JPH0215116B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a battery built-in type device that uses a digital displacement measuring device driven by a battery to transmit information by light to a processing device in a central control room. This invention relates to a digital displacement measuring device.

Conventionally, such mechanical displacement was detected by converting it into impedance such as capacitance or resistance, and the displacement was measured by amplifying and calculating the detection result using a differential amplifier or the like. Displacement measuring devices are well known. However, since such measuring devices generally use analog circuits, fluctuations due to natural disturbances such as noise and temperature are large, and therefore there is a certain limit to detection accuracy. In addition, when transmitting these measurement results to a remote central control room, for example, most of the methods to date use electrical signals.
It has the disadvantage that it is easily affected by noise, surge, etc., and therefore detection accuracy is reduced.

The present invention has been made in view of the above, and an object of the present invention is to provide a measuring device that is not significantly influenced by noise, temperature, surge, etc. as described above, and can improve measurement accuracy.

The features of this invention include a displacement measuring device that converts and measures mechanical displacement into physical quantities such as impedance, voltage, or frequency. By combining a digital arithmetic circuit section and a digital arithmetic circuit section, it is possible to use batteries, and by providing an optical-to-electrical or electrical-to-optical converter, it is possible to connect the upper processing device in the central control room. The point is that it made it possible to transmit information using light. Therefore, the synergistic effect of digitizing measurement equipment and avoiding noise and surges caused by optical transmission will further improve measurement accuracy.
This has the advantage that it can be used even in hazardous atmospheres such as explosives.

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 is a block diagram showing an overview of an embodiment of the present invention, Fig. 2 is a block diagram showing details of an embodiment of the invention, and Fig. 3 is a block diagram showing the details of an embodiment of the invention. A principle diagram to explain the principle of detection,
FIG. 4 is a time chart for explaining the operation according to the present invention, and FIG. 5 is a circuit diagram showing another embodiment of the capacitance detection section.

In FIG. 1, 1 is a detection section, and 2 is the detection section 1.
3 is a frequency conversion circuit, 4 is a counter, 5 is a timer, 6 is a reference clock generation circuit,
7 is a microprocessor (hereinafter also referred to as μ-COM arithmetic circuit), 8 is an optical transmission circuit, 9 is a power supply circuit using a battery, and 10 is a keyboard. The battery power supply circuit 9 supplies power to each required part within the measuring device, and is, for example, a self-charging type using a lithium battery, a solar battery and a NiCd (Nickel-Cadmium) battery, or a battery powered by optical power. It is possible to use a NiCd battery-powered device that operates. Each part of the measuring device according to the present invention configured in this manner further includes, as shown in FIG.
The detection section 1 here consists of two capacitors C ₁ and C ₂ , and the detection section selection circuit 2 consists of two capacitors C _{1 and} C 2 .
C ₂ and temperature measuring capacitor C _S , thermistor R _S
Consists of C-MOS type analog switch SW2 (SW21, SW22) that selects
The capacitance-frequency conversion circuit 3 is an analog switch that switches between charging and discharging the capacitors C ₁ and C ₂ and clears or resets the flip-flop Q1.
Set when SW1 (SW11, SW12) and the charging voltage of capacitor _C1 or _C2 exceed a predetermined voltage level (threshold level),
It consists of a flip-flop Q1 (D type) which is reset after a certain time determined by a predetermined time constant (resistance R _f and capacitor C _f ). In addition,
When using a conventional general D-type flip-flop, a circuit (for example, a Schmitt circuit) for determining the threshold level is installed in the preceding stage.
However, when a C-MOS type flip-flop is used, such a circuit is not required, and the switching voltage can be used as it is as the threshold voltage. Similarly, the timer 5 is composed of two-stage counters CT2 and CT3, and when the reset signal PO3 from the μ-COM arithmetic circuit 7 is released, the timer 5 starts counting the clock signal given from the reference clock generation circuit 6. (CT1) Counting is stopped by the count-up signal from 4. The μ-COM calculation circuit 7 is driven by a clock signal from the reference clock generation circuit 6 and performs various calculations and control operations. For example, send mode selection signals PO1 and PO2 to analog switch SW2 of detection section selection circuit 2 to select capacitor _C1 measurement mode, capacitor _C2 measurement mode, or temperature measurement mode (measurement using resistor R _S and capacitor C _S ). When not measuring, a reset signal PO3 is given to the counter 4 and timer 5 to reset them, and when measuring, the reset signal PO3 is released to perform counting operation, and the count up signal from the counter 4 is reset. is received as an interrupt signal IRQ, the count output from the timer 5 is read through terminals PI0 to PI15, and predetermined arithmetic processing is performed. μ−
The COM calculation circuit 7 includes a keyboard 10 for instructing operations to adjust the zero point or span to avoid measurement errors, and a reference clock generation circuit 6 or μ-COM calculation circuit 7 to save power. A standby mode circuit 12 for intermittent operation, an optical transmission circuit 8 for exchanging information by light with a host computer in a control room, and a light emitting diode in the circuit 8.
The LED abnormality detection circuit 11 and the like are connected.
The optical transmission circuit 8 mainly consists of a photodiode PD that receives optical signals from a host processing device or a computer, and a light emitting diode LED that transmits optical signals to the host processing device. This enables information transmission.

Here, the detection principle when converting the amount of mechanical displacement into capacitance and detecting it will be explained.

In FIG. 3A, a movable electrode EL _V is arranged between two fixed electrodes EL _F , and the movable electrode EL _V is moved to the left or right of the figure (see arrow R) according to the displacement of a physical quantity such as pressure or a mechanical quantity. ) direction. In this case, when one of the capacitances CA ₁ and CA ₂ between the electrodes increases, the other decreases, that is, they change differentially. Here, the area of each electrode is S, the dielectric constant between the electrodes is ε, and the movable electrode EL _V
For example, if the distance between the fixed electrode EL _F and the fixed electrode EL F is d,
The capacitances CA ₁ and CA ₂ when the movable electrode _ELV is displaced by Δd as shown by the dotted line are calculated as CA ₁ =εA/(d−Δd) CA ₂ =εA/(d+Δd). Now, considering the sum and difference of these capacitances, CA ₁ + CA ₂ = εA・2d/(d ² − (Δd) ² ) CA _{1 −} CA ₂ = εA・2Δd/(d ² − (Δd) ² ), and therefore, by taking the ratio, (CA ₁ − CA ₂ )/(CA ₁ + CA ₂ )=Δd/d is obtained, and the displacement Δd is expressed as the capacitance value (CA ₁ − CA ₂ )/
It can be obtained by (CA ₁ + CA ₂ ).

Similarly, in FIG. 3B, two fixed electrodes EL _F
In contrast, when the movable electrode _ELV is arranged as shown in the figure and is displaced by Δd to the dotted line position in the figure due to external displacement, the following will occur. In this case, the capacity CA ₁
is fixed and CA ₂ is variable, and its values can be expressed as CA ₁ =εA/d, CA ₂ =εA/(d+Δd) in the same way as above. Therefore, considering these differences, CA ₁ − CA ₂ = εA・Δd/d(d+Δd), and therefore, taking the ratio of CA ₁ − CA ₂ and CA ₂ , (CA ₁ − CA ₂ )/CA ₂ =Δd/d, and the displacement amount Δd can be detected as a change in capacitance value.

The operation of the measuring device according to the present invention, which measures the amount of mechanical displacement based on such a detection principle, will be explained below with reference to FIGS. 2 and 4.

In the initial state, the mode selection signals PO1 and PO2 are not given from the μ-COM arithmetic circuit 7,
Counter (CT1) 4 is reset by reset signal PO3.
and timer 5 are in a reset state. Here, the measurement mode signal of capacitor _C1 as shown in Figure 4A is given, and the reset signal as shown in Figure 4B is applied.
When PO3 is released, capacitor C ₁ and switch
Since a path consisting of SW21, SW11, resistor R, and power supply _VDD is formed, capacitor _C1 is charged as shown in FIG. 4C. When this charging voltage exceeds the threshold voltage _VTH of flip-flop Q1 after _one hour t, flip-flop Q1 is set and an output is obtained from its output terminal Q. This output is applied to resistor R _f and capacitor C _f as well as to analog switch SW1. As a result, switch SW12 is opened and a charging circuit is formed by resistor R _f and capacitor C _f . At this time, the switch SW11 is switched to the position indicated by the dotted line, and the capacitor _C1 is discharged. When the charging voltage of the capacitor C _f reaches a predetermined value after a predetermined time t _C as shown in FIG. An output pulse of t _C is obtained. Note that analog switch SW1 is also turned off by resetting flip-flop Q1, so switch SW12
returns to the state shown in FIG. 2, forming a discharge circuit for capacitor C _f . The above time t ₁ is the capacitor C ₁
Since it is proportional to the size of the resistor R, a pulse signal with a frequency proportional to the capacitance of the capacitor _C1 is obtained from the output of the flip-flop Q1. This pulse signal is counted by the counter 4, and when it reaches a predetermined number, it emits a pulse (count UP output) as shown in FIG.
The count is stopped as shown in Figure 4 (G). The timer 5 counts the clock pulses from the pulse generation circuit 6 when the reset signal PO3 is released, and the counting result is sent to the terminals PI0 to PI by the μ-COM arithmetic circuit 7 which receives the count up signal from the counter 4.
15.

Here, if the threshold voltage of the flip-flop Q1 is V _TH , it is expressed as V _TH = V _DD (1-e ^-t1/RC1 ), and therefore, the charging time _{t 1 (} the (see Figure 4 D) is expressed as t ₁ =-RC ₁ log _e (1-V _TH /V _DD ).

Further, the above-mentioned time t _C is similarly expressed as t _C =-R _f C _f log _e (1-V _TH /V _DD ). Note that since the values of R _f and C _f are known, the above-mentioned time t _C is selected to be constant.

Therefore, by counting the clock pulses from the reference clock generation circuit 6 until the charging and discharging operation of the capacitor _C1 is counted n times, that is, by the output from the timer 5, the capacitor _{C1 is}
The charging/discharging time T ₁ can be determined by As _{is clear} from _FIG .
-1) times, it can be obtained as T ₁ = nt ₁ + (n-1) t _C ... (). In addition, like this, n
The time measurement counter CT2 counts the times.
This is to improve the resolution of the CT 3, and the number n of the clocks is appropriately selected depending on the output frequency of the reference clock generating circuit 6, the resistance value of the resistor R, the capacitance value of the capacitor _C1 , etc.

After determining the charging/discharging time T of the capacitor _C1 in this way, the μ-COM calculation circuit 7 outputs the signal PO1.
Alternatively, switch SW21 using PO2 to set the detection mode for capacitor _C2 , and
Measure the charge/discharge time _T2 of _C2 . The operating mode in this case is exactly the same as above, and the time chart thereof is shown in the right half of FIG. Note that the charging/discharging time T ₂ is calculated as follows in the same manner as in equation (1): T ₂ =nt ₂ +(n-1)t _C . . . ().

In the μ-COM arithmetic circuit 7, the above (I), ()
The following calculation is performed from the formula.

T ₁ +T ₂ -2(n-1)t _C = -nR(C ₁ +C ₂ ) log _e (1-V _T
H /V _DD ) T ₁ −T ₂ = −nR (C ₁ − C ₂ ) log _e (1−V _TH /V _DD ) T ₁ −T ₂ /
T ₁ +T ₂ -2(n-1)t _C =C ₁ -C ₂ /C ₁ +C ₂ ... () As is clear from the explanation in the previous principle diagram, this formula is proportional to the amount of displacement, so μ -COM calculation circuit 7 can determine the amount of displacement by performing the calculations described above.

In addition, in the above example, the amount of mechanical displacement, for example, the differential pressure ΔP, was measured by differentially changing the capacitance of capacitors C ₁ and C ₂ , but as shown in FIG. It is clear from the explanation of the principle diagram above that the present invention can be similarly applied to a case where C ₂ is fixed on the one hand and C ₁ is variable on the other hand. However, in this case, the pressure P is determined instead of the above-mentioned differential pressure ΔP, and the calculation formula thereof is expressed as follows in the same manner as above.

_P =C ₁ −C ₂ /C ₂ =T ₁ −T ₂ /T ₂ −(n-1)t good.

That is, FIG. 6 is a circuit diagram showing another embodiment of the detection section, and is an example in which the resistance changes. The detection principle in this case is exactly the same as in the case of capacitance; in this case, the resistance value is detected by taking advantage of the fact that the charging and discharging time is proportional to the product of the resistor and the capacitor. It is. Therefore,
Capacitor C shown in figures a to c is a fixed capacitor whose capacitance value is known, and R _X , R ₁
and R ₂ are measurement resistances, and R _C is a resistance with known resistance. Further, SW11 and SW21 are switches similar to those shown in FIG. 2 above, and Q1 is a flip-flop. In other words, what is shown in _{FIG .}
In addition, when the switch SW21 is switched to the opposite side as shown in the figure, the charging and discharging time T ₂ due to the fixed resistor R _C is determined, and R _X /R _C =T ₁ -(n-1)t _C /T ₂ -(n- 1) The resistance value of R _X is determined by the calculation t _C. The case shown in Figure b is the case where the line resistance R _l varies, and the charge/discharge time by the resistors R _x +2 R _l and R _C is changed by sequentially switching the switch
T _{1 , T 2 and T 3 are} determined, _respectively , and _R Moreover, the one shown in FIG. 3C is exactly the same as the one in which the capacitor C in the embodiment of the present invention is replaced with a resistor R, and its calculation formula is also expressed as the following equation.

R ₁ −R ₂ /R ₁ +R ₂ =T ₁ −T ₂ /T ₁ +T ₂ −2(n-1) _tCFigure 7 is a circuit diagram showing yet another embodiment of the detection section, in which the frequency This is a case of change.

In this case, the frequency itself changes, so
There is no need for frequency conversion as in the embodiment of FIG. 2, and therefore the output of the detection section is directly introduced into the counter via the amplification section. In this case, the count value of the counter is N, and the output value of the timer is T
Then, the frequency F is expressed as N/T.

FIG. 8 is a circuit diagram showing another embodiment of the detection section,
This is the case when the voltage changes.

Capacitor C and switch SW1 in the same figure
1, SW21 and flip-flop Q1 are similar to those shown in the previous figures, and OP1, OP
2 is an operational amplifier. The measured voltage _E1 amplified by the operational amplifier OP1 is transferred to the operational amplifier OP2.
is compared with a quantity proportional to the integral value of a constant current by capacitor C, and the integral voltage becomes the measured voltage.
When _E1 is exceeded, flip-flop Q1 is set. In other words, since the threshold level explained in FIG. 2 changes according to the voltage to be measured, it is possible to obtain a time signal according to the input voltage, as in the case of measuring capacitance or resistance. Note that the arithmetic expression in this case is expressed as the following equation.

C _X E ₁ / I = T ₂ - T ₁ In the above equation, _{E 1} is _the voltage to be measured, C Measurement time when switch SW21 is switched to the opposite side from that shown, T ₂
is the measurement time in the illustrated state. Incidentally, no matter which detection method is used, according to the present invention, the problem can be easily handled by simply selecting an appropriate program.

The measurement results thus measured are transmitted to the host computer by the light emitting diode LED of the optical transmission circuit 8, if necessary. The optical transmission method in this case is the conventionally well-known PWM (pulse width modulation).
or PCM (Pulse Code Modulation) method, or simply transmitting an optical signal of a predetermined frequency or wavelength, and further multiplexing and transmitting when connecting multiple measuring devices. be able to.

As described above, according to the present invention, a measured quantity is converted into a digital quantity by a capacitor (resistor) and a capacitance (resistance)-frequency conversion part, and a digital calculation is performed by the first and second counting parts and the digital calculation circuit part. Since the amount of mechanical displacement is measured at the same time, the effects of noise and temperature can be avoided, making it possible to improve measurement accuracy and save power consumption. can. In addition, since it is possible to transmit information between the measuring device and the host computer using light, it is not affected by noise or surges, so it is possible to improve measurement accuracy from this point of view as well. It has the advantage that it can be used even in an atmosphere where there is a risk of.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an overview of an embodiment of this invention, Fig. 2 is a block diagram showing a detailed embodiment of this invention, and Fig. 3 is a diagram showing a structure in which mechanical displacement is converted into a capacitance value. A principle diagram for explaining the detection principle, FIG. 4 is a time chart for explaining the operation according to the present invention, FIG. 5 is a circuit diagram showing another embodiment of the capacitance detection section, and FIG. 6 is a resistance detection FIG. 7 is a circuit diagram showing an embodiment of the frequency detection section, and FIG. 8 is a circuit diagram showing an embodiment of the voltage detection section. Description of symbols 1...detection section, 2...detection section selection circuit,
3...Capacitance-frequency conversion circuit, 4...Counter, 5...
Timer, 6...Reference clock generation circuit, 7...μ-
COM operation circuit, 8... Optical transmission circuit, 9... Battery power supply circuit, 10... Keyboard, 11... LED abnormality detection circuit, 12... Standby mode circuit, C ₁ ,
C ₂ , C _S ... capacitor, Q1 ... flip-flop,
SW1, SW2...Analog switch, CT1~CT
3...Counter.

Claims (1)

[Claims] 1. Two capacitors whose capacitance values differentially change according to mechanical displacement, and a charging/discharging circuit that charges each of the capacitors in a time-sharing manner and discharges them over a fixed period of time. , a capacitance-frequency conversion unit that converts the time required for charging and discharging into a pulse signal with a frequency corresponding to the capacity, and counting the number of pulses from the conversion unit, and counting when the counted value reaches a predetermined value. a first counting section that outputs an output; and a second counting section that starts counting clock pulses from a clock signal source when each of the capacitors starts charging or discharging, and stops counting the clock pulses according to a counting output from the first counting section. 2 counting section; and a second counting section receiving the count output from the first counting section;
A digital calculation circuit unit that reads the counting results of the counting unit and calculates the amount of mechanical displacement by calculating the following equation (1) based on the results, an optical-electrical converter that converts the calculation results into an optical signal, and an external circuit. a transmission circuit section equipped with an electric-to-optical converter that converts an optical signal from the optical signal into an electrical signal, and a battery power supply that supplies power to each of the sections, and the transmission circuit section is provided with a transmission circuit section that is connected to a higher-level processing device via the transmission circuit section. 1. A digital displacement measuring device with a built-in battery capable of transmitting information by light, characterized in that by being connected to the processing device, information can be transmitted by light. (T ₁ - T ₂ )/(T ₁ + T _{2 -} K) ...(1) T ₁ ; Counting result when measuring one capacitor T ₂ ; Counting result when measuring the other capacitor K: Constant 2 It has two capacitors, one of which has a fixed capacitance value and the other whose capacitance value changes according to mechanical displacement, and a charging/discharging circuit that charges each of the capacitors in a time-sharing manner and discharges them over a fixed period of time. , a capacitance-frequency conversion unit that converts the time required for charging and discharging into a pulse signal with a frequency corresponding to the capacity, and counting the number of pulses from the conversion unit, and counting when the counted value reaches a predetermined value. a first counting section that outputs an output, and starts counting clock pulses from a clock signal source when each of the capacitors starts charging or discharging, and stops counting the clock pulses according to a count output from the first counting section; a second counting section; and a second counting section receiving the counting output from the first counting section;
A digital calculation circuit unit that reads the counting results of the counting unit and calculates the amount of mechanical displacement by calculating the following equation (1) based on the results, an optical-electrical converter that converts the calculation results into an optical signal, and an external circuit. a transmission circuit section equipped with an electric-to-optical converter that converts an optical signal from the optical signal into an electrical signal, and a battery power supply that supplies power to each of the sections, and the transmission circuit section is provided with a transmission circuit section that is connected to a higher-level processing device via the transmission circuit section. 1. A digital displacement measuring device with a built-in battery capable of transmitting information by light, characterized in that by being connected to the processing device, information can be transmitted by light. (T ₁ −T ₂ )/(T ₂ −K) …(1) T ₁ ; Counting result when measuring one capacitor T ₂ ; Counting result when measuring the other capacitor K; Constant 3 Machine It has two resistors whose resistance value differentially changes depending on the displacement of the capacitor, and a charging/discharging circuit that charges a predetermined capacitor in a time-sharing manner through each of the resistors and discharges it over a fixed period of time. , a resistance-frequency converter that converts the time required for charging and discharging into a pulse signal with a frequency corresponding to the resistance; and a resistance-frequency converter that counts the number of pulses from the converter and counts when the counted value reaches a predetermined value. a first counting section that outputs an output, and starts counting clock pulses from a clock signal source when each of the capacitors starts charging or discharging, and stops counting the clock pulses according to a count output from the first counting section; a second counting section; and a second counting section receiving the counting output from the first counting section;
A digital calculation circuit unit that reads the counting results of the counting unit and calculates the amount of mechanical displacement by calculating the following equation (1) based on the results, an optical-electrical converter that converts the calculation results into an optical signal, and an external circuit. a transmission circuit section equipped with an electric-to-optical converter that converts an optical signal from the optical signal into an electrical signal, and a battery power supply that supplies power to each of the sections, and the transmission circuit section is provided with a transmission circuit section that is connected to a higher-level processing device via the transmission circuit section. 1. A digital displacement measuring device with a built-in battery capable of transmitting information by light, characterized in that by being connected to the processing device, information can be transmitted by light. (T ₁ - T ₂ )/(T ₁ + T _{2 -} K) ...(1) T ₁ ; Counting result when measuring one resistor T ₂ ; Counting result when measuring the other resistor K ;Constant 4 Two resistors, one of which has a fixed resistance value and the other whose resistance value changes according to mechanical displacement, and a capacitor that is charged in a time-sharing manner through each of the resistors and charged for a certain period of time. a resistance-frequency conversion section that converts the time required for charging and discharging into a pulse signal with a frequency corresponding to the resistance; and a resistance-frequency conversion section that counts the number of pulses from the conversion section and calculates the counted value. a first counting section that outputs a counting output when a predetermined value is reached; and a first counting section that starts counting clock pulses from a clock signal source when each of the capacitors starts charging or discharging; a second counting section that stops counting the clock pulses when the clock pulses reach the second counting section;
A digital calculation means that reads the counting result of the counting section and calculates the amount of mechanical displacement by calculating the following equation (1) based on the result, an optical-electrical converter that converts the calculation result into an optical signal, and an external a transmission circuit section equipped with an electric-to-optical converter that converts an optical signal into an electric signal; and a battery power supply that supplies power to each of the sections, and is connected to a higher-level processing device via the transmission circuit section. 1. A digital displacement measuring device with a built-in battery capable of transmitting information by light, characterized in that information can be transmitted by light between the processing device and the processing device. (T ₁ −K)/(T ₂ −K) …(1) T ₁ ; Counting result when measuring one resistor T ₂ ; Counting result when measuring the other resistor K: Constant