JPS5819492Y2 - Piezoelectric sensor tester - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a tester for detecting insulation failure or disconnection in piezoelectric sensors such as vibration pickups, force gauges, pressure pickups, etc.

Generally, piezoelectric sensors have an extremely large internal resistance, so the insulation resistance between the connectors and the electrodes of the piezoelectric element must be sufficiently large.

However, for performance reasons, ordinary piezoelectric sensors have small connectors for extracting output signals and thin lead wires, so most failures of piezoelectric sensors are due to poor insulation or broken lead wires. It is.

In a normal piezoelectric sensor, the internal resistance is 109Q or more,
Many sensors have a capacitance of about 1O-9F, and if the lead wire of such a sensor is broken, the capacitance decreases to about 10-10 to 1O-12F.

Furthermore, in the case of poor insulation, the apparent internal resistance decreases as the insulation deteriorates.

The purpose of this idea is to provide a tester that can simultaneously check the capacitance and internal resistance of a piezoelectric sensor to easily detect disconnections and insulation defects in the sensor. A piezoelectric sensor tester that applies AC voltage, extracts the DC voltage component and AC voltage component from the applied signal voltage, and compares them with predetermined set voltages to detect wire breaks and insulation defects. be.

Next, one embodiment of this invention will be described.

Reference numeral 1 designates an oscillator for generating an alternating current voltage of angular frequency ω and voltage Ew, and reference numeral 2 designates a direct current voltage E provided in parallel with the oscillator 1.

This is a DC power supply for generating.

A capacitor 3 having a capacitance Cs is connected in series to the oscillator 1, a resistor 4 having a resistance value Rs is connected in series to the DC power source 2, and both the resistor 4 and the capacitor 3 are It is connected to apply an AC voltage with a DC voltage component superimposed to the piezoelectric sensor 5 to be tested, which will be described below.

The piezoelectric sensor to be tested has a capacitance Cp and an internal resistance Rp.

The angular frequency ω of the oscillator 1, the capacitance Cs of the capacitor, and the resistance Rs should satisfy the following equation (1), and in a normal piezoelectric sensor, the capacitance Cp is 1O-9F.
It is selected taking into consideration that the internal resistance Rp is 109 g or more.

6 is a low-pass filter that passes only the DC voltage component of the terminal voltage of the piezoelectric sensor 5, and 7 is a high-pass filter that passes only the AC voltage component of the terminal voltage, which is connected in parallel with the low-pass filter 6. These two filters have a sufficiently high input impedance so as not to affect the piezoelectric sensor terminal voltage in the preceding stage.

A comparator 8 is connected in series to the low-pass filter 6, and is configured to compare the DC voltage component that has passed through the low-pass filter 6 with a predetermined set voltage for the comparator 8. A comparator 9 is connected in series to the device 7, and is configured to compare the AC voltage component that has passed through the high-pass filter 7 with a predetermined set voltage for the comparator 9.

Furthermore, an insulation failure indicator 10 is connected to the comparator 8, and a disconnection indicator 11 is connected to the comparator 9.

When testing a piezoelectric sensor using the tester described above, the terminal voltage of the piezoelectric sensor 5 to be tested is as follows under the condition that the piezoelectric sensor satisfies the above formula (1) when the piezoelectric sensor is normal.

If the lead wire is disconnected in the piezoelectric sensor being tested, the value of capacitance Cp will be 1 to 1 compared to when it is normal.
Since the value is two orders of magnitude smaller, it becomes ``Ame >>Umaeki'', and as a result, the AC component becomes larger than normal.

If insulation failure occurs in the piezoelectric sensor, the internal resistance R
This is because p becomes smaller and Rp<RI) no longer holds true, and the DC voltage component is certainly smaller than in normal times.

In the above equation (7), the inequality sign indicates when insulation deterioration has progressed to such an extent that buff 〈p'' no longer holds true.

In order to detect the above-mentioned insulation failure and disconnection, the set voltage of the comparator 8 is set to E in consideration of equations (2), (4), and (6).

Select an appropriate value between 0 and 0, and adjust it so that when the DC voltage component from the piezoelectric sensor 5 becomes less than the set voltage, the indicator 10 will issue an insulation failure display signal, and the comparator 9 For the setting voltage, select an appropriate value between E, , ~E, based on formulas (3), (5), and (7), and make sure that the AC voltage component from the piezoelectric sensor 5 is the set voltage. Adjustment is made so that when the wire breakage exceeds 100 kHz, the display 11 issues a disconnection display signal.

If the set voltage of each comparator is set in this way, when the piezoelectric sensor under test is tested, if there is no disconnection or insulation failure in the sensor, the AC voltage with the DC voltage component superimposed from the oscillator and DC power supply will be Even if a voltage is applied to the piezoelectric sensor, the DC voltage component between the piezoelectric sensor terminals is E.

Since the AC voltage component is approximately, no signal is emitted from the display, but if an insulation failure occurs in the piezoelectric sensor, the DC voltage component will be smaller than in a normal case, so A signal is emitted from the display.

Furthermore, in the case of a wire breakage, the alternating current voltage component becomes larger than the normal value (approximately), so a wire breakage signal is shown on the display via the comparator, making it possible to know that there is a failure in the piezoelectric sensor.

The tester of this invention can reliably detect poor insulation or disconnection of the piezoelectric sensor, and can be used to check whether the sensor is in a normal condition, allowing accurate measurements of the object to be measured. be able to.

Moreover, the circuit configuration of the invented tester itself is simple and the price is relatively low.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of this detector. Explanation of symbols 1 is an oscillator, 2 is a DC power supply, 3 is a capacitor, 4 is a resistor, 5 is a piezoelectric sensor to be tested, 6 is a low-pass filter, 7 is a high-pass filter, 8 and 9 are comparators, 10 .11 is the display.

Claims (1)

[Scope of utility model registration request] a circuit comprising an oscillator for generating an alternating current voltage in order to apply an alternating voltage with a superimposed direct current voltage component to the piezoelectric sensor under test, and a capacitor connected in series to the oscillator;
The terminals of a circuit consisting of a DC power supply provided in parallel with the oscillator and a resistor connected in series with the DC power supply are connected, and the signal voltage applied to the piezoelectric sensor under test from the two circuits is connected to each other. A reduction filter provided to extract the DC voltage component from the inside, a comparator to compare the DC voltage component obtained by the reduction filter with a predetermined set voltage, and a piezoelectric sensor to be tested. A high-pass filter provided to extract the AC voltage component from the applied signal voltage, and a comparator to compare the AC voltage extracted from the high-pass filter with a predetermined set voltage. A piezoelectric sensor tester comprising: a piezoelectric sensor that operates an indicator by a detection signal from the above comparator.