JPS6025579Y2 - capacitive electrical signal converter - Google Patents

Description

[Detailed description of the invention] The present invention relates to a capacitive electrical signal converter that converts the capacitance of a capacitor into an electrical signal.The purpose is to obtain a pulse number corresponding to the ratio of the capacitance of two capacitors with a simple configuration. The aim is to realize a capacitive electrical signal converter that can be used.

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

In the figure, reference numeral 1 denotes a pulse generator, which generates a pulse voltage CP having a constant amplitude E and period ET as shown in FIG. 2A.

2 and 3 are capacitors, and their capacities are C□,
It is C2.

4 and 5 are switches, which are turned on and off in synchronization with the pulse voltage CP with a phase shift of 1800 degrees from each other, as shown in Figure 2, Figure 8. Semiconductor switches such as diodes and field effect transistors are suitable. .

A switch 4 is provided between capacitors 2 and 3.

Reference numeral 6 denotes a buffer amplifier, which is composed of an operational amplifier OP.

The connection point between the capacitor 3 and the switch 4 is connected to the non-inverting input terminal (+) of OP via the resistor 7, and the inverting input terminal (
-) is connected to the output of OP.

Further, the output of OP is connected to the connection point of capacitor 2 and switch 4 via switch 5.

A counting circuit 8 monitors the output Vo of the buffer amplifier 6 and counts the number of pulses from the pulse generator 1 until VO reaches the amplitude E of the pulse voltage CP.

In the present invention configured as described above, when the pulse voltage CP from the pulse generator 1 is on, the switch 4 is turned on and the switch 5 is turned off, and the pulse voltage CP is divided by the capacitors 2 and 3, and the pulse voltage CP is divided by the capacitors 2 and 3. □.

1+. 2E is taken out via the buffer amplifier 6 as the output voltage Vo.

When the pulse voltage CP turns off, the switch 4 turns off, the switch 5 turns on, and the capacitor 3 outputs Vo.
is held, and at the same time capacitor 2 is charged with output Vo.

Next, the pulse voltage CP is turned on, and switch 4 is turned on.
When the switch 5 is turned off, the capacitors 1 to 3 have a hold voltage c1+c2E, a pulse voltage CP1, and a pulse voltage 01. Voltage divided by C2.

1+o2E is superimposed.

That is, the terminal voltage of the capacitor 3 is 2=q- higher.

In this way, until the terminal voltage of the capacitor 3C1+02 becomes equal to the amplitude E of the pulse voltage CP, it continues to increase in steps of CsE for each pulse as shown in FIG. Then, it is given by the following formula.

The counting circuit 8 monitors the output VO of the buffer amplifier 6 and counts the number of pulses from the pulse generator 1 until V reaches E.

Therefore, the counted number of pulses n is as follows, which corresponds to the ratio of the capacitances C□ and C2 of the capacitors 2 and 3.

Therefore, if the capacitance C1 of capacitor 2 is constant,
The number of pulses n corresponds to the capacitance C2 of the capacitor 3.

Also, if the capacitance C2 of the capacitor 3 is constant, the number of pulses n
corresponds to the reciprocal of the capacitance of the capacitor 2, so if the capacitor 2 is made up of a fixed electrode and a movable electrode placed opposite to the fixed electrode and displaced according to the measured quantity such as pressure, differential pressure, etc., the number of pulses can be reduced. n corresponds to the amount of displacement of the movable electrode, that is, the amount to be measured.

As explained above, in this invention, two
A capacitive electrical signal converter is obtained that can directly convert the ratio of the capacitances of two capacitors into the number of pulses.

[Brief explanation of drawings]

FIG. 1 is a connection diagram showing one embodiment of the converter of the present invention, and FIG. 2 is a waveform diagram for explaining its operation. 1... Pulse generator, 2, 3... Capacitor, 4.5... Switch, 6...
Buffer amplifier, 7... Resistor, 8...
Counting circuit.

Claims (1)

[Scope of utility model registration request] means for connecting the first capacitor, the first switch, and the second capacitor in series to the pulse generator; a buffer amplifier for taking out the terminal voltage of the second capacitor; and a means for connecting the output of the buffer amplifier to the second switch. means for connecting the first capacitor and the first switch to the junction point of the first capacitor and the first switch via a
゜It comprises means for turning on and off with a phase shift, and means for monitoring the output of the buffer amplifier and counting the number of pulses from the pulse generator until the output reaches the amplitude of the pulse voltage. Capacitive electrical signal converter.