JPS63133001A - Signal processing method and apparatus for inductance type displacement detector - Google Patents

Abstract

PURPOSE:To obtain a DC signal without ripple, by sampling and holding an output signal near the peak thereof to be converted into a DC signal. CONSTITUTION:An output AC signal C related to the movement of a core 13 and a pulse signal F are applied to a sample holding circuit 60, which samples the signal C when the signal F is ON and otherwise holds it. In other words, as the signal C varies synchronizing with a signal A as input signal, the signal F is turned ON in the vicinity of the peak of the signal C. This allows the detection of the level of voltage only in the vicinity of the peak of the signal C thereby converting the signal C into a DC signal G with no ripple. Thus, the position of the core 13 is detected from the voltage of the signal G.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a signal processing method and apparatus for an inductance displacement detector.

Prior art and its problems Inductance displacement detectors, particularly differential transformers, are widely known as displacement detectors that are cheaper and more reliable than conventional ones. This utilizes the change in inductance of the coil that changes with the mechanical displacement of the core, and converts the mechanical displacement into an electrical signal.

Here, the principle of a conventionally known inductance type displacement detector will be explained with reference to FIGS. 3 to 5.

FIG. 3 shows the principle of a differential transformer, which consists of a primary coil 1, a secondary coil 3.4, and coils 1, 3.
The core 2 is made of a ferromagnetic material and is movably inserted into the core 4. - When a constant AC voltage Ep is applied to the secondary coil 1, the magnetic flux generated thereby is
AC voltages Esl and Es2 are induced, respectively. When the core 2 is in the center position, AC voltages of the same amplitude are induced in the secondary coils 3 and 4, and when the secondary coils 3 and 4 are connected differentially as shown in the drawing, the output voltage Es becomes zero. Becomes a bolt.

This state is illustrated in FIG. 5. As mentioned above, if the core 2 is in the center position, Es=O, and if the core 2 moves from the center position, the output AC voltage Es will be proportional to the amount of movement.
The amplitude of changes. When the core 2 moves from the center position in the opposite direction to the above, the amplitude of the alternating current voltage Es whose phase differs by 180 degrees changes in proportion to the amount of movement. In this way, the mechanical displacement of the core 2 is converted into an electrical signal.

Figure 4 shows another example of an inductance displacement detector,
A constant AC voltage Ep is applied to the coil 5, and the voltage Es between the central portion 6 of the coil 5 and the center voltage of the AC voltage Ep is measured. In the illustrated case, if Ep is an alternating current voltage that swings around zero volts, Es is the voltage between zero volts and the center portion 6 of the coil 5.

In FIG. 4 as well, if the core 7 moves, the result as shown in FIG. 5 can be obtained as in the example of FIG. 3.

That is, if the core 7 is in the center position, the inductance of the upper half and the lower half of the coil 5 are equal, resulting in Es-0.

When the core 7 moves from the center position, the upper half of the coil 5,
A difference occurs in the inductance of the lower half, and Es changes as shown in FIG.

Now, as described above, the mechanical displacement of the core is expressed as an electrical signal,
In particular, it can be measured as a change in an alternating current signal, but it is not practical to see it as a change in an alternating current signal, and conventionally the obtained alternating current signal is converted to a direct current signal by detection and rectification. In this case, as is well known, rectification alone can only obtain a DC signal with large ripples, so it is necessary to remove ripples with a smoothing circuit.

Generally, when a smoothing circuit is provided to make the ripple suitable for practical use, the response frequency of the displacement detector decreases to about 171 O, which is the frequency of the AC voltage Ep applied to the primary coil, resulting in a deterioration of the response. For this reason, in order to improve responsiveness, a method is adopted in which the AC voltage Ep applied to the secondary coil is increased. However, this method handles higher frequencies, which increases current consumption and requires the use of electrical components that can handle high speeds, leading to an increase in price. Additionally, when high-frequency AC voltage is transmitted through the cable that connects the displacement detector and the signal processing circuit, the AC voltage is attenuated and the voltage waveform is distorted due to the stray capacitance of the cable, which limits the length of the cable. There is a disadvantage that it occurs.

Purpose of the Invention The present invention has been made in view of such conventional problems.
The object is to provide a signal processing method and apparatus for a highly responsive inductance displacement detector that can convert an output AC signal into a ripple-free DC signal without rectifying or smoothing it.

Structure of the Invention In order to achieve the above object, the first invention, a signal processing method, converts the mechanical displacement into an electrical signal by utilizing the change in inductance of the coil that changes with the mechanical displacement of the core. In the inductance displacement detector, the steps include inputting a constant alternating current signal A to a coil to obtain an output alternating current signal C, obtaining a pulse signal F that turns on near the peak of the input alternating current signal A, and the above output alternating current signal. The method further includes the step of sampling C when the pulse signal F turns ON, holding it for another time, and converting it into a DC signal G having a signal height near the peak of the output AC signal C. A signal processing device according to a second invention is an inductance displacement detector that converts the mechanical displacement into an electrical signal by using a change in inductance of a coil that changes with the mechanical displacement of a core. an oscillation circuit that generates a constant alternating current signal A input to the coil and an alternating current signal B of the same period whose phase is delayed by 90 degrees from the alternating current signal; A pulsing circuit obtains a pulse signal F, and samples the output AC signal C of the displacement detector when the pulse signal F turns ON, holds it at other times, and calculates the signal height near the peak of the output AC signal C. It has a sample and hold circuit that converts the DC signal G into a DC signal G having a certain value.

DESCRIPTION OF EMBODIMENTS FIG. 1 is a circuit diagram of a signal processing device for an inductance displacement detector according to the present invention, and FIG. 2 is a signal waveform diagram of each part of FIG. 1.

In the figure, 10 is an inductance displacement detector, 20
40 is an oscillation circuit, 40 is an amplifier circuit, 50 is a pulse generator circuit, 6
0 is a sample and hold circuit. In this embodiment, the example shown in FIG. 4 is shown as the displacement detector 10, but the differential transformer shown in FIG. 3 or other inductance type displacement detector may also be used.

The oscillation circuit 20 is a known quadrature oscillation circuit, and includes resistors 21 to 27, capacitors 28, 29, 30, diodes 31, 32, and amplifiers 33, 34. It generates a cosine wave-like voltage signal whose phase is delayed by 90 degrees. These voltage waveforms A
, B are shown in FIG. The oscillation frequency is resistor 21
, 22.23 and capacitors 2B and 29.30.

The power of the sinusoidal voltage A is increased by the amplifier circuit 40 and input to the coil 11 of the displacement detector 10. The amplifier circuit 40 is composed of resistors 41 to 44 and two phase-inverting amplifiers 45 and 46, and the voltage at both ends of the coil 11 is centered at zero volts.
An alternating voltage that oscillates in positive and negative directions is applied.

A voltage waveform between the center portion 12 of the coil 11 and zero volts is obtained by moving the core 13 as shown in FIG. 2C. Among waveforms C, waveform a is different from waveform a when the core 13 moves more than the center position, waveform C is when the core 13 moves closer to the center position than waveform a, and waveform C is different from waveform a when the core 13 moves past the center position. This is the case when moving to the opposite side.

The cosine wave-like voltage signal B is applied to the positive input of the comparator 51 of the pulsing circuit 50, and the negative input is grounded, so the output of the comparator 51 becomes a rectangular wave like D. The signal E is further differentiated into a signal E by a resistor 52 and a capacitor 53, and this differentiated signal E is applied to the positive input of the next comparator 54. Since the constant voltage Vs is applied to the negative input of the comparator 54, the output of the comparator 54 becomes a pulse like F. That is,
Pulse signal F turns ON when voltage signal B exceeds zero volts.
In other words, it turns on near the peak of the voltage signal A. In addition, in the present invention, when the pulse signal F turns ON, it means that the pulse signal F changes from the first state to the second state, for example, a high level and a low level, "1".
It can also be replaced with a change of "0".

The output AC signal C related to the movement of the core 13 and the above-mentioned pulse signal F are applied to a known sample-and-hold circuit 60, and the sample-and-hold circuit 60 converts the C signal and the F signal into
Sample when , and hold at other times. In other words, since the C signal changes in synchronization with the A signal, which is the input signal, the F signal turns ON near the peak of the C signal, and as a result, only the voltage height near the peak of the C signal is detected. It can be converted into a DC signal G with no ripples at all. The voltage a'' of the signal G corresponds to the waveform a of the signal C, the voltage b' corresponds to the waveform A, and the voltage C' corresponds to the waveform C. The position of the core 13 can be detected.

As described above, since a rectifier circuit and a smoothing circuit for removing ripples as in the conventional example are not required, the circuit configuration is much simpler than the conventional example, and the responsiveness is high. As for the expected response, as is clear from the sampling theorem, the response frequency will be up to 172 of the frequency of the AC voltage applied to the coil 11, and there will be no deterioration in response such as 1 no 10 or less as in the conventional case. do not have. Additionally, since a smoothing circuit is no longer required, there is no need to particularly increase the frequency of the AC voltage applied to the coil 11, resulting in an increase in current consumption, an increase in the price of electrical components, and a reduction in the frequency between the displacement detector and the signal processing circuit. Conventional problems such as AC voltage attenuation due to connected cables, waveform distortion, and cable length limitations can be solved all at once.

In the above embodiment, a quadrature oscillation circuit is shown as the oscillation circuit, but other oscillation circuits such as a Wien bridge circuit may be used. However, in the case of a quadrature oscillation circuit, it is possible to simultaneously generate a constant AC signal A and an AC signal B whose phase is delayed by 90 degrees from this AC signal, so it is easy to obtain a pulse signal F near the peak, and the circuit This has the advantage of simplifying the configuration.

Effects of the Invention As is clear from the above explanation, according to the method of the present invention, the output signal of the displacement detector is not rectified and smoothed, but is converted into a DC signal by sampling and holding the vicinity of the peak of the output signal. As a result, there is no ripple at all, high responsiveness is obtained, and there is no need to particularly increase the frequency of the input signal, so various problems associated with increasing the frequency as in the prior art can be solved.

Further, according to the device of the present invention, an oscillation circuit that generates an input signal and another signal whose phase is delayed by 90 degrees from this input signal, and an oscillation circuit that generates an input signal from this other signal near the peak of the input signal (same as the output signal). It is composed of a pulsing circuit that obtains a pulse signal that turns ON, and a sample-hold circuit that obtains a DC signal with a signal height near the peak of the output signal from this pulse signal and the output signal, so it has a simple circuit configuration. It can be easily converted to a ripple-free DC signal.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an example of a signal processing device for an inductance type displacement detector according to the present invention, Fig. 2 is a voltage signal waveform diagram of each part of Fig. 1, and Figs. The principle diagram of the displacement detector and FIG. 5 are its characteristic diagrams. 10... Displacement detector, 11... Coil, 13...
Core, 20...Oscillation circuit, 40...Amplification circuit, 50
...Pulse circuit, 60...Sample and hold circuit. Applicant Sankyo Boeki Co., Ltd. Agent Patent Attorney Hidetaka Tsutsui Figure 2 Figure 3 Figure 4 Figure 5 Core details 1

Claims (2)

[Claims] (1) In an inductance displacement detector that converts the mechanical displacement into an electrical signal by utilizing changes in the inductance of the coil that change with the mechanical displacement of the core, a constant AC signal A is input to the coil and output. A step of obtaining an AC signal C, a step of obtaining a pulse signal F that turns ON near the peak of the input AC signal A, and sampling the output AC signal C when the pulse signal F turns ON and holds the other times. and converting the output AC signal C into a DC signal G having a signal height near the peak. (2) In an inductance displacement detector that converts the mechanical displacement into an electrical signal by utilizing changes in the inductance of the coil that change with the mechanical displacement of the core, a constant alternating current that is input to the coil of the displacement detector An oscillation circuit that generates a signal A and an alternating current signal B having the same period whose phase is delayed by 90 degrees from the alternating current signal A, and pulsing that obtains a pulse signal F that turns on near the peak of the alternating current signal A from the alternating current signal B. The circuit and the output AC signal C of the displacement detector are connected to the pulse signal F.
Sample when it becomes N, hold at other times,
A signal processing device comprising a sample and hold circuit that converts an output AC signal C into a DC signal G having a signal height near the peak.