JPS596438B2 - displacement transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a displacement converter that converts an amount of mechanical displacement into an electrical signal using changes in capacitance and inductance.

Conventionally, there is a device of this type in which an alternating current signal is applied to capacitance or inductance, and displacement is detected from a change in current or voltage based on a change in capacitance or inductance.

However, such conventional devices have the drawback that fluctuations in the amplitude and frequency of the applied alternating current signal, fluctuations in the power supply voltage, or the influence of the ambient temperature directly result in errors. The present invention aims to realize a displacement transducer of this type that does not have these drawbacks and can obtain an output signal as a pulse width signal or an analog signal.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, 0SC is an oscillator, which includes an amplifier A made up of transistors, reactances R1 and R2 representing capacitors or inductances, and reactances R1 and R2.
It consists of a resonant circuit F consisting of a first changeover switch S, which alternately switches the connection of
It is determined by the circuit constant of the resonant circuit F including reactance R1 or R2. Here, an object (not shown) to which mechanical displacement is applied is placed in the vicinity of the first reactance R1, and a fixed object (not shown) made of the same material as the displacement object is placed in the vicinity of the second reactance R2. (not shown) are arranged, and these constitute a displacement detection section. Figures 2 to 6
The figure is a configuration diagram showing an example of this displacement detection section.

FIG. 2 shows electrodes 23 and 2 adjacent to fixed electrodes 21 and 22.
4, one electrode 23 serves as a displacement object, and is adapted to be displaced in the direction of arrow a in response to mechanical displacement.

The spaces between each electrode 21 and 23 and between 22 and 24 constitute reactance (capacitance) Rl and R2, respectively, and when the electrode 23 is displaced in the direction a, the space between the electrodes 21 and 23
The distance changes, and the first reactance R1 changes.
In FIG. 3, the displacement direction of the electrode 23 is set in the direction of the arrow a in the one shown in FIG.
1 and 23 change, and the first reactance R1
is subject to change.

FIG. 4 shows, for example, core rods 27, 2 inside the coils 25, 26.
8, one core rod 2r is mechanically displaced and displaced in the direction of arrow a, thereby changing the reactance (inductance) R1 of the coil 25. Figure 5 shows a core 27 configured in a U-shape,
The coils 25 and 26 are wound around the core 27.
, 28, the iron pieces 23 and 24 are arranged in close proximity to the magnetic pole pieces of , 28,
The reactance of the coil 25 is changed by mechanically displacing one iron piece 23 and displacing it in the direction of arrow a. Figure 6 shows the coil 25
, 26, and mechanically displaces one of the plates 23 in the direction of arrow a, thereby changing the reactance of the coil 25. It is.

Returning to FIG. 1, PLS is a pulsing circuit connected to the output terminal of the oscillator OSC (7), and UDC is an up-down counter.

S2 is a second changeover switch, which is provided between the pulsing circuit PLS and the up/down counter UDC. DL
C is a digital logic circuit which takes the output of the up-down counter UDC as an input signal, and here the upper limit setting value U is preset.
S and a lower limit set value DS are set, and the counter U
When the contents of DC reach US or DS, changeover switches Sl, S2 and changeover switch S3, which will be described later, are driven. E is a DC power supply, Rl and r2 are resistors connected to the DC power supply E, and S3 is a changeover switch driven by the output of the digital logic circuit DLC, and these constitute a pulse width signal generation circuit. The LPF is a reduced frequency filter that smoothes the pulse width signal obtained from the switch S3.
The operation of the apparatus configured in this way will be explained next. First, it is assumed that the changeover switches Sl, S2, and S3 are connected to the contact U side (this state is called phase 1).
In this phase 1, the oscillator 0SC has its feedback circuit F
includes a first reactance R1, and the oscillation frequency F changes in response to a change in the first reactance R1, that is, a mechanical displacement. The oscillation output of the oscillator 0SC is turned into a pulse signal by the pulse generator PLS, which is applied to the up terminal U of the up down counter UDC and counted (added). As a result, the up-down counter U
The contents of DC are oscillation frequency f1,
That is, it increases with a slope corresponding to the mechanical displacement position. Digital logic circuit DLC is up-down counter UDC
When this reaches the preset upper limit US, switches S, S2 and S3 are input.
is connected to the contact D side (this state is called phase 2). In this phase 2, the oscillator OSC has a configuration in which its feedback circuit F includes the second reactance R2, and its oscillation frequency becomes a constant value F2 independent of mechanical displacement. This oscillation frequency F2 is pulsed by the pulse generator PLS and then applied to the down terminal U of the up/down counter UDC via the second changeover switch S2 to count (
subtraction). As a result, the up-down counter UDC
As shown in Figure R, the content of the arrow now descends at a constant angle of inclination. Then, when the contents of the counter UDC reach the lower limit set value DS, the digital logic circuit DLC detects this and connects the changeover switches Sl, S2 and S3 to the terminal U side again to set the phase 1 state. From now on Phase 1
, Phase 2 are repeated, and Phase 1 is repeated from the output side of the logic circuit DLC and the changeover switch S3 as shown in FIG.
A pulse width signal having pulse widths Tl and t2 corresponding to phase 2 and phase 2 can be obtained. Here, the pulse width t
1 is the oscillation frequency F at phase 1 of the oscillator 0SC,
, that is, it corresponds to the mechanical displacement, and the pulse width T2 becomes the oscillation frequency F2 at the time of phase 2, that is, a constant value. Therefore, a pulse width signal whose duty ratio ("1") corresponds to the mechanical displacement can be obtained via the switch S3.

Further, by applying this pulse width signal to the low frequency filter LPF, a DC voltage corresponding to the mechanical displacement can be obtained from this output terminal 0UT. FIG. 9 is a block diagram showing another embodiment of the present invention.

In this embodiment, the first reactance R1 and the second reactance R2 are configured to differentially change with respect to mechanical displacement. FIGS. 10 to 14 are configuration diagrams showing examples of the displacement detection section in this case.

10 and 11 have fixed electrodes 23 and 24 arranged on both sides of a displacement object 20 to which mechanical displacement is applied, and both are fixed between the displacement object 20 and the fixed electrode 23 and between the displacement object 20 and the displacement object 20. Reactance (capacitance) R and R2 formed between the electrodes 24 change operationally in response to mechanical displacement. 12 to 14 show coils 25 and 26 arranged at both ends of a displacement object 20, and the reactance (inductance) thereof changes differentially in response to the displacement of the displacement object 20. FIG. In this way, the first
If the values of reactance R1 and second reactance R2 are configured to vary differentially with respect to mechanical displacement, the oscillator 0S in phase 1 and phase 2
The oscillation frequencies f1 and F2 obtained from C vary differentially in response to mechanical displacement.

Therefore, the pulse width Tl obtained from the logic circuit DLC
, t2 change differentially in response to mechanical displacement, making it possible to improve conversion sensitivity. Also, in this example,
Pulse width signal (drive signal) obtained from logic circuit DLC
and a standard frequency from a standard frequency generator CL, and a phase frequency detector PFD and a low-frequency edge wave circuit LPF2 are provided, which input the signal and the standard frequency from the standard frequency generator CL, and compare the phases of both signals. The reactance R3,R of
The constant of 4 or the power supply (not shown) of the oscillator 0SC is adjusted so that the period t1+T2 of the pulse width signal obtained from the logic circuit DLC is always maintained at a constant value that matches the period of the standard frequency signal. I have to. By maintaining the period t1+T2 at a constant value in this manner, the pulse width t1 and/or T2 accurately corresponds to the displacement. Note that in the circuits of Figure 1 and Figure 9, the oscillation operation of the oscillator may become unstable when switching between phase 1 and phase 2, so the oscillation output immediately after switching to each phase is measured using an up-down counter. It is also possible to add circuit means that does not apply any voltage to the voltage.

Figures 15 to 17 show an oscillator 0 that can be used in the device of the present invention.
It is a specific circuit diagram of SC.

In each figure, the oscillator 0S shown in Figure 1 or Figure 9
Elements corresponding to each element of C are given the same reference numerals. The one in Figure 15 is a Colpitts-type oscillation circuit, in which the inductive reactance R1 and/or R2 changes in response to displacement.The one in Figure 16 is a Hartle-type oscillation circuit, in which capacitive reactance R1 and/or R2 changes in response to displacement. . The circuit shown in FIG. 17 is a Clapp type oscillator circuit, and like the circuit shown in FIG. 15, the inductive reactance R1 and/or R2 changes in response to displacement.

These oscillation circuits are appropriately selected and used depending on the configuration of the displacement detection section and others.

As explained above, the device according to the present invention prepares two sets of reactances connected to the resonant circuit of the oscillator, changes the reactance in response to mechanical displacement, and alternately connects the reactances to the resonant circuit. When connected, two types of frequency signals obtained from an oscillator are converted into a pulse width signal corresponding to displacement using an up-down counter and a logic circuit, and has the following features.

(1) Effects such as changes in the ambient temperature of the oscillator, fluctuations in the oscillator's power supply voltage, or changes in the oscillator's components over time will cause errors at the same rate in Phase 1 and Phase 2, but they will cause errors in the up-down counter. Since these are canceled out by counting, they do not appear in the output signal.

Therefore, conversion errors due to ambient temperature, oscillator power supply voltage fluctuations, etc. can be removed. (;i) A signal corresponding to the displacement can be obtained as a pulse width signal.

Further, if necessary, it can be obtained as a DC signal via a low frequency wave circuit.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing one embodiment of the present invention, Figures 2-
FIG. 6 is a configuration diagram of the displacement detection section used in the device shown in FIG.
7 and 8 are waveform diagrams for explaining the operation of the device shown in FIG. 1, FIG. 9 is a block diagram showing another embodiment of the present invention, and FIGS. 10 to 14 are waveform diagrams for explaining the operation of the device shown in FIG. 9. 15 to 17 are specific circuit diagrams of an oscillator that can be used in the device of the present invention. 0SC...Oscillator, A...Amplifier, F
...Resonance circuit, R1...First reactance, R2...Second reactance, R3,
R4...Reactance, PLS...Pulse circuit, UDC...Up/down counter, DLC...Logic circuit, S1-S3...
・Selector switch, LPF, LPFl, LPF2...
...Low-frequency deep wave circuit, CL...Standard frequency generator, PFD...Phase frequency detector.

Claims (1)

[Claims] 1. A first reactance and a second reactance, which are arranged in the same environment and only one of which changes in response to mechanical displacement, or both of which change differentially; an oscillator in which one of the second reactances is alternately connected by a first changeover switch to constitute a resonant circuit; an up/down counter having an addition terminal and a subtraction terminal;
The first changeover switch is connected between the output terminal of the oscillator and the input terminal of the up/down counter, and when the first changeover switch connects the first reactance to the resonant circuit, the output terminal of the oscillator is connected to the addition terminal of the counter. Connect said second
a second changeover switch that operates in synchronization with the first changeover switch so as to connect the output terminal of the oscillator to the subtraction terminal of the counter when the reactance of the up-down counter is connected to the resonant circuit; When the counted value reaches a preset upper limit value, the second changeover switch switches to the subtraction terminal side of the up/down counter, and when the lower limit value reaches the lower limit value, the second changeover switch switches to the subtraction terminal side of the up/down counter. a logic circuit that controls the first and second changeover switches so that the switches are switched to the addition terminal side of the up/down counter; and a pulse width signal corresponding to the mechanical displacement is output from an output terminal of the logic circuit. A displacement transducer designed to obtain 2. The displacement transducer according to claim 1, which uses any one of a Colpitts-type oscillator, a Hartle-type oscillator, and a Clapp-type oscillator as an oscillator. 3 A first reactance and a second reactance that are placed in the same environment and only one of which changes in response to mechanical displacement, or both of which change differentially, or the first reactance and the second reactance. an oscillator which is alternately switched and connected by a first changeover switch to constitute a resonant circuit; an up/down counter having an addition terminal and a subtraction terminal;
The first changeover switch is connected between the output terminal of the oscillator and the input terminal of the up/down counter, and when the first changeover switch connects the first reactance to the resonant circuit, the output terminal of the oscillator is connected to the addition terminal of the counter. Connect said second
a second changeover switch that operates in synchronization with the first changeover switch so as to connect the output terminal of the oscillator to the subtraction terminal of the counter when the reactance of the up-down counter is connected to the resonant circuit; When the counted value reaches a preset upper limit value, the second changeover switch switches to the subtraction terminal side of the up/down counter, and when the lower limit value reaches the lower limit value, the second changeover switch switches to the subtraction terminal side of the up/down counter. A logic circuit that controls the first and second changeover switches so that the switches are switched to the addition terminal side of the up/down counter, and a pulse width signal and a standard frequency signal from this logic circuit are input, and the period of the pulse width signal is input. control means for controlling the values of other resonant elements constituting the resonant circuit so that the period coincides with the period of the standard frequency signal, and the period from the output terminal of the logic circuit is constant and constant with the mechanical displacement. A displacement transducer that obtains a pulse width signal with a pulse width ratio that has a relationship.