JPH07311006A - Differential transformer - Google Patents

Abstract

PURPOSE:To provide a differential transformer which dose not allow any measurement error to be led even if there exists dislocation in phase between the wave form of the output of a primary coil and the wave form of the output of each secondary coil. CONSTITUTION:In a differential transformer 10 measuring displacement with its probe 14 brought into contact with a measured object 12, the aforesaid transformer is equipped with a core 16 which is moved in response to displacement, a primary coil 18 and with secondary coils 20 and 22. AC voltage is inputted to the primary coil 18 with both its voltage and frequency kept constant, and electro motive force is produced in the secondary coils 20 and 22 as the core 16 is moved. Voltage outputted from the secondary coil 20 is operated as specified, it is inputted into a rectifying circuit 30 thereafter, and it is then chopped on the basis of the voltage of an addition circuit 28 so as to be rectified. Since there is no dislocation in phase between objective voltage for rectifying and chopper voltage, no error appears in DC voltage which is rectified after it has been chopped. By this constitution, no measurement error thereby appears for the displacement of a measured object.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential transformer, and more particularly to a differential transformer which eliminates a measurement error due to a phase shift between a waveform of a primary coil output and a waveform of a secondary coil output. .

[0002]

2. Description of the Related Art Differential transformers are widely used in measuring devices for electrically measuring displacement of an object to be measured.
As shown in FIG. 5, in the conventional differential transformer 2, the voltage output from the secondary coil in accordance with the movement of the core 4 at the time of measurement in a state where the voltage of a constant frequency is applied to the primary coil. After that, a predetermined calculation was performed, and then the calculated voltage was rectified in the rectifier circuit 6 using the voltage of the primary coil as a reference waveform and used as the measured value.

[0003]

However, as shown in FIG.
As shown in (f), the phase of the voltage waveform output from the secondary coil deviates from the phase of the voltage waveform output from the primary coil due to the movement of the core 4. 6 (g), and the phase difference between the voltage waveform of the primary side coil output and the voltage waveform of the secondary side coil output increases or decreases depending on the movement speed of the core 4 and is output. There is a problem that the DC voltage varies and a measurement error occurs.

The present invention has been made in view of the above circumstances. Even if a phase shift occurs between the voltage waveform of the primary coil output and the voltage waveform of the secondary coil output, a measurement error is generated. The purpose is not to generate.

[0005]

In order to achieve the above object, the present invention comprises a primary side coil and a secondary side coil, and in a state where a constant voltage and a constant frequency are applied to the primary side coil. In a differential transformer that measures displacement of an object to be measured based on the secondary coil output generated by moving a core, the secondary coil output is set to a reference waveform with the cycle of the secondary coil output as a reference waveform. It is characterized in that it is rectified and used as a measurement value.

Further, in order to achieve the above object, the present invention is characterized in that the size of the secondary coil output is size-shifted before the rectification with the cycle of the secondary coil output as a reference waveform.

[0007]

According to the present invention, the core is moved in a state where the constant voltage is applied to the primary coil at a constant voltage, and the generated secondary coil output is rectified based on the cycle of the secondary coil output. Used for measurements. Therefore, no error occurs in the measured value. Further, according to the present invention, before the secondary coil output is rectified, the secondary coil output is size-shifted using the cycle of the secondary coil output as a reference waveform and used as a measured value after the rectification. Therefore, no error occurs in the measured value.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a differential transformer according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a differential transformer 10 which is a first embodiment of the present invention. In the figure, 12 is the DUT, 14 is a probe, and 16 is the DUT 1.
It is a core that moves according to the displacement of 2. A primary coil 18 and secondary coils 20, 22 are provided on both sides of the core 16. A constant voltage and a constant frequency AC voltage are input to the primary coil 18 from an oscillator circuit (not shown), and
Electromotive force is generated in the secondary coils 20 and 22 as the core 16 moves. The inverting circuit 24 inverts the voltage output from the secondary coil 20, and then the adder circuit 26 adds the voltages output from the secondary coil 22. On the other hand, the adder circuit 28 adds the voltages output from the secondary coils 20 and 22, and outputs the added voltage to the rectifier circuit 30 as a reference for rectification. The rectifier circuit 30 chops and rectifies the voltage input from the adder circuit 26 with reference to the voltage input from the adder circuit 28.

A method of measuring the displacement of the object 12 to be measured with the differential transformer 10 configured as described above will be described. Probe 14
Is brought into contact with the object to be measured 12, and a switch (not shown) of the differential transformer 10 is turned on. At this time, the primary coil 18 is applied with a constant voltage and a constant frequency as shown in FIG. 2A, for example, an AC voltage of 5V, 4KHz.

If the object to be measured 12 is a little large,
The displacement is transmitted to the core 16 via the probe 14 and is displaced upward. Then, the 1 o'clock side coil 18 and the secondary side coil 2
Since the amount of the core 16 with 0 increases, the induced electromotive force of the secondary coil 20 becomes larger than that before the core 16 moves upward, and conversely, the induced electromotive force of the secondary coil 22 decreases. The displacement of the DUT 12 is indicated based on this output voltage.

The voltage output from the secondary coil 20 (see FIG. 2 (b)) is inverted by the inversion circuit 24, and thereafter,
The addition circuit 26 adds the voltage output from the secondary coil 22 (see FIG. 2C). Voltage after addition (Fig. 2
(See (d)) is output to the rectifier circuit 30. On the other hand, the voltages output from the secondary coil 20 and the secondary coil 22 are added by the adder circuit 28, and the chopper voltage (FIG. 2E) is added.
Refer to the reference voltage. The voltage from the adder circuit 26 input to the rectifier circuit 30 is chopped with the chopper voltage (see FIG. 2 (g)). At this time, the voltage output from the adder circuit 26 and the chopper voltage are synchronized as shown in FIG.
It becomes a regular chevron as shown in (g). Eventually,
The displacement of the DUT 12 is shown based on the DC voltage obtained by rectifying the waveform after the chopping.

Therefore, since the voltage output from the adder circuit 26 (voltage to be rectified) and the chopper voltage are not out of phase with each other, no error occurs in the DC voltage rectified after the chopping. As a result, the measurement error of the displacement of the DUT 12 does not occur. In addition, in the above-mentioned embodiment, the case of measuring the vertical fluctuation of the object to be measured with the differential transformer has been described.
The present invention is not limited to this, and any measurement of pressure, deflection, load, etc. may be performed using a differential transformer.

FIG. 3 shows an outline of a differential transformer 40 including a size shift circuit according to a second embodiment of the present invention. In the figure, the same members and circuits as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The second embodiment differs from the first embodiment in FIG. 1 in that a size shift circuit 44 is provided between the adder circuit 26 and the rectifier circuit 30, and the circuit 28 and the rectifier circuit 3 are provided.
That is, the D / A conversion circuit 42 is provided between the D / A conversion circuit 42 and 0. The D / A conversion circuit 42 performs A / D exchange on the output of the rectifier circuit 30 with the voltage input from the circuit 28 as a reference, and C
Digital data is input from the PU, converted from digital to analog, and output to the size shift circuit 44 and the rectifier circuit 30. The voltage output from the adder circuit 26 is amplified by the size shift circuit 44 and output to the rectifier circuit 30.

A method of measuring the displacement of the object 12 to be measured with the differential transformer 40 having the above-described structure will be described. The voltage output from the secondary coil 20 (see FIG. 4B) is inverted by the inversion circuit 24, and then the voltage output from the secondary coil 22 in the adder circuit 26 (FIG. 4C). (See) is added. The added voltage (see FIG. 4D) is output to the size shift circuit 44. On the other hand, the secondary coil 20,
The voltage output from 22 is added by the adder circuit 28, and D
The size shift amount is converted into an analog signal by the / A conversion circuit 42 (see FIG. 4E). The voltage input from the adder circuit 26 to the size shift circuit 44 is size-shifted with reference to the voltage input from the adder circuit 28 (see FIG. 2F) and output to the rectifier circuit 30. In the rectifier circuit 30,
The size-shifted voltage is chopped and rectified based on the voltage input from the D / A conversion circuit 42. During this period, these voltages are synchronized as shown in FIGS. 4 (d) to 4 (h).

Therefore, the voltage output from the adder circuit 26 (the voltage to be size-shifted) and the D / A conversion circuit 4
Since the phase is not shifted from the voltage output from 2 (the voltage that serves as a reference for size shift), an error due to size shift does not occur. Further, since the voltage output from the size shift circuit 44 (the voltage to be rectified) and the chopper voltage are not out of phase with each other, no error occurs in the DC voltage rectified after the chopping. As a result, the measurement error of the displacement of the DUT 12 does not occur.

[0016]

As described above, according to the differential transformer of the present invention, when the secondary coil output is rectified or size-shifted, the secondary coil output is used as a reference, so that the phase is There is no deviation. Therefore, no error occurs in the value after rectification, and no error occurs in the measured value.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a first embodiment of a differential transformer according to the present invention.

FIG. 2 is a voltage waveform diagram of various parts of the differential transformer shown in FIG.

FIG. 3 is a schematic diagram of a second embodiment of a differential transformer according to the present invention.

FIG. 4 is a voltage waveform diagram of various parts of the differential transformer shown in FIG.

FIG. 5 is a schematic diagram of a conventional differential transformer.

6 is a waveform diagram of voltage at various points in the differential transformer shown in FIG.

[Explanation of symbols]

 10, 40 ... Differential transformer 18 ... Primary side coil 20, 22 ... Secondary side coil 30 ... Rectifier circuit 44 ... Size shift circuit

Claims (2)

[Claims] 1. A primary coil and a secondary coil are provided,
A differential transformer that measures displacement of an object to be measured based on the secondary coil output generated by moving a core while applying a constant voltage and a constant frequency to the primary coil, A differential transformer characterized in that the side coil output is rectified using the cycle of the secondary side coil output as a reference waveform and used for a measured value. 2. The differential transformer according to claim 1, wherein the secondary side coil output is size-shifted before the rectification using the cycle of the secondary side coil output as a reference waveform.