JPH08219704A - Displacement detector - Google Patents

Abstract

PURPOSE: To simplify a circuit and also to obtain a detector with high measurement accuracy by controlling a D/A-converter with a control signal from a microprocessor to apply voltage to a differential transformer and converting it into a digital value for calculation. CONSTITUTION: A D/A-converter 11 is controlled with a control signal 13 from a microprocessor 12 to apply voltage to a primary coil 4 of a differential transformer 3, an output of a secondary coil 5 is amplified when needed, and it is converted into a digital value by an A/D-converter 9 to perform calculation for obtaining measurement results 15. Since a change in the voltage applied to the primary coil 4 can be correctly controlled by the microprocessor 12, A/D-conversion 9 is performed to obtain digital values a programmed number of times at a programmed time while the voltage applied to the primary coil 4 is intermittently varied with predetermined periods. These digital values are smoothed by calculation 14 and a value proportional to a change in outputs from the secondary coil 5 is calculated, thereby obtaining highly accurate measurement results 15.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement detecting device which operates with low current consumption.

2. Description of the Related Art When a displacement amount is detected using a differential transformer or the like, conventionally, as shown in FIG. 1, an electronic circuit 1 creates a sine wave or the like 2 as a primary voltage, and 2 is a sensor. In addition to the primary coil 4 of the differential transformer 3, the output voltage of the secondary coil 5 proportional to the amount of displacement is amplified, rectified 6, converted into a DC voltage by phase detection 7, etc., and passed through a filter 8 to an A / D converter 9. The displacement amount 10 was obtained by guiding and performing A / D conversion.

In the conventional method as described above, the circuit having the functions of 1, 2, 6, 7 and 8 for creating 2 has a large number of parts and has a high probability of failure. The measurement accuracy was poor due to the disturbance of the signal generated at. In addition, because it operates all the time, it consumes a large amount of current, and it was possible to perform measurement only in the range in which the measured displacement and the secondary voltage of the sensor were proportional, and the area occupied by the circuit on the printed circuit board was large, and the circuit was large. There were drawbacks such as difficulty in adjusting. An object of the present invention is to provide a displacement detection device with high measurement accuracy, which has a simplified circuit, as in the embodiment shown in FIG. Therefore, D / A that applies a primary voltage to the sensor 3
The converter 11 and the A / D converter 9 for processing the output signal are intermittently controlled by the control signal 13 by the microprocessor 12.

According to the present invention, in order to achieve the above object, as in the embodiment shown in FIG.
Output 3 and control 11 to apply voltage to 4 and 5 if necessary.
The output of is amplified, converted to a digital value at 9, and a highly accurate measurement result 15 is obtained by calculation 14.

[Operation / Effect / Embodiment] Referring to FIG. 2 showing an embodiment,
Since the change of the voltage applied to 4 can be accurately controlled by 12, the A / D can be programmed 9 times at the programmed time according to the control of 12 while intermittently changing the voltage applied to 4 at a constant cycle. By performing conversion, obtaining digital values, smoothing these digital values at 14, and calculating a value proportional to the output change of 5, it is possible to obtain 15 corresponding to 6 performed by the conventional method. it can. Drawing 3 is 1
A / D of the signal output from 5 in the vertical line during the cycle
This is an example of performing conversion and calculating the arithmetic mean of the converted values. According to this method, 1) the output signal of 5 is directly A / D converted at 9,
There is no error generated in the 7 and 8 circuits, and the measurement accuracy is improved. 2) As shown in the timing chart of FIG. 3, if the number of A / D conversions performed in the unit cycle of the voltage change applied to 4 is increased, 14 improves the measurement accuracy. On the other hand, since the output of 5 changes with a fixed time delay from the change of the voltage applied to 4 which can be controlled by 12, the digital value obtained by performing A / D conversion while controlling the timing several times, As shown in FIG. 4, if 12 is used to correspond to the phase of the change in 4 and smoothing is individually performed and the result is obtained in 14, 15 corresponding to 7 in the conventional case can be obtained. Drawing 4 is 4
The arithmetic mean A of the A / D converted values performed from time 0 to t1 of one cycle of the voltage change applied to
From the arithmetic average B of the A / D converted values performed up to the point, the average value C = (A + B) / 2 of the signal is obtained, and C-A and C-B are added to 9 and corresponding to each phase from 13 timings. , This is an example of obtaining the magnitude of the signal output from 5, including the negative sign, by taking the difference between the two. Also in this method, the signal output from 5 is directly A / D converted, so that the measurement accuracy is improved for the same reason as described above. According to the method shown in the present invention, it is possible to control 2 added to 4 by 12 and 11, so that a waveform suitable for the characteristic of 1 can be added to 4, and when the amplitude of the output signal of 5 is large, Output 9
It is possible to select the time by 12 so that it is digitized, and if the number of A / D conversions performed within the period in which the voltage applied to 4 changes is increased, it is possible to obtain 15 with high accuracy without using 8 or the like. There is an effect that can be obtained. On the other hand, as shown in FIG. 5, a transistor or the like is controlled by 12 without passing through 11, and a voltage is applied to 4 in a pulsed manner only for a short time so that the output of 5 is A / D
Even if the conversion is performed, the response reachability is high in the parts constituting the device such as 9 and 12, so that 15 is obtained in the same manner as described in FIG. If the circuit is controlled so that it operates intermittently as in this example, a measuring device with less current consumption can be created. In the example of FIG. 5, the output level of the virtual signal is shown by a solid line, the time when the voltage is applied in a pulse to 4 is shown by a black vertical line, and the time when the output of 5 is A / D converted is shown by a white vertical line. Even if there are a plurality of sensor outputs, if signals are sequentially A / D converted using a multiplexer, displacements can be detected in parallel by a plurality of sensors in the same manner as described in FIGS. 2 to 5 above. By amplifying the output of 5, a highly sensitive detector can be created. Further, according to the present invention, since the result of A / D conversion can be converted into a displacement amount by calculation, the secondary voltage output as a signal from the sensor does not necessarily have to be proportional to the displacement amount. The dynamic range of can be widened, and if it is a sensor that outputs not only the differential transformer but also the secondary voltage corresponding to the displacement amount by the supply of the primary voltage, it can be used for displacement detection.

[Brief description of drawings]

FIG. 1 Example showing a conventional measurement method

FIG. 2 Example of the present invention

FIG. 3 is an example of a timing diagram of the present invention.

FIG. 4 is an example of a timing diagram of the present invention.

FIG. 5 is a timing chart when the circuit is operated intermittently.

[Explanation of symbols]

1 ………… Electronic circuit, 2 ………… Sine wave, 3
……… Differential transformer 4 ……… Primary coil, 5 ……… Secondary coil,
6 ……… Rectification 7 ……… Phase detection, 8 ……… Filter 9 ……… A / D converter 10 ……… Displacement 11 ……… D / A converter, 12 ……… Microprocessor, 13 ……… Control signal, 14 ……
… Calculation, 15 ……… Measurement result

Claims (1)

[Claims] 1. In a displacement detection device using a sensor that outputs a secondary voltage corresponding to a displacement amount by supplying a primary voltage, a microprocessor controls the primary voltage applied to the sensor, and synchronizes with the change. Displacement detection device characterized by performing A / D conversion of an output secondary voltage, obtaining a displacement amount by calculation of a digital value obtained as a result of the A / D conversion, and operating with low current consumption