JP3111352B2 - Hold circuit without periodic disturbance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing disturbance of an output signal of a sensor that outputs a secondary voltage proportional to a displacement amount by supplying a primary voltage.

[0002]

2. Description of the Related Art In a sensor that outputs a secondary voltage proportional to a displacement amount by supplying a primary voltage, a secondary output signal fluctuates in synchronization with an excitation voltage. When the sensor is excited by a pulse signal, the spike signal overlaps the output signal with the excitation. Usually these fluctuations are
It is smoothed by an electronic circuit composed of resistors, diodes, and capacitors. Frequent excitation of the sensor can reduce the amplitude fluctuation of the output signal, and can also speed up the response of the output signal. However, as the number of excitation increases, the current consumption increases and the frequency of spike-like signals increases. These disturbances superimposed on the output signal cause the measurement results to be disturbed when processed by an A / D converter or the like. If the time constant of the smoothing is increased, the amplitude of these disturbances can be reduced, but the response of the output signal becomes slow and the output impedance increases.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a sensor for outputting a secondary voltage proportional to the amount of displacement by supplying a primary voltage. It is related to few electronic circuits.

[0004]

In a sensor that outputs a secondary voltage proportional to a displacement amount by supplying a primary voltage, an analog switch is controlled by a signal synchronized with the excitation signal while exciting the sensor. With this analog switch, a stable output signal without disturbance due to sensor excitation is connected to the hold circuit, and after the output signal is input, the signal is immediately disconnected from the hold circuit. The current consumption is reduced by reducing the number of excitations of the sensor, and the held signal without disturbance is output to the outside with reduced impedance.

[0005]

FIG. 1 shows an embodiment according to the present invention. The sensor 101 is excited by an excitation circuit 102,
The output signal 103 is smoothed by a filter 104 composed of a resistor, a diode, and a capacitor. Spike-like signal 105 and ripple 106 due to smoothing
Reduce the effect of. FIG. 2 shows the relationship between the excitation of 101 and the fluctuation of the signal via 104. The synchronization signal 107 synchronized with the excitation signal is extracted from the
Delay through. The analog switch 109 is controlled by the delayed signal, and the signal via 104 is connected to the hold circuit 110 when the disturbance caused by 105 overlapping the signal via 104 is eliminated. The timing for operating the switches is shown in the lower part of FIG. After inputting the signal via 104 to 110, the control via 109 is promptly stopped to cut off the signal via 104, and the disturbance by 105 causes 11
The output signal 111 of 0 is not disturbed. On the other hand, 1
The signal via 04 attenuates at a constant rate. Therefore, the influence of the output signal 106 of the 110 can be avoided by controlling the 109 and inputting the signal via the 104 to the 110 after a predetermined time has elapsed after exciting the sensor. If the power supply of the hold circuit and the power supply of the sensor excitation circuit are separated and the disturbance overlapping the power supply circuit is avoided, more accurate measurement can be performed.

In the embodiment shown in FIG.
Each time the signal is excited, the signal via the filter 104 is held. In the embodiment of FIG. 3, the signal via the 104 is held after the excitation of the signal 101 a plurality of times. According to this method, the sensitivity of 101 is improved, and even when 101 is rapidly displaced, an output signal corresponding to the displacement can be obtained. If the hold signal 112 indicating that the hold has been completed is transmitted to the external device in synchronization with 109 immediately after holding the signal via 104,
A / D conversion or the like can be performed on the basis of No. 12, and a sampling value synchronized with the excitation of the sensor can be obtained.

The embodiment shown in FIG. 4 is obtained by adding a control signal 113 from an external device to the embodiment shown in FIG. Normally, the state of the sleeve is kept without exciting the 101 to reduce the power consumption of the circuit. 11 from external equipment
When 3 is input, the excitation of 101 is performed a plurality of times as in the embodiment of FIG. 3, and the analog switch 109 is operated at a time when the signal via 104 is stabilized, and the signal via 104 is sent to the hold circuit 110. Connecting. The output impedance of the signal by 110 is small and free from disturbances. Therefore, external devices can process signals without smoothing them with a filter circuit. After processing this signal, 113
To set the excitation circuit 102 into a sleeve state to reduce the power consumption of 101. In the embodiment shown in FIG. 4, the power consumption of the entire circuit including the sensor is turned on during the measurement time, and the power is turned off after the measurement is completed. This is an application that requires intermittent measurement.

In the embodiment shown in FIG. 5, a set of excitation circuits 1
02 and a filter 10 for smoothing the output signal 103
4 is a method for processing 103 by a plurality of sensors 101. In this embodiment, a plurality of analog switches 1
14 is used to excite a plurality of 101 and control 103 in a time-sharing manner to connect to a plurality of hold circuits 110. For simplicity, 101, 102, 104, 11
0 and 114 are described. In this embodiment, 102
It is suitable for applications that use a large number of sensors in a small space because they share the same and 104. Moreover, the same excitation circuit 1
By using the filter 104 for smoothing the signal, the effects of drift due to temperature and fluctuations in the power supply voltage are the same in all sensors, and these effects are canceled out, and the measurement accuracy is improved. Although not shown, the processing based on the time division shown in FIG. 5 can be started by the control signal 113 from an external device to excite a plurality of sensors and hold the output signals.

[0009]

According to the present invention, the output impedance of the sensor is low, so that even if the signal cable becomes long, it is not affected by the induction. Therefore, the signal from the sensor can be processed at a point away from the sensor. Moreover, there is no disturbance or ripple due to excitation, and there is no need to provide a buffer amplifier and a filter circuit for the A / D converter. Further, according to the present invention, it is not necessary to continuously excite the sensor unlike the related art, and an output signal with less disturbance can be obtained even when the number of times of excitation is reduced by intermittent use. If the number of excitations of the sensor is small, power consumption can be reduced, and long-term observation using a battery as a power source can be performed.

When the power consumption of the sensor is large, the sensor and the exciting circuit generate heat, the metal fixing the sensor is deformed, and the electronic circuit drifts. For this reason, the measured values were not stable without time. However, with the sensor according to the present invention, the output signal is not affected by heat generation. In addition, one set of the excitation circuit and the smoothing circuit are shared.
The output signal can be held by multiple sensors, and the drift of the excitation circuit and the smoothing circuit can be offset, which improves the measurement accuracy.

[Brief description of the drawings]

FIG. 1 shows an embodiment according to the present invention.

FIG. 2 is a timing chart of sensor excitation and output signal hold.

FIG. 3 is an embodiment according to the present invention in which excitation is performed a plurality of times at short intervals to increase the response speed.

FIG. 4 shows an embodiment according to the present invention which can be controlled by an external device.

FIG. 5 shows an embodiment according to the present invention for controlling a plurality of sensors in a time-division manner.

Claims (4)

(57) [Claims] In the processing of a smoothed output signal of a sensor in which a secondary voltage corresponding to a displacement amount is output by periodic supply of a primary voltage, (a) an analog signal is generated by a signal synchronized with an excitation signal of the sensor. A hold circuit free from periodic disturbance, comprising: means for controlling a switch to connect and disconnect an output signal; and (b) means for holding an output signal connected by an analog switch. 2. The holding circuit according to claim 1, further comprising means for transmitting to the outside that the output signal of the sensor has been held. 3. An apparatus according to claim 1, wherein the excitation circuit and the signal smoothing circuit are time-shared by a plurality of sensors.
3. A hold circuit which does not include a periodic disturbance according to claim 2. 4. A periodic disturbance, wherein an IC is used as a means for holding a smoothed output signal according to claim 1, and the output impedance thereof is reduced. No hold circuit.