CA1117598A - Bridge circuit - Google Patents
Bridge circuitInfo
- Publication number
- CA1117598A CA1117598A CA000312167A CA312167A CA1117598A CA 1117598 A CA1117598 A CA 1117598A CA 000312167 A CA000312167 A CA 000312167A CA 312167 A CA312167 A CA 312167A CA 1117598 A CA1117598 A CA 1117598A
- Authority
- CA
- Canada
- Prior art keywords
- junction
- resistor
- ada
- output
- corner
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/225—Measuring circuits therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R17/00—Measuring arrangements involving comparison with a reference value, e.g. bridge
- G01R17/10—AC or DC measuring bridges
Abstract
E. Romo 2 BRIDGE CIRCUIT
ABSTRACT OF THE DISCLOSURE
A circuit including a strain gage bridge to produce an electrical signal from a mechanical deflection. The circuit has a differential amplifier to supply a constant current to the bridge. Linearization and accuracy are obtained through a feedback connection to the differential amplifier.
The constant current feature, a temperature compensation feature and a common mode rejection feature are employed to improve accuracy. A constant current source for a bridge is new in the art.
ABSTRACT OF THE DISCLOSURE
A circuit including a strain gage bridge to produce an electrical signal from a mechanical deflection. The circuit has a differential amplifier to supply a constant current to the bridge. Linearization and accuracy are obtained through a feedback connection to the differential amplifier.
The constant current feature, a temperature compensation feature and a common mode rejection feature are employed to improve accuracy. A constant current source for a bridge is new in the art.
Description
E. A. P~omo 2 BACKGROUND OF THE INVENTION
This invention rela~es to a bridge having an element connected therein, the re~istance o~ which changes with some variable, and more particularly to a strain gage b~idge or the like.
In the past, strain gage bridge circuits have suf~ered from inaccuracies due to asymmetrical strain gages, amplifier distortion, and other non-linearities.
PRIOR ART STATEMENT
Th~ voltage regulator disclosed in this application may be similar to or identical to voltage regulator 127 disclosed in U. S. Patent No. 3,725,665, issued April 3, 1973.
The utiLity o~ the invention of this application may include but not be limited to a combination where the circuit of the invention is substituted for that shown in Fig. 4 of U. S. Patent No. 3,722,264 issued March 27, 1973.
Regarding U. S. Patent No~ 3,532,869 issued October 6, 1970, see the abstract.
Ragarding U. 5. Patent No. 3,161,821 issued December 15, 201964, note amplifiers 11, lL', 15, 15'~, 34 and 42.
Regardlng U. S. Patent No. 3,434,343 issued March 25, 196g, note column 3, line 46 et seq.
Regarding U. S. Patent No. 3,518,886 issued July 7, 1970, see circuit 19 in Flg. 1.
25Regarding V. S. Patent No. 3,568,044 issued March 2, L971, ~-e resis:br 42.
' .
This invention rela~es to a bridge having an element connected therein, the re~istance o~ which changes with some variable, and more particularly to a strain gage b~idge or the like.
In the past, strain gage bridge circuits have suf~ered from inaccuracies due to asymmetrical strain gages, amplifier distortion, and other non-linearities.
PRIOR ART STATEMENT
Th~ voltage regulator disclosed in this application may be similar to or identical to voltage regulator 127 disclosed in U. S. Patent No. 3,725,665, issued April 3, 1973.
The utiLity o~ the invention of this application may include but not be limited to a combination where the circuit of the invention is substituted for that shown in Fig. 4 of U. S. Patent No. 3,722,264 issued March 27, 1973.
Regarding U. S. Patent No~ 3,532,869 issued October 6, 1970, see the abstract.
Ragarding U. 5. Patent No. 3,161,821 issued December 15, 201964, note amplifiers 11, lL', 15, 15'~, 34 and 42.
Regardlng U. S. Patent No. 3,434,343 issued March 25, 196g, note column 3, line 46 et seq.
Regarding U. S. Patent No. 3,518,886 issued July 7, 1970, see circuit 19 in Flg. 1.
25Regarding V. S. Patent No. 3,568,044 issued March 2, L971, ~-e resis:br 42.
' .
- 2 - ~
~ E. A. Komo 2 Regarding U S. Patent No. 3,841,150 i.ssued October 15, 1974, see the abstract and resistor 71 in Fig. 3.
Regarding U. S. Patent No. 3,847,017 issued November 12, 1974, see amplifiers A3 and A4.
~egarding U. S. Patent No. 3,967,188 issued June 29, 1976, see the abstract.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a detector circuit comprising: a Wheatstone bridge having first, second, third and fourth corner junctions; a first reference leg connected between said second and third corner junctions; a second reference leg connected between said third and fourth ! corner junctions; a first active leg having a changeable resistance connected between one of two pairs of said corner junctions, one of said pairs being said fourth and first corner junctions, the other of said pairs being said first and second corner junctions; a main differential amplifier having inverting and noninverting inputs, and an output; first means to supply a regulated voltage to said main differential amplifier 20 noninverting input, said main differential amplifier output being cannected to said second corner junction, said fourth corner junction being connected to said main differential amplifier invorting input; second means provi~ing resistance , .
~ E. A. Komo 2 Regarding U S. Patent No. 3,841,150 i.ssued October 15, 1974, see the abstract and resistor 71 in Fig. 3.
Regarding U. S. Patent No. 3,847,017 issued November 12, 1974, see amplifiers A3 and A4.
~egarding U. S. Patent No. 3,967,188 issued June 29, 1976, see the abstract.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a detector circuit comprising: a Wheatstone bridge having first, second, third and fourth corner junctions; a first reference leg connected between said second and third corner junctions; a second reference leg connected between said third and fourth ! corner junctions; a first active leg having a changeable resistance connected between one of two pairs of said corner junctions, one of said pairs being said fourth and first corner junctions, the other of said pairs being said first and second corner junctions; a main differential amplifier having inverting and noninverting inputs, and an output; first means to supply a regulated voltage to said main differential amplifier 20 noninverting input, said main differential amplifier output being cannected to said second corner junction, said fourth corner junction being connected to said main differential amplifier invorting input; second means provi~ing resistance , .
- 3 , . . .
E. A. Rorno 2 connected from saicl fourth corner junction to groun~, the current from the output of said main diEferential amplifier being constant at least at a constant temperature; output means connected from said first and third corner junctions; and utilization means connected from said output means.
BRIEF DESCRIPTION OF THE DRAWING
. _ _ _ _ _ The figure is a schematic diagram of the circuit of the present invention.
- DESCRIPTION OF THE PREFERRED EMBODIMENT
, _ , In the drawing~ a battery is provided at 10 connected to input junctions 11 and 12 through diode 13 and resistor 14, respectively. Diode 13 is poled to be conductive from a positive pole of battery 10 to junction 11.
Battery 10 has a negative pole connected to junction 12 through resistor 14. A voltmeter calibrated in differential pressure is provided at 15 and connected in parallel with resistor 14. The lead between battery 10 and diode 13 may be very long, if desired. The same is true of the lead from resistor 14 to junction 1~.
Junction 12 is connected to ground. An output resistor is provided at 16 connected from a junction 17 to junction 12.
Other junctions are connected through the figure as follows.
~ .
E. A. Romo 2 There is a junction 18, a junction 1~, a junction 20, a junction 21, a junction 22, a junction 23, a junction 24, a junction 25, a junction 26, a junction 27, a junction 28, a junction 29, a junction 30, a junc~ion 31, a junction 32, a junction 33, a junc-tion 34, a junction 35, a junction 36, a junction 37, a junction 38, a junction 39, a junction 40, a junction 41, a junction 42, a junction 43, a junction 44, a junction 4S, a junction 46, a junction 47, a junction 48, a junction 49, a junction 5~ and a junction 51 shawn in the drawing.
The circuitry found in dotted box SZ is a voltage regu-lator which, if desired, may be conventional. Transistors are provided at 53 and 54. Transistor 53 has a collector 55, an emitter 56 and a base 57. Base 57 is connected from junction 18.
Tran istor 54 has a collector 58, an emitter 59 and a base 60.
A zener diode is provided at 61 connected be~ween junctions ~8 and 20. A resistor 62 is provided connected from junction 20 to emitter 56. Collector 55 is connected to junction 21. Junctions 21, 22 and 23 are connected together. A zener diode 63 is con-nected from junction 23 to ground. A resistor 64 is connected from junction 18 to junction 19. Junction 19 is connected to ground. Base 60 is connected from junction 22. A resistor 65 is connected from emitter 59 to junction 19. Collector 58 is connected from junction 18.
Junction 20 is connected from junction 11. Voltage regulator 52 acts as a source of potential for a differential amplifier 66 connected from junction 21 in voltage regulator 52.
,, 7'~ f?, E A. Romo 2 Differential amplifiers are also provided at 67, 68 and 69. A strain gage bridge is provided at 70. Strain gages are provided at 71 and 72. Resistors are pro~ided at 73 and 74. A
potentiometer is provided at 75 having a winding 76 and a wiper 77. The potential of wiper 77 is one corner of the bridge 70.
The other corners are the junctions 24, 27 and 28. A xesistor 78 is connected parallel with winding 76. Auxiliary resistors are provided at 79 and 80. A conventional di~ferential pressure unit is provided at 81 to stress strain gages 71 and 72 so that voltmeter 15 can be calibrated in differential pressure. Th~
differen~ial pressure unit 81 may be of the prior art type de-scribed hereinbefore. The position o~ wiper 77 provides a zero adjustment. The position of wiper 82 of a ~ariable resistor 83 provides a span adjustment.
A temperature compensatiny resistor is provided at 84 connected between terminals 85 and 86. Terminals 85 and 86 are, in turn, connected to junctions 32 and 33, respectively. Depend-ing upon the algebraic sign of the temperature correction needed, resistor 8~ is connected as shown or between terminals 87 and 88 connected to junctions 34 and 35. A resistor 89 is connected between junctions 32 and 33. -A resistor 90 is connected between junctions 34 and 35. Linearity through feedback is provided at one of the junctions 33 and 36. As shown, the feedback is pro-vided through a resistor 91 and a jumper 92 between terminals 93 and 94 to junction 36.
E. A. Romo 2 In iks other position, jumper 9Z is connected from ter-minal 93 to a terminal 95. Resistor 91 is connect~d from junc-tion 51. ~unctions 27 and 30 are connected together. A resistor 96 is connected between junctions 30 and 34. The inve~ted input of amplifier 67 is connected from junction 30. A resistor 97 is connected between junctions 31 and 32. A resistor 98 is connected between junctions 23 and 31. The non-inverting input of amplifier 67 is connected from junction 31.
With no change in temperature, or with a change in tem-perature, the amplifier 67 keeps the current at the output thereof and from junction 27 to junction 30 constant. The gain of ampli-fier 67, as is conventional, may be anywhere from 100,000 or less to 500,000 or more. This means that junction 30 is always driven to the potential of junction 31.
If strain gages 71 and 72 are not symmetrical, the con-stant current drive of amplifier 67 still maintains the output thereof accurate. The circuit connected from wiper 77 and junc~
tion 28 is, for the most part, a common mode rejection circuit which also improves accuracy. A resistor 99 is connectad from wiper 77 to junction 37. A capacitor 100 is connected between junctions 29 and 37. Junctions 28 and 29 are connected to the noninverting input of amplifier 66. Amplifier 68 has a feedback resistor 101. Amplifier 66 has a feedback resistor 102. Junc-tion 45 is connected from the output of amplifier 66. Resistor 102 is connected from junction 44 to the inverting input of ~ E~ A. Romo 2 amplifier 66. Junction3 4~ and 45 are connected together.
~unctions 43 and 44 are connec~ed ~ogether. Variable resistor 83 is co~mected ~rom junction 43 to junction 42. Terminals 103, 104, 105 and 106 are connected respec~lvely frorn junctions 42, 41, 40 and 39, so that re~istors 107 and/or 108 and/or lOg may be shorted or opened.
Feedback resistor 101 is connected between junctions 38 and 47. The output o~ ampli~ier 68 is connected to junction 47.
The noninverting input of amplifier 68 is connected from junc-tion 37. The inverting input of an amplifier 68 is connected from junction 38. Junctions 38 and 39 are connected together.
A resistor 110 is connected from junction 45 to junction 46.
A resistor 111 is connected from junction 47 to junction 4a. A
resistor 112 is connected from junction 46 to junction 51. Junc-tions 17 and 51 are connected together. A resistor 113 is con-nected from junction 48 to ground. The inverting and noninvert-ing inputs of amplifier 69 are respectively connected from ~unc-tions 46 and 48.
A resistor 114 is connected from the output of amplifier 69 to a base 115 of a transistor 116 having a collector 117 and an emitter 118. Colleckor 117 is connected to junction 50.
~unctions 11 and 50 are connected together. Another transistor is provided at 118' having a collector 119, an emitter 120 and a base 121. Emitter 118 i5 connected to junction 49. Base 121 is connected ~rom ju~ction 49. Collector 119 is connected ~rom " ~ 3 E, A. ~omo 2 junction 50. A resistor 122 i.5 co~nected ~rom collector 120 to junction 17. A resistor 4g' is connected between junc'cions 49 and 51. Resistors 33' and 34' have a resistance normally sub-stantially less than that of resistors 97 and 96, respec~ively.
Some circuit component values are listed in the ~ollow-ing:
Resistors 14 10 ohms 33' 200 o~ns 34' 200 ohms 49' 4,700 ohms 62 1,500 ohms 64 22 megohms 65 20,000 ohms . 73 7,500 ohms 74 7,500 ohms 78 10 ohms 96 3,200 ohms 97 10,000 ohms 98 10,000 ohms 99 2,200 ohms 10175,000 ohms 10275,000 ohms 107 5,000 ohms 108 5,000 ohms i 'h3 E. A. Romo 2 Resistors (Cont ' d) 10~) ' 5, OOO ohms 110 75,000 ~hms 111 75, O~O o~ms 112 75, OOO o~ms 113 75,000 o~ms 114 22û ohms 12Z 22 ohms W~
76 lOO ohms Al)S ~ rm .~ - ..
~ .
- ~ .
.
.
~ ' ; ` :
- .l O
E. A. Rorno 2 connected from saicl fourth corner junction to groun~, the current from the output of said main diEferential amplifier being constant at least at a constant temperature; output means connected from said first and third corner junctions; and utilization means connected from said output means.
BRIEF DESCRIPTION OF THE DRAWING
. _ _ _ _ _ The figure is a schematic diagram of the circuit of the present invention.
- DESCRIPTION OF THE PREFERRED EMBODIMENT
, _ , In the drawing~ a battery is provided at 10 connected to input junctions 11 and 12 through diode 13 and resistor 14, respectively. Diode 13 is poled to be conductive from a positive pole of battery 10 to junction 11.
Battery 10 has a negative pole connected to junction 12 through resistor 14. A voltmeter calibrated in differential pressure is provided at 15 and connected in parallel with resistor 14. The lead between battery 10 and diode 13 may be very long, if desired. The same is true of the lead from resistor 14 to junction 1~.
Junction 12 is connected to ground. An output resistor is provided at 16 connected from a junction 17 to junction 12.
Other junctions are connected through the figure as follows.
~ .
E. A. Romo 2 There is a junction 18, a junction 1~, a junction 20, a junction 21, a junction 22, a junction 23, a junction 24, a junction 25, a junction 26, a junction 27, a junction 28, a junction 29, a junction 30, a junc~ion 31, a junction 32, a junction 33, a junc-tion 34, a junction 35, a junction 36, a junction 37, a junction 38, a junction 39, a junction 40, a junction 41, a junction 42, a junction 43, a junction 44, a junction 4S, a junction 46, a junction 47, a junction 48, a junction 49, a junction 5~ and a junction 51 shawn in the drawing.
The circuitry found in dotted box SZ is a voltage regu-lator which, if desired, may be conventional. Transistors are provided at 53 and 54. Transistor 53 has a collector 55, an emitter 56 and a base 57. Base 57 is connected from junction 18.
Tran istor 54 has a collector 58, an emitter 59 and a base 60.
A zener diode is provided at 61 connected be~ween junctions ~8 and 20. A resistor 62 is provided connected from junction 20 to emitter 56. Collector 55 is connected to junction 21. Junctions 21, 22 and 23 are connected together. A zener diode 63 is con-nected from junction 23 to ground. A resistor 64 is connected from junction 18 to junction 19. Junction 19 is connected to ground. Base 60 is connected from junction 22. A resistor 65 is connected from emitter 59 to junction 19. Collector 58 is connected from junction 18.
Junction 20 is connected from junction 11. Voltage regulator 52 acts as a source of potential for a differential amplifier 66 connected from junction 21 in voltage regulator 52.
,, 7'~ f?, E A. Romo 2 Differential amplifiers are also provided at 67, 68 and 69. A strain gage bridge is provided at 70. Strain gages are provided at 71 and 72. Resistors are pro~ided at 73 and 74. A
potentiometer is provided at 75 having a winding 76 and a wiper 77. The potential of wiper 77 is one corner of the bridge 70.
The other corners are the junctions 24, 27 and 28. A xesistor 78 is connected parallel with winding 76. Auxiliary resistors are provided at 79 and 80. A conventional di~ferential pressure unit is provided at 81 to stress strain gages 71 and 72 so that voltmeter 15 can be calibrated in differential pressure. Th~
differen~ial pressure unit 81 may be of the prior art type de-scribed hereinbefore. The position o~ wiper 77 provides a zero adjustment. The position of wiper 82 of a ~ariable resistor 83 provides a span adjustment.
A temperature compensatiny resistor is provided at 84 connected between terminals 85 and 86. Terminals 85 and 86 are, in turn, connected to junctions 32 and 33, respectively. Depend-ing upon the algebraic sign of the temperature correction needed, resistor 8~ is connected as shown or between terminals 87 and 88 connected to junctions 34 and 35. A resistor 89 is connected between junctions 32 and 33. -A resistor 90 is connected between junctions 34 and 35. Linearity through feedback is provided at one of the junctions 33 and 36. As shown, the feedback is pro-vided through a resistor 91 and a jumper 92 between terminals 93 and 94 to junction 36.
E. A. Romo 2 In iks other position, jumper 9Z is connected from ter-minal 93 to a terminal 95. Resistor 91 is connect~d from junc-tion 51. ~unctions 27 and 30 are connected together. A resistor 96 is connected between junctions 30 and 34. The inve~ted input of amplifier 67 is connected from junction 30. A resistor 97 is connected between junctions 31 and 32. A resistor 98 is connected between junctions 23 and 31. The non-inverting input of amplifier 67 is connected from junction 31.
With no change in temperature, or with a change in tem-perature, the amplifier 67 keeps the current at the output thereof and from junction 27 to junction 30 constant. The gain of ampli-fier 67, as is conventional, may be anywhere from 100,000 or less to 500,000 or more. This means that junction 30 is always driven to the potential of junction 31.
If strain gages 71 and 72 are not symmetrical, the con-stant current drive of amplifier 67 still maintains the output thereof accurate. The circuit connected from wiper 77 and junc~
tion 28 is, for the most part, a common mode rejection circuit which also improves accuracy. A resistor 99 is connectad from wiper 77 to junction 37. A capacitor 100 is connected between junctions 29 and 37. Junctions 28 and 29 are connected to the noninverting input of amplifier 66. Amplifier 68 has a feedback resistor 101. Amplifier 66 has a feedback resistor 102. Junc-tion 45 is connected from the output of amplifier 66. Resistor 102 is connected from junction 44 to the inverting input of ~ E~ A. Romo 2 amplifier 66. Junction3 4~ and 45 are connected together.
~unctions 43 and 44 are connec~ed ~ogether. Variable resistor 83 is co~mected ~rom junction 43 to junction 42. Terminals 103, 104, 105 and 106 are connected respec~lvely frorn junctions 42, 41, 40 and 39, so that re~istors 107 and/or 108 and/or lOg may be shorted or opened.
Feedback resistor 101 is connected between junctions 38 and 47. The output o~ ampli~ier 68 is connected to junction 47.
The noninverting input of amplifier 68 is connected from junc-tion 37. The inverting input of an amplifier 68 is connected from junction 38. Junctions 38 and 39 are connected together.
A resistor 110 is connected from junction 45 to junction 46.
A resistor 111 is connected from junction 47 to junction 4a. A
resistor 112 is connected from junction 46 to junction 51. Junc-tions 17 and 51 are connected together. A resistor 113 is con-nected from junction 48 to ground. The inverting and noninvert-ing inputs of amplifier 69 are respectively connected from ~unc-tions 46 and 48.
A resistor 114 is connected from the output of amplifier 69 to a base 115 of a transistor 116 having a collector 117 and an emitter 118. Colleckor 117 is connected to junction 50.
~unctions 11 and 50 are connected together. Another transistor is provided at 118' having a collector 119, an emitter 120 and a base 121. Emitter 118 i5 connected to junction 49. Base 121 is connected ~rom ju~ction 49. Collector 119 is connected ~rom " ~ 3 E, A. ~omo 2 junction 50. A resistor 122 i.5 co~nected ~rom collector 120 to junction 17. A resistor 4g' is connected between junc'cions 49 and 51. Resistors 33' and 34' have a resistance normally sub-stantially less than that of resistors 97 and 96, respec~ively.
Some circuit component values are listed in the ~ollow-ing:
Resistors 14 10 ohms 33' 200 o~ns 34' 200 ohms 49' 4,700 ohms 62 1,500 ohms 64 22 megohms 65 20,000 ohms . 73 7,500 ohms 74 7,500 ohms 78 10 ohms 96 3,200 ohms 97 10,000 ohms 98 10,000 ohms 99 2,200 ohms 10175,000 ohms 10275,000 ohms 107 5,000 ohms 108 5,000 ohms i 'h3 E. A. Romo 2 Resistors (Cont ' d) 10~) ' 5, OOO ohms 110 75,000 ~hms 111 75, O~O o~ms 112 75, OOO o~ms 113 75,000 o~ms 114 22û ohms 12Z 22 ohms W~
76 lOO ohms Al)S ~ rm .~ - ..
~ .
- ~ .
.
.
~ ' ; ` :
- .l O
Claims (7)
1. A detector circuit comprising: a Wheatstone bridge having first, second, third and fourth corner junctions; a first reference leg connected between said second and third corner junctions; a second reference leg connected between said third and fourth corner junctions; a first active leg having a changeable resistance connected between one of two pairs of said corner junctions/
one of said pairs being said fourth and first corner junctions, the other of said pairs being said first and second corner junctions; a main differential amplifier having inverting and noninverting inputs, and an output; first means to supply a regulated voltage to said main differential amplifier noninverting input, said main differential amplifier output being connected to said second corner junction, said fourth corner junction being connected to said main differential amplifier inverting input; second means providing resistance connected from said fourth corner junction to ground, the current from the output of said main differential amplifier being constant at least at a constant temperature; output means connected from said first and third corner junctions; and utilization means connected from said output means.
one of said pairs being said fourth and first corner junctions, the other of said pairs being said first and second corner junctions; a main differential amplifier having inverting and noninverting inputs, and an output; first means to supply a regulated voltage to said main differential amplifier noninverting input, said main differential amplifier output being connected to said second corner junction, said fourth corner junction being connected to said main differential amplifier inverting input; second means providing resistance connected from said fourth corner junction to ground, the current from the output of said main differential amplifier being constant at least at a constant temperature; output means connected from said first and third corner junctions; and utilization means connected from said output means.
2. The invention as defined in claim 1, wherein said utilization means includes a meter calibrated in differential pressure.
E. A. Romo 2
E. A. Romo 2
3. The invention as defined in claim 1, wherein a second active leg is provided, each of said first and second active legs including a strain gage, a differential pressure unit connected to stress said first and second active legs so that one is in compression while the other is in tension, and vice versa, said first active leg being connected between said fourth and first corner junctions, said second active leg being connected between said first and second corner junctions.
4. The invention as defined in claim 1, wherein said first and second means include at least first and second re-sistors, respectively, said first resistor being connected from said main differential amplifier noninverting input to ground, said second resistor being connected from said fourth corner junction to ground.
5. The invention as defined in claim 4, wherein third and fourth resistors are provided and are connected in series with said first and second resistors, respectively, from one end thereof to ground, and a feedback resistor connected from said output means to the ungrounded side of one of said third and fourth resistors, said first, second, third and fourth re-sistors having resistances R1 R2, R3 and R4, respectively, where R3 ? R4, R1 >> R3, R2 >> R4, and R1 and R2 are the same order of magnitude.
E. A. Romo 2
E. A. Romo 2
6. The invention as defined in claim 1, wherein one of said first and second means are temperature sensitive.
7. The invention as defined in claim 1, wherein said output means includes a first auxiliary differential amplifier (ADA), and second and third auxiliary differential amplifiers (ADAs), each of the said three of which has a noninverting input, an inverting input, and an output, said first ADA noninverting input being connected from said third corner junction, a first resistor connected from said first corner junction to said second ADA noninverting input, a capacitor connected between the non-inverting inputs of said first and second ADAs, second and third resistors connected respectively from the outputs of said first and second ADAs to the respective inverting inputs of said first and second ADAs, a variable resistor connected from the output of said first ADA to the inverting input of said second ADA, a fourth resistor connected from said first ADA output to said third ADA inverting input, a fifth resistor connected from the output of said second ADA to the noninverting input of said third ADA, a sixth resistor connected from the noninverting input of said third ADA to ground, a Darlington pair including first and second transistors each having a collector, an emitter and a base, a seventh resistor connected from the output of said third ADA to said first transistor base, the first transistor emitter being connected to said second transistor base, both of the collectors being connected together, eighth and ninth resistors connected in that order from the second transistor emitter to ground, tenth E. A. Romo 2 and eleventh resistors connected respectively from said first transistor emitter and from the inverting input of said third ADA to the ungrounded side of said ninth resistor, a source of D.C. potential, a twelfth resistor connected from said collec-tors to ground, and a voltmeter calibrated in differential pressure and connected in parallel with said twelfth resistor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US83745277A | 1977-09-28 | 1977-09-28 | |
| US837,452 | 1977-09-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117598A true CA1117598A (en) | 1982-02-02 |
Family
ID=25274484
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000312167A Expired CA1117598A (en) | 1977-09-28 | 1978-09-27 | Bridge circuit |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1117598A (en) |
| DE (1) | DE2841491A1 (en) |
| GB (1) | GB2009947B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS55113904A (en) * | 1979-02-26 | 1980-09-02 | Hitachi Ltd | Method of zero point temperature compensation for strain-electric signal transducer |
| US4444056A (en) * | 1982-05-05 | 1984-04-24 | Itt Corporation | Temperature compensated circuit |
| DE3810456C2 (en) * | 1988-03-26 | 1994-09-01 | Hottinger Messtechnik Baldwin | Method for reducing an error in a transmitter and device therefor |
| US4890497A (en) * | 1988-08-25 | 1990-01-02 | Dwyer Instruments, Inc. | Differential pressure gauge transmitter |
| CN105300269B (en) * | 2015-11-16 | 2019-10-08 | 广东省智能制造研究所 | A kind of wireless accurate strain gauge means and a kind of wireless accurate strain measurement method |
-
1978
- 1978-08-29 GB GB7834907A patent/GB2009947B/en not_active Expired
- 1978-09-23 DE DE19782841491 patent/DE2841491A1/en not_active Ceased
- 1978-09-27 CA CA000312167A patent/CA1117598A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2009947B (en) | 1982-03-24 |
| DE2841491A1 (en) | 1979-04-05 |
| GB2009947A (en) | 1979-06-20 |
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