CA1094847A - Digital readout gauge - Google Patents
Digital readout gaugeInfo
- Publication number
- CA1094847A CA1094847A CA311,464A CA311464A CA1094847A CA 1094847 A CA1094847 A CA 1094847A CA 311464 A CA311464 A CA 311464A CA 1094847 A CA1094847 A CA 1094847A
- Authority
- CA
- Canada
- Prior art keywords
- gauge
- digital readout
- digital
- set forth
- electrical circuit
- 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
- 239000003990 capacitor Substances 0.000 claims description 23
- 239000004020 conductor Substances 0.000 claims description 14
- 239000012530 fluid Substances 0.000 claims description 6
- 239000002184 metal Substances 0.000 claims description 4
- 239000013078 crystal Substances 0.000 abstract description 26
- 238000005259 measurement Methods 0.000 description 3
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L17/00—Devices or apparatus for measuring tyre pressure or the pressure in other inflated bodies
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/08—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of piezoelectric devices, i.e. electric circuits therefor
Abstract
DIGITAL READOUT GAUGE
Abstract of the Disclosure A digital readout gauge is disclosed which, for example, may be a tire pressure gauge which is mounted in a small portable housing. A pressure chamber is formed within the housing with a valve core deflator mounted within the housing to depress the core of a standard tire valve and permit the air pressure within the tire to be introduced- into the chamber. A wall of the chamber is movable with changes of pressure and a piezoelectric crystal is mounted to be stressed in accordance with movement of this wall to develop an analog voltage in accordance with the air pressure. An electrical circuit is contained within the housing and energizable by a battery carried within the housing. A power switch is actuated on by movement of the gauge onto the tire valve to energize the electrical circuit with the analog voltage passed to an analog to digital converter and then to a digital readout display to display the digital value of the air pressure within the tire.
Abstract of the Disclosure A digital readout gauge is disclosed which, for example, may be a tire pressure gauge which is mounted in a small portable housing. A pressure chamber is formed within the housing with a valve core deflator mounted within the housing to depress the core of a standard tire valve and permit the air pressure within the tire to be introduced- into the chamber. A wall of the chamber is movable with changes of pressure and a piezoelectric crystal is mounted to be stressed in accordance with movement of this wall to develop an analog voltage in accordance with the air pressure. An electrical circuit is contained within the housing and energizable by a battery carried within the housing. A power switch is actuated on by movement of the gauge onto the tire valve to energize the electrical circuit with the analog voltage passed to an analog to digital converter and then to a digital readout display to display the digital value of the air pressure within the tire.
Description
1 Background of the Invention Digital gauges have been used in the prior art, for example, a weighing scale with a digital readout and also fluid pressure measurement devices with a digital readout. Several systems have used a load cell to develop a voltage proportional to the weigh~ of an object but many of these devices have been large and cumbersome and quite expensive. Other systems have used pressure transducers or a variable electrode capacitor but all have been relatively large and cumbersome and require excessive electrical energy.
Accordingly the problem to be solved is how to achieve a small compact portable digital readout force gauge which is accurate and yet requires a minimum of electrical energy lnput.
, . .
Summary of the Invention This problem may be solved by a digital readout gauge, comprising, in combination, a housing, a chamber in said housing, wall means in said chamber movable with changes of force on said wall means, means to apply a changeable force on said wall means, an electrical circuit in said housing, a battery in said housing and connected to supply power to said electrical circuit, said electrical circuit including a piezoelectric crystal mounted to be stressed in accordance with movement of said movable wall means, output conductors connected to said crystal to generate an analog voltage thereacross upon stressing of said crystal, an analog to digital converter connected to receive a voltage in accordance with the voltage on said output conductors to convert the analog signal of said crystal voltage output into a digital signal, and a digital readout gauge display connected to the output of said converter to display a digital value in accordance with the crystal voltage output.
1 An object o~ the invention is to provide a digital readout gauge which may be hand held and a portable self-contained unit.
Another object of the invention is to provide a digital readout tire pressure gauge.
Another object of the invention is to provide a digital readout force gauge utilizing a piezoelectric crystal~
Other objects and a ~uller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing.
':
Brief Description of the Drawing FIG. 1 is a longitudinal sectional view of the digital readout gauge embodying the invention;
FIG. 2 is a partial top view partly in sectio~ of the gauge of FIG. l;
FIG. 3 is a schematic diagram of the electrical circuit used in the digital gauge; and FIG. 4 is a longitudinal sectional partial view of 20 a modification. - ;
: .
Description of the Pre~erred Embodiments FIGS~ 1 and 2 show the mechanical construction o~ a digital readout gauge 11, which, in this embodiment is a portable self-contained unit. The gauge 11 includes a housing 12 and this housing includes a sleeve-like handle 14 telescoped over part o~
the housing. The housing also includes a nosepiece 13 secured to the housing in any suitable manner such as the threads 15.
The nosepiece 13 has a valve mouth 16 leading to a pressure chamber 17. The valve mouth 16 is adapted to be slidably 1 applied to and over an ordinary tire valve 18 having the usual depressable valve core 21 to open the valve mechanism itself.
A valve deflator 24 has a central axial projection 25 to engage and depress the end of the valve core 21. The valve deflator 24 carries a seal washer 29 which slidably seals against the internal bore of the valve mouth 16 and also resiliently seals against the end of the tire valve 18 to seal the air pressure from the tire within the pressure chamber 17. This air under pressure is admitted to the chamber 17 through apertures 30 in the valve deflator 24 and through a filter 31.
A conduit 33 leads from the valve deflator 24 to the chamber 17.
A movable wall 35 is provided in the pressure chamber 17 and in this embodiment this movable wall is a metal diaphragm 36 clamped between an annular ring 37 on the nosepiece 13 and a shoulder 38 on the housing 12.
An electrical circuit 43 is provided within the housing 12 and this electrical circuit may include integrated circuits and other miniature components mounted on a printed circuit board 44 slidably received in slots in the housing 12. One or more batteries 45 may be provided within the housing 12 with access to the batteries through a removable plug 46 in the handle 14. The batteries provide the electrical power to operate the electrical circuit 44.
The housing 12 includes an inner sleeve 47 within the telescoping tubular handle 14. A flanged bushing 48 is p.rovided in the end of the inner sleeve 47, and a spring 49 ac~s between the bushing 48 and the pluy 46, urging the handle 14 to the rear.
This is resisted by an inwardly turned shoulder 50 on handle 14 enyageable with an abutment 51 on the housing 12. A switch extension 52 is provided on the plug 46 to engage the battery 50 upon the yauge being pressed against the valve 18.
~, 1 A piezoelectric crystal 53 is mounted to ~e stressed in accordance with movement of the movable wall or diaphragm 36.
In this embodiment the crystal 53 is mounted in a suitable manner to the diaphragm, as by soft solder. Conductors are mounted to receive voltage from the crystal and this may be one conductor 54 connected to one face and another conductor connected to the opposite face, which conveniently may be a connection to the metal diaphragm 36 through the metal housing 12. A digital readout display 55 is provided in the housing 12, as better shown in FIG. 2. A reset switch 56 is provided in the housing 12 to reset the digital display to zero with the switch button 57 accessible from the exterior o~ the housing 12.
The closing of the extension 52 onto the rear-most battery 45 is a power switch which enables the readout display 55. In the preferred embodiment, the closing o~ this switch 52 energizes the entire electrical circuit 43.
FIG. 3 illustrates a preferred embodiment of the electrical circuit 43. This electrical circuit includes generally ~ the crystal 53 supplying a peak detec~or 60 in turn supplying an output to an analog to digital converter 61 and this supplies a digital signal to a segment decoder 62 which supplies the segment driving signals to the digital~readout display 55.
; The battery 45 supplies electrical energy to power the ; electrical circuit 43 through the power switch 52 to a voltage terminal 63. This is a positive voltage terminal supplying the peak aetector 60, digital display 55 and segment decoder 62.
This positive voltage terminal 63 also supplies a DC to DC
converter 64 which has a negative output voltage terminal 65 supplying negative operating voltages to the peak detector 60 and primarily to the analog to digital converter 61.
3L~ 7 1 The peak detector 60 includes an operational amplifier 68 having positive and negative power supply terminals connected to the positive and negative voltage terminals 63 and 65, respectively. The non-inverting input terminal 69 is connected through a resistor 70 to the output o~ the crystal 53. The output terminal 71 o~the operational amplifier 68 is connected through a forward conducting diode 72 and resistor 73 to a capacitor 74 to ground. Due to the diode 72 only positive outputs are supplied to the capacitor 74 which charges to the peak value of theoutput of the crystal 53, as multiplied by the gain of the operational amplifier 68. The output after the diode 72 is returned as a feedback connection to the inverting terminal 75 to establish the action of the operational amplifier 68 as a detector. The reset switch 56 is connected across the capacitor 74 to discharge this capacitor and reset the digital display 55 to zero.
The DC to DC converter 64 is utilized to provide a negative operating voltage at the terminal 65 and thus avoid the requirement for an additional batter~ to supply a negative operating voltage to the analog to digital converter 61~ This DC
to DC converter 64 is supplied with positive operating voltage from the terminal 63 and includes a transistor 7~, a field effect transistor 80, Zener diode 81, transformer 82, capacitor 83 and diode 84. The circuit acts as a high efficiency blocking oscillator-type converter. The self-oscillation charges the capacitor 83 and when the voltage across this capacitor reaches a value equal to the sum of the Zener voltage plus the pinch-off voltage of the FET transis~or 80, then the oscillations cease.
The circuit resumes oscillation when the output voltage falls below this value and it will be noted that the voltage across the capacitor 83 is the voltage at the negative output terminal 65.
8~7 1 The positive voltage supply terminal 63 supplies operating voltage to a current regulator 88 with the output connected through a potentiometer 89 and a resistor 90 to ground. The tap 91 of the potentiometer 89 is connected to supply current regulated power to the analog to digital converter 61 at a terminal 92. Terminal 93 o~ this converter 61 is connected to the negative supply terminal 65 for operating voltages. This converter 61 has an input at terminal 94 from the peak detector 60. It has a digital output on the lines 95 to the segment decoder 62. The output on these lines 95 is a digital output in a binary code of first, second and third bits relative to a common logic zero conductor. This binary code digital information is supplied to the segment decoder 62 which supplies the necessary signals through seven coupling resistors 96 to the seven-segment display numerals 97-99 of the digital readout display 55. The segment decoder 62 is a binary to decimal decoder changing the binary digital information into decimal type information for easy reading on the digital display 55. This also provides a floating decimal point indication with a reading of 0.10 to 99.9.
The display numerals 97-99 are each mounted through a driver transistor 101-103, respectively, to ~round. The bases of these transistors 101-103 axe connec~ed to the A/D converter 61 to turn on these transis~ors at the appropriate time to drive these numerals 97-99.
In one practical circuit constructed in accordance with the teachings of the invention, the peak detector 60 utilized an RCA CA3130 model operational amplifier, the current regulator 88 was a Siliconix, Inc. C~033 regulator, and the A/D converter 61 was a Siliconix, Inc. LD130 and the segment decoder 62 was a Texas Instruments, Inc. 74C48.
~0~L8~7 1 Operation The digital readout gauge 11 is usable as an extremely portable self-contained force gauge. Force applied to the movable wall 35 results in stressing the piezoelectric crystal 53 to develop a voltage on the output conductors 54. In the embodiment shown the gauge 11 is a pressure gauge and utilizes the pressure chamber 17. This chamber normally has only atmospheric pressure therein which is taken as the zero condition.
When the gauge 11 is applied to a tire type valve 18, for example, then the air pressure within the structure, such as a tire, is applied to the pressure chamber 17. This occurs because the valve mouth 16 is slid over the valve 18, the deflator projection 25 engages and depresses the valve core 21.
At the same time the seal washer 29 engages the end of the valve stem to seal the combined valve and pressure chamber 17 against external leakage. The resilience of the seal washer 29 accepts -~
slight differences in geometry of various valves 18. The telescoping of the housing 12 inside the handle 14 ac~uates the power switch 52. The closing of this switch permits illumination of the display 55, and in the preferred embodiment energizes the electrical circuit 43 contained with in the handle 14 and shown schematically in FIG. 3.
Let is be assumed thatthe pressure within the vessel - to whi~h the valve 18 i5 connected is 28.2 psi. This fluid pressure is passed through the aperture 30 into the pressure chamber 17 to move the diaphragm 36. This stresses the piezoelectric crystal 53 and develops an analog vol~age thereon - proportional to this pressure. The closing of the power switch 52 by application of the gauge to the valve has energized the electrical circuit 43 shown in FI~. 3. Accordingly, the analog 1 voltage developed by the crystal 53 will be passed to and amplified by the operational amplifier 68 connected as a peak detector 60. In one circuit constructed with the invention, the output of the crystal 53 was one millivolt per pound per square inch and accordingly, in the example above, the output of the crystal would be 28.2 millivolts. This voltage is amplified by the amplifier 6~ and passed to charge the capacitor 74. Even if the peak value of the pressure within the pressure chamber 17 decreases, the peak reading remains for a long period of time. This might be as much as ten minuies if desired. The reading may be sto,red as a charge on the capacitor 7~ and the impedance value of this capacitor is decreased to shorten the time of holding this peak value. If another force or pressure is to be measured shortly after the first such measurement, then the reset switch 56 should be closed momentarily to discharge the capacitor 74. Otherwise, the charge on this capacitor would only slowly decay and a false reading could be given if the second force or pressure is less than the first. This is true even though the power switch 52 is deactivated and again reacti-vated for the second measurement. This deactivation of the power switch 52 will deenergize the entire circuit 43 but does not discharge the capacitor 74.
The peak reading, iIl the above example 28.2 psi, is passed to the A/D converter 61. This is an analog voltage which is converted into a digital voltage in the form of binary bits on the conductors or lines 95. The segment decoder 62 is a binary to decimal converter which converts this binary coded information into a decimal information to drive the display numerals 97-99 of the digital readout display 55. In the ahove i8~7 1 example the numerals 28.2 will be displayed on the readout display 55 during energization of this circuit 43. If the gauge 11 is continuously applied to valve 18 and the reset switch 56 closed, then this will short and discharge the capacitor 74 so that the display 55 reads 00Ø
FIG. 4 illustrates a modified form of digital readout gauge 111 contained in the portable housing 112 having a nose piece 113. Many parts may be the same as in the embodiment of FIGS. 1 and 2 such as the valve mouth 16, the valve deflator 24, seal washer 29 and filter 31. The conduit 33 leads to a pressure chamber 117 which has a movable wall 135 and in this particular embodiment the movable wall 135 is the piezoelectric crystal 53 itself. This crystal is secured between a shoulder 137 on the nosepiece 113 and a resilient washer 138 in the housing 12. The orce within this pressure chamber 117 acts directly on the crystal 53 to move and stress this crystal so as to develop an output voltage on the output conductors 54 thereof. The remainder of the components may be the same as in the gauge 11 of F~GS. 1 and 2.
The gauges 11 and 111 illustrate a digital readout forc~ gauge which displays a d1gital signal on the display 55 which is proportional to an applied force, with the force being applied to stress the piezoelectric crystal 53. In each of these gauges the crystal is mounted to be stressed in accordance with the movement of a movable wall and this wall is in a pressure chamber which can at least momentarily contain the fluid pressure.
This contained fluid pressure stresses the movable wall and stresses the crystal. The entire gauge may be mounted in a very small and extremely portable housing 12 or 112 to easily be applied to a tire valve 18 for example, to determine the amount L8~7 1 of fluid pressure within this container to which th~ valve is at~ached. The sleeve 47 telescopes inside the tubular handle 14, as resisted by the spring 49. The power switch 52 is actuated by a change from the first position to a second pOSitiOIl of these two sleeves to energize the entire electrical circuit 43. This enables the digital readout display 55. The peak detector 60 maintains the peak reading observed within the pressure chamber 17, regardless of whether this pressure might decrease after its initial maximum value. The reset switch 56 is connected to discharge th~ capacitor 7~ so that the gauge - 11 or 111 is xeady for measurement of another and smaller value of force.
While we have illustra~ed and described a preferred embodiment of our invention, it will be understood that this is by way of example only and not to be construed as limiting.
6~15 ~ 8~ /77 N~MBER S~EET
11 digital readout gauge 68 op. amp.
12 housing 69 non-inverting input 13 nosepiece 70 resistor 14 handle portion 71 output of 68 15 threads . 72 diode 16 valve mouth 73 resistor 17 pressure chamber 74 capacitor 18 tire valve 75 inverting terminal 21 valve core 79 transistor 24 valve deflator 80 FET transis-tor 25 central projection ~1 Zener diode 26 82 transformer 27 ~3 capacitor 28 84 diode 29 seal washer 30 apertures 31 filter 88 current regulator 33 conduit 89 Pot 34 90 resistor 35 movable wall 91 blade of 89 36 diaphragm 92 terminal 37 annular ring 93 terminal 38 shoulder 94 terminal 95 lines 96 coupling resistors 97-99 numerals 101-103 driver transistor 43 electrical circuit 44 printed circuit board 45 batteries 46 removable plug 47 inner sleeve 48 ~langed b~ushing 49 spring 50 shoulder in 14 111 digital readout gauge 51 abutment in 12 112 housing 52 switch extension 113 nosepiece 53 piezoelectric crystal 54 conductors to 53 digital readout display 56 reset switch 117 pressure chamber 57 switch button 135 movable wall 137 shoulder .138 resilient washer 60 peak detector 61 A/D converter 62 segment decoder 63 ~voltage terminal 64 DC to DC converter 65 -voltage terminal
Accordingly the problem to be solved is how to achieve a small compact portable digital readout force gauge which is accurate and yet requires a minimum of electrical energy lnput.
, . .
Summary of the Invention This problem may be solved by a digital readout gauge, comprising, in combination, a housing, a chamber in said housing, wall means in said chamber movable with changes of force on said wall means, means to apply a changeable force on said wall means, an electrical circuit in said housing, a battery in said housing and connected to supply power to said electrical circuit, said electrical circuit including a piezoelectric crystal mounted to be stressed in accordance with movement of said movable wall means, output conductors connected to said crystal to generate an analog voltage thereacross upon stressing of said crystal, an analog to digital converter connected to receive a voltage in accordance with the voltage on said output conductors to convert the analog signal of said crystal voltage output into a digital signal, and a digital readout gauge display connected to the output of said converter to display a digital value in accordance with the crystal voltage output.
1 An object o~ the invention is to provide a digital readout gauge which may be hand held and a portable self-contained unit.
Another object of the invention is to provide a digital readout tire pressure gauge.
Another object of the invention is to provide a digital readout force gauge utilizing a piezoelectric crystal~
Other objects and a ~uller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing.
':
Brief Description of the Drawing FIG. 1 is a longitudinal sectional view of the digital readout gauge embodying the invention;
FIG. 2 is a partial top view partly in sectio~ of the gauge of FIG. l;
FIG. 3 is a schematic diagram of the electrical circuit used in the digital gauge; and FIG. 4 is a longitudinal sectional partial view of 20 a modification. - ;
: .
Description of the Pre~erred Embodiments FIGS~ 1 and 2 show the mechanical construction o~ a digital readout gauge 11, which, in this embodiment is a portable self-contained unit. The gauge 11 includes a housing 12 and this housing includes a sleeve-like handle 14 telescoped over part o~
the housing. The housing also includes a nosepiece 13 secured to the housing in any suitable manner such as the threads 15.
The nosepiece 13 has a valve mouth 16 leading to a pressure chamber 17. The valve mouth 16 is adapted to be slidably 1 applied to and over an ordinary tire valve 18 having the usual depressable valve core 21 to open the valve mechanism itself.
A valve deflator 24 has a central axial projection 25 to engage and depress the end of the valve core 21. The valve deflator 24 carries a seal washer 29 which slidably seals against the internal bore of the valve mouth 16 and also resiliently seals against the end of the tire valve 18 to seal the air pressure from the tire within the pressure chamber 17. This air under pressure is admitted to the chamber 17 through apertures 30 in the valve deflator 24 and through a filter 31.
A conduit 33 leads from the valve deflator 24 to the chamber 17.
A movable wall 35 is provided in the pressure chamber 17 and in this embodiment this movable wall is a metal diaphragm 36 clamped between an annular ring 37 on the nosepiece 13 and a shoulder 38 on the housing 12.
An electrical circuit 43 is provided within the housing 12 and this electrical circuit may include integrated circuits and other miniature components mounted on a printed circuit board 44 slidably received in slots in the housing 12. One or more batteries 45 may be provided within the housing 12 with access to the batteries through a removable plug 46 in the handle 14. The batteries provide the electrical power to operate the electrical circuit 44.
The housing 12 includes an inner sleeve 47 within the telescoping tubular handle 14. A flanged bushing 48 is p.rovided in the end of the inner sleeve 47, and a spring 49 ac~s between the bushing 48 and the pluy 46, urging the handle 14 to the rear.
This is resisted by an inwardly turned shoulder 50 on handle 14 enyageable with an abutment 51 on the housing 12. A switch extension 52 is provided on the plug 46 to engage the battery 50 upon the yauge being pressed against the valve 18.
~, 1 A piezoelectric crystal 53 is mounted to ~e stressed in accordance with movement of the movable wall or diaphragm 36.
In this embodiment the crystal 53 is mounted in a suitable manner to the diaphragm, as by soft solder. Conductors are mounted to receive voltage from the crystal and this may be one conductor 54 connected to one face and another conductor connected to the opposite face, which conveniently may be a connection to the metal diaphragm 36 through the metal housing 12. A digital readout display 55 is provided in the housing 12, as better shown in FIG. 2. A reset switch 56 is provided in the housing 12 to reset the digital display to zero with the switch button 57 accessible from the exterior o~ the housing 12.
The closing of the extension 52 onto the rear-most battery 45 is a power switch which enables the readout display 55. In the preferred embodiment, the closing o~ this switch 52 energizes the entire electrical circuit 43.
FIG. 3 illustrates a preferred embodiment of the electrical circuit 43. This electrical circuit includes generally ~ the crystal 53 supplying a peak detec~or 60 in turn supplying an output to an analog to digital converter 61 and this supplies a digital signal to a segment decoder 62 which supplies the segment driving signals to the digital~readout display 55.
; The battery 45 supplies electrical energy to power the ; electrical circuit 43 through the power switch 52 to a voltage terminal 63. This is a positive voltage terminal supplying the peak aetector 60, digital display 55 and segment decoder 62.
This positive voltage terminal 63 also supplies a DC to DC
converter 64 which has a negative output voltage terminal 65 supplying negative operating voltages to the peak detector 60 and primarily to the analog to digital converter 61.
3L~ 7 1 The peak detector 60 includes an operational amplifier 68 having positive and negative power supply terminals connected to the positive and negative voltage terminals 63 and 65, respectively. The non-inverting input terminal 69 is connected through a resistor 70 to the output o~ the crystal 53. The output terminal 71 o~the operational amplifier 68 is connected through a forward conducting diode 72 and resistor 73 to a capacitor 74 to ground. Due to the diode 72 only positive outputs are supplied to the capacitor 74 which charges to the peak value of theoutput of the crystal 53, as multiplied by the gain of the operational amplifier 68. The output after the diode 72 is returned as a feedback connection to the inverting terminal 75 to establish the action of the operational amplifier 68 as a detector. The reset switch 56 is connected across the capacitor 74 to discharge this capacitor and reset the digital display 55 to zero.
The DC to DC converter 64 is utilized to provide a negative operating voltage at the terminal 65 and thus avoid the requirement for an additional batter~ to supply a negative operating voltage to the analog to digital converter 61~ This DC
to DC converter 64 is supplied with positive operating voltage from the terminal 63 and includes a transistor 7~, a field effect transistor 80, Zener diode 81, transformer 82, capacitor 83 and diode 84. The circuit acts as a high efficiency blocking oscillator-type converter. The self-oscillation charges the capacitor 83 and when the voltage across this capacitor reaches a value equal to the sum of the Zener voltage plus the pinch-off voltage of the FET transis~or 80, then the oscillations cease.
The circuit resumes oscillation when the output voltage falls below this value and it will be noted that the voltage across the capacitor 83 is the voltage at the negative output terminal 65.
8~7 1 The positive voltage supply terminal 63 supplies operating voltage to a current regulator 88 with the output connected through a potentiometer 89 and a resistor 90 to ground. The tap 91 of the potentiometer 89 is connected to supply current regulated power to the analog to digital converter 61 at a terminal 92. Terminal 93 o~ this converter 61 is connected to the negative supply terminal 65 for operating voltages. This converter 61 has an input at terminal 94 from the peak detector 60. It has a digital output on the lines 95 to the segment decoder 62. The output on these lines 95 is a digital output in a binary code of first, second and third bits relative to a common logic zero conductor. This binary code digital information is supplied to the segment decoder 62 which supplies the necessary signals through seven coupling resistors 96 to the seven-segment display numerals 97-99 of the digital readout display 55. The segment decoder 62 is a binary to decimal decoder changing the binary digital information into decimal type information for easy reading on the digital display 55. This also provides a floating decimal point indication with a reading of 0.10 to 99.9.
The display numerals 97-99 are each mounted through a driver transistor 101-103, respectively, to ~round. The bases of these transistors 101-103 axe connec~ed to the A/D converter 61 to turn on these transis~ors at the appropriate time to drive these numerals 97-99.
In one practical circuit constructed in accordance with the teachings of the invention, the peak detector 60 utilized an RCA CA3130 model operational amplifier, the current regulator 88 was a Siliconix, Inc. C~033 regulator, and the A/D converter 61 was a Siliconix, Inc. LD130 and the segment decoder 62 was a Texas Instruments, Inc. 74C48.
~0~L8~7 1 Operation The digital readout gauge 11 is usable as an extremely portable self-contained force gauge. Force applied to the movable wall 35 results in stressing the piezoelectric crystal 53 to develop a voltage on the output conductors 54. In the embodiment shown the gauge 11 is a pressure gauge and utilizes the pressure chamber 17. This chamber normally has only atmospheric pressure therein which is taken as the zero condition.
When the gauge 11 is applied to a tire type valve 18, for example, then the air pressure within the structure, such as a tire, is applied to the pressure chamber 17. This occurs because the valve mouth 16 is slid over the valve 18, the deflator projection 25 engages and depresses the valve core 21.
At the same time the seal washer 29 engages the end of the valve stem to seal the combined valve and pressure chamber 17 against external leakage. The resilience of the seal washer 29 accepts -~
slight differences in geometry of various valves 18. The telescoping of the housing 12 inside the handle 14 ac~uates the power switch 52. The closing of this switch permits illumination of the display 55, and in the preferred embodiment energizes the electrical circuit 43 contained with in the handle 14 and shown schematically in FIG. 3.
Let is be assumed thatthe pressure within the vessel - to whi~h the valve 18 i5 connected is 28.2 psi. This fluid pressure is passed through the aperture 30 into the pressure chamber 17 to move the diaphragm 36. This stresses the piezoelectric crystal 53 and develops an analog vol~age thereon - proportional to this pressure. The closing of the power switch 52 by application of the gauge to the valve has energized the electrical circuit 43 shown in FI~. 3. Accordingly, the analog 1 voltage developed by the crystal 53 will be passed to and amplified by the operational amplifier 68 connected as a peak detector 60. In one circuit constructed with the invention, the output of the crystal 53 was one millivolt per pound per square inch and accordingly, in the example above, the output of the crystal would be 28.2 millivolts. This voltage is amplified by the amplifier 6~ and passed to charge the capacitor 74. Even if the peak value of the pressure within the pressure chamber 17 decreases, the peak reading remains for a long period of time. This might be as much as ten minuies if desired. The reading may be sto,red as a charge on the capacitor 7~ and the impedance value of this capacitor is decreased to shorten the time of holding this peak value. If another force or pressure is to be measured shortly after the first such measurement, then the reset switch 56 should be closed momentarily to discharge the capacitor 74. Otherwise, the charge on this capacitor would only slowly decay and a false reading could be given if the second force or pressure is less than the first. This is true even though the power switch 52 is deactivated and again reacti-vated for the second measurement. This deactivation of the power switch 52 will deenergize the entire circuit 43 but does not discharge the capacitor 74.
The peak reading, iIl the above example 28.2 psi, is passed to the A/D converter 61. This is an analog voltage which is converted into a digital voltage in the form of binary bits on the conductors or lines 95. The segment decoder 62 is a binary to decimal converter which converts this binary coded information into a decimal information to drive the display numerals 97-99 of the digital readout display 55. In the ahove i8~7 1 example the numerals 28.2 will be displayed on the readout display 55 during energization of this circuit 43. If the gauge 11 is continuously applied to valve 18 and the reset switch 56 closed, then this will short and discharge the capacitor 74 so that the display 55 reads 00Ø
FIG. 4 illustrates a modified form of digital readout gauge 111 contained in the portable housing 112 having a nose piece 113. Many parts may be the same as in the embodiment of FIGS. 1 and 2 such as the valve mouth 16, the valve deflator 24, seal washer 29 and filter 31. The conduit 33 leads to a pressure chamber 117 which has a movable wall 135 and in this particular embodiment the movable wall 135 is the piezoelectric crystal 53 itself. This crystal is secured between a shoulder 137 on the nosepiece 113 and a resilient washer 138 in the housing 12. The orce within this pressure chamber 117 acts directly on the crystal 53 to move and stress this crystal so as to develop an output voltage on the output conductors 54 thereof. The remainder of the components may be the same as in the gauge 11 of F~GS. 1 and 2.
The gauges 11 and 111 illustrate a digital readout forc~ gauge which displays a d1gital signal on the display 55 which is proportional to an applied force, with the force being applied to stress the piezoelectric crystal 53. In each of these gauges the crystal is mounted to be stressed in accordance with the movement of a movable wall and this wall is in a pressure chamber which can at least momentarily contain the fluid pressure.
This contained fluid pressure stresses the movable wall and stresses the crystal. The entire gauge may be mounted in a very small and extremely portable housing 12 or 112 to easily be applied to a tire valve 18 for example, to determine the amount L8~7 1 of fluid pressure within this container to which th~ valve is at~ached. The sleeve 47 telescopes inside the tubular handle 14, as resisted by the spring 49. The power switch 52 is actuated by a change from the first position to a second pOSitiOIl of these two sleeves to energize the entire electrical circuit 43. This enables the digital readout display 55. The peak detector 60 maintains the peak reading observed within the pressure chamber 17, regardless of whether this pressure might decrease after its initial maximum value. The reset switch 56 is connected to discharge th~ capacitor 7~ so that the gauge - 11 or 111 is xeady for measurement of another and smaller value of force.
While we have illustra~ed and described a preferred embodiment of our invention, it will be understood that this is by way of example only and not to be construed as limiting.
6~15 ~ 8~ /77 N~MBER S~EET
11 digital readout gauge 68 op. amp.
12 housing 69 non-inverting input 13 nosepiece 70 resistor 14 handle portion 71 output of 68 15 threads . 72 diode 16 valve mouth 73 resistor 17 pressure chamber 74 capacitor 18 tire valve 75 inverting terminal 21 valve core 79 transistor 24 valve deflator 80 FET transis-tor 25 central projection ~1 Zener diode 26 82 transformer 27 ~3 capacitor 28 84 diode 29 seal washer 30 apertures 31 filter 88 current regulator 33 conduit 89 Pot 34 90 resistor 35 movable wall 91 blade of 89 36 diaphragm 92 terminal 37 annular ring 93 terminal 38 shoulder 94 terminal 95 lines 96 coupling resistors 97-99 numerals 101-103 driver transistor 43 electrical circuit 44 printed circuit board 45 batteries 46 removable plug 47 inner sleeve 48 ~langed b~ushing 49 spring 50 shoulder in 14 111 digital readout gauge 51 abutment in 12 112 housing 52 switch extension 113 nosepiece 53 piezoelectric crystal 54 conductors to 53 digital readout display 56 reset switch 117 pressure chamber 57 switch button 135 movable wall 137 shoulder .138 resilient washer 60 peak detector 61 A/D converter 62 segment decoder 63 ~voltage terminal 64 DC to DC converter 65 -voltage terminal
Claims (21)
1. A digital readout gauge, comprising, in combination, a housing, a chamber in said housing, wall means in said chamber movable with changes of force on said wall means, means to apply a changeable force on said wall means, an electrical circuit in said housing, a battery in said housing and connected to supply power to said electrical circuit, said electrical circuit including a transducer mounted to be stressed in accordance with movement of said movable wall means, output conductors connected to said transducer to generate an analog voltage thereacross upon stressing of said transducer, an analog to digital converter connected to receive a voltage in accordance with the voltage on said output conductors to convert the analog signal of said transducer voltage output into a digital signal, and a digital readout display connected to the output of said to display a digital value in accordance with the transducer voltage output.
2. A digital readout gauge as set forth in Claim 1 wherein said wall means in said chamber seals said chamber.
3. A digital readout gauge as set forth in Claim 1, including means responsive to the application of force to one of said housing and chamber to enable said digital readout display.
4. A digital readout gauge as set forth in Claim 1, including switch means actuated in accordance with said means to apply a changeable force on said wall means, and means connecting said switch means in said electrical circuit to enable said digital readout display.
5. A digital readout gauge as set forth in Claim 1, wherein said electrical circuit includes a segment decoder connected to the output of said converter and supplying an output to said digital readout display.
6. A digital readout gauge as set forth in Claim 1, wherein said electrical circuit includes a DC to DC converter connected to said battery to establish a negative as well as a positive voltage relative to ground, and means connecting said negative voltage output of said DC to DC converter to said analog to digital converter.
7. A digital readout gauge as set forth in Claim 1, wherein said gauge is a pressure gauge, and said means to apply a force on said wall means includes means to apply a fluid pressure to said chamber.
8. A digital readout gauge as set forth in Claim 7, wherein said pressure gauge includes a standard adaptor in one end of said chamber and having a central deflator projection positioned to depress and open a valve core of a tire valve upon application of the adaptor to the tire valve.
9. A digital readout gauge as set forth in Claim 8, wherein said chamber is a pressure chamber, and including an annular seal washer surrounding said deflator projection to be engaged by any said tire valve to seal said pressure chamber to the tire valve.
10. A digital readout gauge as set forth in Claim g, including first and second telescoping sleeves in said housing, spring means urging said sleeves from a first toward a second position, switch means connected to be actuated upon relative movement of the sleeves to said first position, said electrical circuit including means to connect said switch means to enable energization of said electrical circuit from said battery, whereby said switch means turns on said electrical circuit upon application of said adaptor to a tire valve.
11. A digital readout gauge as set forth in Claim 1, wherein said electrical circuit includes a peak detector connected to detect the peak value of the analog signal from said transducer.
12. A digital readout gauge as set forth in Claim 11, wherein said peak detector includes an operational amplifier connected to amplify the signal from said transducer, and a diode connected to the output of said operational amplifier.
13. A digital readout gauge as set forth in Claim 11, wherein said electrical circuit includes a capacitor connected to be charged by said peak detector.
14. A digital readout gauge as set forth in Claim 13, wherein said capacitor provides an automatic turn off feature to extinguish the digital display upon discharge of the capacitor to a given value.
15. A digital readout gauge as set forth in Claim 14, wherein said electrical circuit includes a reset switch connected to discharge said capacitor to terminate said digital display.
16. A digital readout gauge as set forth in Claim 1, wherein said wall means includes a flexible metal diaphragm sealed in said chamber, and said transducer is mounted on the side of said diaphragm remote from said chamber to be stressed upon movement of said wall means.
17. A digital readout gauge as set forth in Claim 1, wherein said wall means is unitary with said transducer.
18. A digital readout force gauge, comprising in combination, a housing, a digital readout display mounted in said housing, an electrical circuit, electrical terminal means energizable to supply power to said electrical circuit, said electrical circuit including a transducer mounted to be stressed in accordance with an applied force, output conductors connected to said transducer to generate an analog voltage thereacross upon stressing of said transducer, an analog to digital converter connected to receive a voltage in accordance with the voltage on said output conductors to convert the analog signal of said transducer voltage output into a digital signal, and means connecting the output of said converter to said digital readout display to display a digital value in accordance with the transducer output.
19. A digital readout force gauge as set forth in Claim 18, wherein said electrical terminal means is a single polarity relative to ground, and including a DC to DC converter to establish an operating voltage of the opposite polarity and connected to operate said circuit.
20. A digital readout force gauge as set forth in Claim 18, including a peak detector connected to receive the output of said transducer and having an output to said converter.
21. A digital readout force gauge as set forth in Claim 20, wherein said peak detector includes an operational amplifier connected to amplify the signal from said transducer, and a diode connected to the output of said operational amplifier.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US85003677A | 1977-11-09 | 1977-11-09 | |
| US850,036 | 1977-11-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094847A true CA1094847A (en) | 1981-02-03 |
Family
ID=25307105
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA311,464A Expired CA1094847A (en) | 1977-11-09 | 1978-09-18 | Digital readout gauge |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5491258A (en) |
| CA (1) | CA1094847A (en) |
| DE (1) | DE2847330A1 (en) |
| FR (1) | FR2408825A1 (en) |
| GB (1) | GB2008255B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5301553A (en) * | 1989-12-20 | 1994-04-12 | Tjs Development Corporation | Apparatus for remote sensing and receiving |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0019463B1 (en) * | 1979-05-18 | 1986-02-12 | John Sansbury Knubley | Air dispensing apparatus |
| FR2529671A1 (en) * | 1982-07-05 | 1984-01-06 | Schrader Sa | DEVICE FOR MEASURING THE PRESSURE OF A FLUID AND AN INFLATOR-FREEZER ASSEMBLY USING THE DEVICE |
| US4642783A (en) * | 1984-06-11 | 1987-02-10 | Safe-Test, Inc. | Life raft testing device |
| GB2169411A (en) * | 1984-12-04 | 1986-07-09 | Albert Raymond Jordan | Programmable digital display tyre pressure gauge |
| US4704901A (en) * | 1986-05-19 | 1987-11-10 | Neotech Industries, Inc. | Tire pressure gauge |
| JPH02128549U (en) * | 1990-04-06 | 1990-10-23 | ||
| DE4133999C2 (en) * | 1991-10-14 | 1994-06-09 | Rainer Achterholt | Tire valve generating a pressure signal |
| GB2267347A (en) * | 1992-05-19 | 1993-12-01 | Huang Tien Tsai | Digital pressure gauge |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1286540A (en) * | 1968-12-13 | 1972-08-23 | Jisaku Murano | Device for detecting air amount in tyres of travelling vehicles or the like |
| US3831687A (en) * | 1970-07-13 | 1974-08-27 | Nat Controls | Flexure base scale |
| BE789172A (en) * | 1971-09-30 | 1973-01-15 | Reliance Electric Co | ELEKTRONISCH WEEGSTELSEL MET NUMERIEKE AFLEZING |
-
1978
- 1978-09-18 CA CA311,464A patent/CA1094847A/en not_active Expired
- 1978-10-16 GB GB7840644A patent/GB2008255B/en not_active Expired
- 1978-10-31 DE DE19782847330 patent/DE2847330A1/en not_active Withdrawn
- 1978-11-07 JP JP13635778A patent/JPS5491258A/en active Pending
- 1978-11-09 FR FR7831738A patent/FR2408825A1/en active Granted
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5301553A (en) * | 1989-12-20 | 1994-04-12 | Tjs Development Corporation | Apparatus for remote sensing and receiving |
| US5483826A (en) * | 1989-12-20 | 1996-01-16 | Tjs Development Corporation, Inc. | Remotely actuated pressure sensor responsive to an actuating signal |
| US5728933A (en) * | 1989-12-20 | 1998-03-17 | Sentech Corporation | System and method for remote sensing and receiving |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2008255A (en) | 1979-05-31 |
| FR2408825B1 (en) | 1983-07-01 |
| GB2008255B (en) | 1982-05-19 |
| DE2847330A1 (en) | 1979-05-17 |
| JPS5491258A (en) | 1979-07-19 |
| FR2408825A1 (en) | 1979-06-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |