JP2001204175A - Method of increasing resistance of ac-driven electric circuit to external noise, magnetically coupled displacement converter, and capacitor type differential pressure transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the resistance of an AC-driven electric circuit to external noise. SOLUTION: A driving signal Vd made by frequency-modulating an orignal signal of an angular frequency ω1 by means of a modulation signal of an angular frequency ω2 is used. Thereby, the energy of signals of the electric circuit can be distributed into many frequencies, increasing the resistance of the electric circuit to external noise of specified frequencies.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for enhancing external noise immunity of an AC drive electric circuit, a magnetic coupling type displacement converter and a capacitive differential pressure transmitter, and more particularly, to one of final output signals of an electric circuit. Other parts relate to a method and apparatus for enhancing the immunity of a part to external noises while maintaining its purpose and function.

[0002]

2. Description of the Related Art In an AC drive circuit according to the prior art, an electric circuit designed for the purpose of measurement, detection, etc., is driven by an AC of a single frequency and outputs a detection signal of the single frequency. Electrical circuits are well known. For example, a magnetic coupling type displacement converter will be described as an example of an electric circuit which is driven by a single frequency alternating current and outputs a single frequency detection signal.

As shown in FIG. 3, a magnetic coupling type displacement conversion device has a drive signal Vd = V · s having an amplitude V and an angular frequency ω.
an oscillation circuit 1 that outputs inωt, and a displacement conversion circuit 2 that includes a primary coil and a secondary coil that receive the drive signal Vd and detect displacement based on the principle of a differential transformer.
An amplifier 3 for amplifying the dielectric voltage from the displacement conversion circuit 2 with a predetermined amplification factor A; a synchronous rectifier 4 for synchronizing / rectifying the detection signal vs. amplified by the amplifier 3 with a drive signal Vd; And a smoothing circuit 5 for smoothing the rectified signal and outputting a displacement signal.

The displacement conversion circuit 2 has a primary coil 2a and a secondary coil 2b, which are magnetically coupled to each other. The primary coil 2a receives a drive signal V from the oscillation circuit 1.
d is applied to generate a closed magnetic flux, and the secondary coil 2b is installed in the path of the closed magnetic flux generated by the primary coil 2a,
As a result, an induced voltage is generated, and the induced voltage is output from the output terminal. The functional operation of the displacement conversion circuit 2 having such a configuration is a function K of the displacement x of the rotation angle or the movement amount.
(X), the output voltage of the secondary coil 2b is K (x) times the input voltage of the primary coil 2a, that is, K (x) · V
· It is represented by sinωt.

The amplifier 3 generates a detection signal vs which is obtained by amplifying the output signal of the dielectric voltage from the displacement conversion circuit 2 with the amplification factor A, and this detection signal vs is expressed as: vs = A · K (x) · V · sin ωt. The detection signal vs of the amplifier 3 is synchronously rectified by a synchronous rectifier 4 to which a synchronization signal is supplied from the oscillation circuit 1 and then smoothed by a smoothing circuit 5, and is output as a displacement signal indicating a displacement amount.

FIG. 4 shows a frequency spectrum of the detection signal vs. As illustrated, the frequency component of the detection signal vs has only a single angular frequency ω. That is, the total energy of the detection signal vs exists only at the angular frequency ω. This is driven at a single frequency that is the same as the frequency of the extraneous noise,
This is a common problem for all electric circuits that output the single frequency detection signal.

That is, if external noise having an angular frequency ω enters such an electric circuit, 100% of the energy of the output signal is exposed to the external noise. The signal cannot be extracted accurately.

As such external noise, for example,
Common mode noise. These noises
Even if the electric circuit is insulated in a direct current manner, it easily penetrates through capacitive coupling or the like. For this reason, various preventive measures have been conventionally considered to prevent external noise from entering an electric circuit, and have been implemented in design and manufacture.

[0009]

However, in order to prevent noise from entering the electric circuit from the outside as in the above-mentioned conventional countermeasures against noise, it is costly to design, manufacture and maintain the electric circuit. There was a problem.

[0010] Accordingly, the present invention is to solve the above-mentioned problems by accommodating external noise to an electric circuit to some extent, and then improving the resistance of the electric circuit itself to the introduced external noise. An object of the present invention is to provide a method and apparatus for enhancing external noise resistance of a circuit.

[0011]

According to the present invention, there is provided a method for enhancing external noise immunity of an AC drive electric circuit, a magnetic coupling type displacement converter, and a capacitive differential pressure transmitter according to the present invention. It is to be.

(1) An AC drive electric circuit for obtaining a displacement signal by rectifying / smoothing a detection signal vs corresponding to a displacement of an AC drive signal having an angular frequency ω1 in synchronization with the AC drive signal, wherein the angular frequency is The original AC drive signal of ω1 is converted to angular frequency ω2
Drive signal Vd created by frequency modulation with the modulation signal
And the detection signal v dispersed in a plurality of frequencies
A method for enhancing external noise immunity of an AC drive electric circuit, wherein s is generated, and a detection signal vs dispersed in the plurality of frequencies is synchronized with the drive signal Vd to obtain a displacement signal. (2) an AC drive signal generation unit that generates an AC drive signal having the angular frequency ω1, a displacement conversion circuit that detects a displacement of the AC drive signal output from the AC drive signal generation unit,
A circuit for amplifying / rectifying / smoothing the signal detected by the displacement conversion circuit and outputting a displacement signal, wherein the AC drive signal generation unit comprises: A magnetic coupling type displacement converter comprising: an oscillation circuit for generating a drive signal; and frequency modulation means for generating an AC drive signal obtained by frequency-modulating an original AC drive signal of the oscillation circuit with a modulation signal having an angular frequency of ω2. apparatus. (3) A capacitive differential having an AC drive signal generator for generating an AC drive signal having an angular frequency ω1, and a capacitive differential pressure detector driven by the AC drive signal output from the AC drive signal generator. A pressure transmitter, wherein the AC drive signal generator comprises an oscillator circuit for generating an original AC drive signal having an angular frequency ω1, and an AC drive signal obtained by frequency-modulating an output signal of the oscillator circuit with a modulation signal having an angular frequency ω2. And a frequency modulating means for generating a differential pressure.

The energy of the signal of the electric circuit driven by the frequency-modulated drive signal by the method for enhancing the external noise resistance of the AC drive electric circuit having the above configuration is dispersed at a plurality of frequencies. As a result, 100% of the signal
Eliminates the drawbacks of conventional electric circuits that are exposed to extraneous noise of a specific frequency, and the signal energy of that frequency is impaired by the extraneous noise of the specific frequency even if the extraneous noise of the specific frequency impairs the purpose and purpose of the electric circuit. It is possible to realize a so-called noise-resistant electric circuit that performs a function.

In the magnetic coupling type displacement converter having the above configuration, since the drive signal output from the drive signal generator has signal components dispersed in a plurality of frequencies, the displacement signal output from the magnetic coupling type displacement converter is also generated. Similarly, it has signal components dispersed in a plurality of frequencies. Therefore, even if a displacement signal component of a specific frequency is disturbed by noise of a specific frequency, noise resistance can be enhanced by a displacement signal component of another frequency.

In the capacitive differential pressure transmitter having the above configuration, the drive signal output from the drive signal generator has signal components dispersed in a plurality of frequencies, so that the differential pressure signal output from the capacitive differential pressure transmitter is output. Also have signal components dispersed over a plurality of frequencies. Therefore, even if the differential pressure signal component of that frequency is disturbed by noise of a specific frequency, the noise resistance can be enhanced by the differential pressure signal component of another frequency.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a method for enhancing external noise resistance of an AC drive electric circuit, a magnetic coupling type displacement converter and a capacitive differential pressure transmitter according to the present invention. .

FIG. 1 shows a configuration of an embodiment of a magnetic coupling type displacement converter to which a method for enhancing external noise resistance of an AC drive electric circuit according to the present invention is applied.

In FIG. 1, the same reference numerals as those in FIG. 3 described in the prior art denote the same parts. The magnetic coupling type displacement converter shown in FIG. 1 is different from the magnetic coupling type displacement converter shown in FIG. 3 in that the oscillation circuit 1 is connected to a modulation circuit 6 corresponding to a frequency modulating means which is a key point of the present invention. It is. still,
The drive signal generator 10 is formed by the oscillation circuit 1 and the modulation circuit 6.

As shown in FIG. 1, the magnetic coupling type displacement converter having such a configuration has an amplitude V and an angular frequency ω.
1. An oscillation circuit 1 that outputs the original AC drive signal Vd · sin ω1t, and a primary conversion coil and a secondary coil that receive the original AC drive signal and detect the displacement based on the principle of a differential transformer. 2 and this displacement conversion circuit 2
Amplifier 3 which amplifies the dielectric voltage from the circuit with a predetermined amplification factor A
And a synchronous rectifier 4 for synchronizing / rectifying the detection signal vs amplified by the amplifier 3 with the drive signal Vd, a smoothing circuit 5 for smoothing the synchronously rectified signal and outputting a displacement signal, and a oscillating circuit 1. And a modulation circuit 6 for frequency-modulating the output signal.

The displacement conversion circuit 2 has a primary coil 2a and a secondary coil 2b, which are magnetically coupled to each other. The primary coil 2a receives a drive signal V from the oscillation circuit 1.
d to generate a closed magnetic flux, the secondary coil 2b is installed in the path of the closed magnetic flux generated by the primary coil 2a,
As a result, an induced voltage is generated, and the induced voltage is output from the output terminal. The functional operation of the displacement conversion circuit 2 having such a configuration is a function K of the displacement x of the rotation angle or the movement amount.
(X), the output voltage of the secondary coil 2b is K (x) times the input voltage of the primary coil 2a, that is, K (x) · V
It is represented by d · sin ω1t. The amplifier 3 generates a detection signal vs which is obtained by amplifying the output signal of the dielectric voltage from the displacement conversion circuit 2 with the amplification factor A, and this detection signal vs.
Is as follows: vs = A · K (x) · Vd · sin ω1t The detection signal vs of the amplifier 3 is synchronously rectified by a synchronous rectifier 4 to which a synchronization signal is supplied from the oscillation circuit 1, and then smoothed by a smoothing circuit 5, and is output as a displacement signal indicating a displacement amount.

The oscillation circuit 1 outputs a signal (V · sin ω1t) having a voltage amplitude V and an angular frequency ω1. The modulation circuit 6 generates a modulation signal (Vm · sin) having a voltage amplitude Vm and an angular frequency ω2.
ω2t), the output signal of the oscillation circuit 1 is frequency-modulated. As a result, the drive signal Vd is output from the drive signal generator 10 including the oscillation circuit 1 and the modulation circuit 6, and is supplied to the primary coil 2a of the displacement conversion circuit 2.

The maximum angular frequency shift of the drive signal Vd caused by the modulation signal (Vm · sin ω2t) is represented by Δω1,
When the modulation index (Δω1 / ω2) is represented by m, the modulated drive signal Vd is expressed as follows.

[0023]

(Equation 1)

Therefore, the displacement signal v output from the amplifier 3
s is represented as follows.

[0025]

(Equation 2)

FIG. 2 shows the frequency spectrum of the detection signal vs when the modulation index is m = 1.4. This detection signal vs.
Generates a displacement signal which is rectified by the synchronous rectifier 4 and further smoothed by the smoothing circuit 5 to be an output of the magnetic coupling type displacement converter.

As can be seen from the frequency spectrum shown in FIG. 2, the energy of the detection signal vs has a plurality of frequencies, for example, angular frequencies ω1-ω2, ω
1-2ω2, ω1-3ω2, ω1 + ω2, ω1 + 2ω
2, ω1 + 3ω2. In the case where m = 1.4, the angular frequency component ω
Even if an external noise of 1 enters, the energy of the signal component having the angular frequency ω1 is 30.25% of the total energy.
(The amplitude of 0.55 squared), the energy of the detection signal vs exposed to the external noise is 30.25 of the whole.
%. The same can be said for the case where external noise of another frequency enters. In this manner, the external noise of the angular frequency component ω1 is affected by the signal, but the energy of the detection signal is dispersed, so that the frequency components other than the angular frequency component ω1, which is the external noise, are affected. I will not give. Therefore, it is possible to realize a displacement conversion device that is strong against external noise.

Hereinafter, as another embodiment, a capacitive differential pressure transmitter which detects a change in differential pressure from a change in capacitance will be described. The configuration of this capacitive differential pressure transmitter is the same as that shown in FIG. 1 except that the displacement differential circuit 2 is replaced with a capacitive differential pressure detector, and the operation is the same as that of the magnetic coupling type displacement converter. Is omitted.

Although the above embodiments have been described with reference to the two embodiments, the present invention is not limited to these embodiments, and it is needless to say that the present invention can be applied to enhance the external noise resistance of all AC driving electric circuits.

[0030]

As described above, the method for enhancing the external noise immunity of an AC drive electric circuit according to the present invention uses the frequency-modulated and dispersed drive signal in the AC drive electric circuit to output the electric circuit. There is an effect that the energy of the signal is distributed to many frequencies, and as a result, the noise resistance of the electric circuit against a specific external noise can be enhanced.

Therefore, in the design of the electric circuit, a design that is tolerant to the intrusion of external noise can be achieved.
This has the effect of reducing the cost of countermeasures for extraneous noise.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a magnetic coupling type displacement conversion device according to the present invention.

FIG. 2 is an explanatory diagram showing a frequency spectrum of a displacement signal of the magnetic coupling type displacement converter.

FIG. 3 is a block diagram showing a configuration of a magnetic coupling type displacement conversion device according to a conventional technique.

FIG. 4 is an explanatory diagram showing a frequency spectrum of a displacement signal of the magnetic coupling type displacement converter.

[Explanation of symbols]

Reference Signs List 1 oscillation circuit 2 displacement conversion circuit 2a primary coil 2b secondary coil 3 amplifier 4 synchronous rectifier 5 smoothing circuit 6 modulation circuit A amplification degree m modulation index K (x) displacement function V voltage amplitude V _m voltage amplitude ω1 angular frequency ω2 angular frequency Vd drive signal vs. detection signal

Claims (3)

[Claims] 1. An AC drive electric circuit for obtaining a displacement signal by rectifying / smoothing a detection signal vs according to a displacement of an AC drive signal having an angular frequency ω1 in synchronization with the AC drive signal, wherein the angular frequency ω1 Is driven by a drive signal Vd created by frequency-modulating the original AC drive signal of FIG. 1 with a modulation signal of an angular frequency ω2 to generate a detection signal vs dispersed in a plurality of frequencies, and the detection signal vs dispersed in the plurality of frequencies Wherein the displacement signal is obtained in synchronization with the drive signal Vd. 2. An AC drive signal generator for generating an AC drive signal having an angular frequency ω1, a displacement converter for detecting a displacement of the AC drive signal output from the AC drive signal generator, and the displacement converter. And a circuit for amplifying / rectifying / smoothing the signal detected in the step (b) and outputting a displacement signal, wherein the AC drive signal generating unit comprises:
An oscillation circuit for generating an original AC drive signal having an angular frequency ω1,
A frequency-coupling means for generating an AC drive signal obtained by frequency-modulating the original AC drive signal of the oscillation circuit with a modulation signal having an angular frequency of ω2. 3. A capacitor having an AC drive signal generator for generating an AC drive signal having an angular frequency ω1, and a capacitive differential pressure detector driven by the AC drive signal output from the AC drive signal generator. A differential pressure transmitter, wherein the AC drive signal generator includes an oscillation circuit that generates an original AC drive signal having an angular frequency ω1, and an AC circuit that frequency-modulates an output signal of the oscillation circuit with a modulation signal having an angular frequency ω2. And a frequency modulation means for generating a drive signal.