductively bonded to stem 1 14 of diode 48. That portion of the structure of diode 48 shown in FIG. 7 may be metal with the exception of the epoxy lens 103. Any conventional light emitting diode may be employed for the diode 48. Thus, the following will be given merely as an example. The diode 48 may be a light emitting diode of the gallium arsenide type; 9,300 Angstroms emission peak; D.C. forward voltage drop at 15 milliamperes, 0.8 volts maximum; radiant power use, l.6 milliwatt; radiant power useper ampere, 32 microwatts/ampere typical; peak forward current, l.5 amperes; average forward current, 50 milliamperes; peak inverse current, 2 volts;v storage temperature, 65 to 100 C.; operating temperature, 65 to 75 C.; during soldering (case and stem) for 5 seconds, 130 C. This light emitting diode is sold by Part No. 40736R by RCA, Electronic Components Division, Harrison, New Jersey.

If desired, before bonding at 1 l2, shank 115 of diode 48 may be press fit in ribs 116 in a hole 117 that extends completely through block 102.

Block 101 has a hole 118 which lies in registration with hole 117, and a slot 119 which extends generally through the diameter of hole 1 18. See both FIGS. 6 and 7.

Most of the relative dimensions in FIGS. 3-9, inclusive, may be considered to scale. However, the propertions of the parts are by no means critical.

As shown in FIG. 7, slot 119 is longer than the slots 47. However, in FIG. 8, it is also shown that slot 119 has a width which is equal to the width of each of the slots 47 as indicated at 120.

In FIG. 7, phototransistor 49 has a cylindrical portion 121 which is supported in a bore 122 through a portion of block 100. An insulating film 123 is shrunk on the portion 121 and insulates the metal case of phototransistor 49 from block 100. Phototransistor 49 is-supported in the position shown by solder joints between electrode leads 49 and conductors fixed to board 82, not shown.

In the following, some dimensions will be given regarding disc 46 and slots 47 in FIG. 9. None of. these dimensions are critical.

Disc 46 may be made of 316 stainless steel, if desired. However, this material is not critical. Disc 46 may be 8 mils, thick. Each slot 47 may have a center line such as center line 124, shown in FIG. 9, which passes through the axis of hub 45. The pair of sides of each slot may thus be parallel to the said center line thereof. Each slot may have a width of '10 mils. The semicircular portion of each slot may then be a full radius of 5 mils at each of the two opposite ends of each slot. Each slot 47 may be identical to each of the other slots, if desired. Center line 124 may, for example, intersect the lower arc of a slot 47 at a point 125 which lies a distance from the axis of hub 45 equal to l.0465 inch. Center line 124 may intersect the upper end of its corresponding slot at a point 126. Point 126 may thus lie at distance from the axis of hub 45 equal to 1.156 inch. The outside diameter of disc 46 may be equal to 2.375 inches, if desired.

The angle, A, shown in FIG. 9, is the angle between the center lines of two immediately adjacent slots 47. This angle is l.44. This is true because the slots 47 are equally spaced around the axis of hub 45 and there are 250 slots. Note will be taken that 360 divided by 250 slots is equal to l.44" per slot.

In accordance with the foregoing, the dimension Al in FIG. 9 may be 109.5 mils. The dimension A2 in FIG. 9 is 10 mils.

As is evident from the drawings, the surfaces defining the slots 47 are all normal to the parallel circular surfaces of disc 46.

Output circuit 50 is again shown in FIG. 10 including light emitting diode 48 and phototransistor 49. Also shown are

terminals

31 and 32 having

leads

33 and 34 connected thereto, respectively.

As shown inFlG. 10, diode 48 has an anode 127 and a cathode 128.

Phototransistor 49 has a collector 129 and an emitter 130.

Various junctions are illustrated in FIG. 10 at 131, 132, 133, 134, 135, 136, 137, 138, 139 and 140.

A voltage regulator 141 is connected from leads 33 and 34 to

junctions

133 and 138. Lead 33 may be described as a voltage regulator input lead. Voltage regulator 141 includes

transistors

142 and 143. Transistor 142 has a collector 144, an emitter 145 and a base 146. A lead 147 connects emitter 145 to junction 133 and to diode anode 127. Lead 147 may thus be called the voltage regulator output lead.

Lead 34 has

portions

148, 149, and 151. Lead 34 may thus be described as the common lead. Portion 148 connects terminal 32 to junction 140. Portion 149 is connected between

junctions

139 and 140. Portion 150 is connected between

junctions

138 and 139. Portion 151 is connected between

junctions

137 and 138.

In voltage regulator 141, transistor 143 similarly has a collector 152, an emitter 153 and a base 154. A current regulating diode is illustrated at 155. Diode 155 is connected between junction 131 and a junction 156. Junction 156 is connected to a junction 157 via a lead 158.

Diode 155 may be of a type shown in FIG. 11 including a field effect transistor 159 having a source 160, a drain 161 and a gate 162, gate l62'being connected to source 160 at a junction 163.

In the circuit of FIG. 10, source 160 is connected to junction 156, and drain l61 is connected to junction Lead 33 connects terminal 31 with junction 131. A lead 164 connects

junctions

131 and 132, both of the voltage regulator transistor collectors being connected to junction 132. Transistor base 154 is connected to junction 157. Transistor collector 153 is connected to transistor base 146.

A zener diode 165 is connected between

junctions

156 and 140, and poled in a direction to be back biased by a voltage at junction 156 positive with respect to that at junction 140.

A capacitor 166 is connected between

junctions

157 and 139.

The collector 129 of phototransistor 49 is connected to junction 133. Phototransistor emitter 130 is connected to junction 136. A resistor 167, a diode 168 and a diode 169 are connected in series in succession in that order from junction 136 to junction 138.

The circuit of FIG. 10 also includes transistors 170 and 171. Transistor 170 has a collector 172, an emitter 173 and a base 174. Transistor 171 has a collector 175, an emitter 176 and a base 177.

Base 174 is connected to junction 136. Both

collectors

172 and 175 are connected to junction 135. Emitter 173 is connected to base 177. Emitter 176 is connected to junction 137. A resistor 178 is connected between

junctions

134 and 135. A resistor 179 is connected between

junctions

134 and 137.

Any conventional voltage regulator may be substituted for regulator 141.

Diodes

168 and 169 provide temperature compensation for transistors 170 and 171. Resistor 179 determines the threshold current of light emitting diode 48. For example, transistors 170 and 171 may be cut off if one of the slots 47 is not in alignment with slot 119 in FIG. 7. In this case, effectively no current flows through resistor 178.

When light from diode 48 illuminates phototransistor 49 through a slot 47, transistors 170 and 171 may go to saturation, and the full output voltage of voltage regulator 141 may be impressed across diode 48 and resistor 178. The resistor 178, in this case, then allows additional current to flow through light emitting diode 48. The light output of diode 48 then increases. It is, therefore, a'regenerativeaction. That is, as the illumination of phototransistor 49 increases, the light output of light emitting diode 48 also increases.

Resistor 167 is required to place junction 136 at a potential which is variable with the resistance of phototransistor 49. Typically, phototransistor 49 may have a resistance which varies from 100,000 ohms to 1 megohm. Its resistance is lowest when the illumination thereof is greatest, and vice versa.

As explained previously, the regenerative action provides hysteresis. That is, disc 46, after it has been rotated to a position in which the light output of light emitting diode 48 is a maximum, disc 46 may be rotated through a small angle in the reverse direction without generating a false pulse.

The arcuate distance between the centers of two immediately adjacent slots 47 is about 27.6 mils. In accordance with the present invention, at this mean radius of 1.10125 inch, disc 46 can move in the said reverse direction between about 2.5 and 3.0 mils, and no false output pulse will be generated in the current in leads 33 and 34 when connected as shown in FIG. 1. The reverse is also true. That is, it does not matter whether disc 46 is first advanced to maximum illumination or first advanced to cut off.

The present invention is by no means limited to the specific circuit shown in FIG. 10. Any means for controlling the current through diode 48 or any other light source will suffice in response to the change in resistance of phototransistor 49 or any other photoelectric device due to the illumination thereof.

The components of the circuit of. FIG. 10 may be as follows:

Capacitor 166 0.033 microiarad OPERATION In the operation of the present invention, if the disc 46 is rotated, for example, at a constant speed by fluid motor 21, the current through resistor 38 in FIG. 1 will be a level shifted square wave having a peak value of 16 milliamperes and a minimum value of 8 milliamperes. This current is produced as follows.

First assume that light emitting diode 48 is between disc slots 47. In this case, the current through light emitting diode 48 will be about 8 milliamperes. As soon as a slot 47 moves into partial registration with block slot 119, diode 48 will at least partially illuminate phototransistor 49. The resistance of phototransistor 49 will then begin to drop. This will cause the potential of junction 136 to rise. In turn, this will cause the potentials of both of the transistor bases 174 and 177 to rise. This will permit additional current flow through resistor 178 and through diode 48. As a result, the light output of diode 48 will thus increase and illuminate phototransistor 49 still further even though angular velocity of disc 46 maybe very slow. Thus, the transistors and 171 provide a regenerative feedback of current through diode 48, and the circuit of FIG. 10 acts as a snap action switch, more or less. This snap action makes .the leading and trailing edges of the current pulses through resistor 38 in FIG. 1 extremely square. Moreover, the regenerative feedback provides the aforesaid hysteresis to prevent false current pulse outputs of the circuit of FIG. 10. Such prior art difficulties are not attendant upon the use of the present invention. These difficulties occurred because in the environment of a fluid motor, such as fluid motor 21, it is very difficult to prevent vibration from moving disc 46. However, such vibration produced false pulse outputs in the prior art. In the present invention, the gain of the transistors 170 and 171 may be relatively high. However, by the use of the regenerative feedback, hysteresis is inserted. The present invention thus enjoys the best of both worlds. That is, it is possible to use high gain for exceptionally good sensitivity. Yet, the vibration and false pulse problems have been solved at the same time.

It is also a feature of the invention that the rubber belt 77 provides a positive drive because it has the ribs 78, yet, by being either flexible and/or'resilient, it provides a certain amount of isolation of the fluid motor 21 from the disc 46 to prevent transmission of unwanted vibrations from the motor 21 to the disc 46.

The voltage-current characteristic of the light emitting diode 48 is not particularly linear. On the other hand, it is not particularly nonlinear. At any rate, it is of little consequence in the operation of the circuit. Light emitting diode 48 has, for example, a fairly linear voltage-current characteristic when operated within a region of about 1.15 to 1.20 volts. This may, in some cases, correspond to a current span of between about 5.0 and 10.0 mils.

DEFINITIONS The word indicate, in any of its forms, is hereby defined for use herein and in the claims to mean that a signal is produced in accordance with some function of some variable. In other words, the word indicate" may or may not include producing an indication visible to the human eye. It may, as well, refer to a condition where only a signal is produced Note will be taken that pulse transmitter 22 may be employed for any purpose and for many purposes. Moreover, it may be employed with or without fluid motor 21. Pulse transmitter 22 may also be employed with a synchronous motor or otherwise or without any motor. For example, it may be employed to produce a pulse indication of the position of a device rather than both the position and angular velocity thereof.

Pulse transmitter 22 may also be employed in a position servo, or in a process control system, if desired.

The resistance of light emitting diode 48 may be 230 ohms, but it is by no means limited to this resistance.

Although, in the explanation of the operation of the present invention, a constant speed for disc 46 was referred to, it is to be understood that the system of the present invention is by no means limited to the operation of disc 46 at a constant angular velocity. Moreover, it is the purpose of pulse transmitter 22 to produce output pulses in accordance with the total angle through which disc 46 is rotated. It is not necessary to rotate disc 46 at a constant speed. Further, it is contemplated that the angular velocity of the output shaft 29 of fluid motor 21 will not be constant. Moreover, from time to time, it may be considered to have an angular velocity equal to zero. Typically, disc 46 may rotate at an angular velocity such that current pulses are passed through resistor 38 in FIG. 1 at a rate of about 100 pulses per second.

The word, connection," in any of its forms, is hereby defined for use herein and in the claims to include, but not be limited to, means by which one or more conductive leads or junctions, and/or means by which one or more circuit elements are connected together. In other words, the word, connection, not only may or may not include or be limited to a conductive lead or junction, but this word, connection, may or may not include a circuit element.

If desired, disc 46 may be made by etching the slots 47 therethrough in any conventional manner.

As will be evident from FIG. 7, light emitting diode 48 and phototransistor 49 generally have a common symmetrical axis. This axis then passes through the center of each slot 47 when each slot lies registration with slot 119.

What is claimed is:

1. In a pulse generating system, the combination comprising: a base; a drive means shaft fixed at one end to said base in a substantially stationary axial position relative thereto and a rotatable angular position relative thereto, said drive means shaft having an axis; a first gear wheel fixed relative to said drive means shaft; a stub shaft; said stub shaft having an axis, said stub shaft being rotatably mounted relative to said base in a position such that its axis is parallel to that of said drive means shaft; a mounting member fixed to said base, said stub shaft being mounted on said mounting member, whereby vibration of said stub shaft by said drive means shaft is reduced; a second gear wheel rotatably mounted on said stub shaft at an axial location thereof the same as the axial location of said first gear wheel on said drive means shaft; an endless flexible drive belt extending around both of said gear wheels, said drive belt having equally spaced ribs of substantially the same size on the inside thereof extending in a direction having a component parallel to said axes, each of said gear wheels having equally spaced teeth, a portion of said ribs being disposed between respective pairs of immediately adjacent teeth, an light chopper having apertures therethrough, said chopper being fixed relative to said second gear wheel; a source of light fixed relative to said base in a position to shine light through said chopper apertures; and a photoelectric device fixed relative to said base in a position to receive light from said source after it has passed through said apertures.

2. The invention as defined in claim 1, including a fluid motor connected in a manner to rotate said drive shaft, output means responsive to the output of said photoelectric device to produce an output pulse each time an aperture passes between said light source and said device, and means calibrated in fluid volume connected from said output means to indicate the number of said pulses.

3. The invention as defined in claim 2, wherein each of said gear wheels has a flange on each side thereof to hold said drive belt thereon, said drive belt being made of a rubber-like material, said output means including a circuit on a printed circuit board fixed relative to said base only at spaced and isolated positions thereon, said stub shaft being mounted on said printed circuit board in a position spaced from said isolated positions, said flexible, rubber-like drive belt and said printed circuit board mounting of said stub shaft providing vibration isolation for said light chopper.

4. A pulse transmitter comprising: a base; a stub shaft rotatably mounted relative to said base; an light chopper having apertures therethrough, said chopper being mounted in a fixed axial but rotatable angular position relative to said base, said chopper being rotatable about the axis of said stub shaft, said stub shaft having a fixed axial position relative to said base; means to rotate said light chopper relative to said base; a source of light fixed relative to said base in a position to shine light through said chopper apertures; and a photoelectric device fixed relative to said base in a position to receive light from said source after it has passed through said apertures; and a printed circuit board fixed relative to said base only at spaced and isolated positions thereon, said stub shaft being mounted on said printed circuit board in a position spaced from said isolated positions, said printed circuit board mounting of said stub shaft providing vibration isolation for said light chopper.

5. In a pulse generating system, the combination comprising: a base; a light chopper movably mounted relative to said base, said light chopper having at least one opaque portion defining at least one light transmissive aperture movable therewith; a source of light fixed relative to said base in a position on one side of said light chopper to shine light through said aperture in one position thereof; a photoelectric device fixed relative to said base on the side of said light chopper opposite said one side thereof to receive light from said source that passes through said aperture when said aperture is positioned between said source and said device; first means connected from said device to said source to increase the light output of said source when the resistance of said device decreases, and vice versa, said device resistance decreasing and increasing, respectively, when the illumination thereof by said source through said aperture increases and decreases, second means connected from said photoelectric device to produce a pulse each time said aperture passes between said source and said device, third means to rotate said light chopper, and fourth means to indicate the number of pulses produced; said source of light including a light emitting diode, said first means being adapted to increase the current through said light emitting diode when the resistance of said photoelectric device decreases, and vice versa, said device being a phototransistor; said third means including a fluid motor, said first and second means being incorporated in an output circuit including first and second output terminals, a voltage regulator having first and second input leads connected from said first and second terminals, respectively, said regulator having first and second output leads, a first resistor and first and second diodes connected in succession in that order from the phototransistor emitter to said second output lead, the phototransistor collector being connected to said first output lead, first and second transistors each having a collector, an emitter and a base, said first transistor base being connected to said phototransistor emitter, said first and second transistor collectors being connected together, said first transistor emitter being connected to said second transistor base, said second transistor emitter being connected to said second output lead, said light emitting diode having an anode connected to said first output lead, a second resistor connected from said second transistor collector to a first junction, said light emitting diode having a cathode connected to said first junction, and a third resistor connected between said first junction and said second output lead.

6. The invention as defined in claim 5, wherein said voltage regulator includes third and fourth transistors each having a collector, an emitter and a base, said voltage regulator also including a current regulating diode, a zener diode and a capacitor, said third transistor collector and emitter being connected to said first input and output leads, respectively, said fourth transistor collector being connected to said first input lead, said fourth transistor emitter being connected to said third transistor base, said current regulating diode including a field effect transistor having a source, a drain and a gate, said fourth transistor base and said source and gate being connected to a second junction, said drain being connected to said first input lead, said second leads being connected together, said capacitor and said zener diode being connected in parallel from said second junction to said second leads.

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