JP2006162338A - Signal processing device of differential transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To acquire an output signal having high response speed by preventing operational delays caused by a low-pass filter. <P>SOLUTION: This signal processing device of a differential transformer for acquiring a measured signal, having high response speed from the differential transformer, is equipped with a first high-speed analog/digital converter 60 for digitizing an output signal from the differential transformer, a second high-speed analog/digital converter 64 for digitizing the drive signal from the differential transformer, and a digital signal processing means (66) for performing synchronous detection of the differential transformer output signal by the drive signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a signal processing apparatus for a differential transformer for obtaining a measurement signal having a high response speed from the differential transformer. In particular, a measurement signal with a response speed of 10 to 100 times (200 Hz to 2 kHz) is obtained using a conventional head having an excitation frequency of about 5 kHz, which is suitable for use in a high-resolution electric micrometer with a resolution of 1 nm class. The present invention relates to a signal processing apparatus for a differential transformer.

  As shown in FIG. 1, a conventional electric micrometer includes a core 26 to which displacement of a spindle 22 constituting a head 20 is transmitted, and a mechanical center position of the core 26 (see FIG. 1). By using a differential transformer including sensor coils 28 and 30 connected in series with each other, provided symmetrically with respect to each other (referred to as a neutral point), the change in impedance of the sensor coils 28 and 30 depending on the position of the core 26 is used. When a voltage is applied to the sensor coils 28 and 30 from the external oscillator 32, the core 26 of the difference between the voltages E1 and E2 (E1-E2) as shown in FIG. The displacement of the spindle 22 was detected on the basis of the change due to the position.

  Specifically, as shown in FIG. 3, for example, a sinusoidal drive signal having a frequency of 5 kHz generated by an oscillator 32 is passed through a drive amplifier 34 to sensor coils 28 and 30 ( (Not shown), the output signal obtained from the neutral point of the sensor coils 28 and 30 is amplified by the preamplifier 36, and the half wave or the whole wave is synchronized with the excitation signal driven by the oscillator 32 by the synchronous detector 38. After rectifying the wave and removing the 5 kHz component with a low-pass filter (LPF) 40, the analog component is displayed directly on the meter, or an analog-to-digital (A / D) conversion with a sufficient number of bits to obtain the required resolution Is converted into a digital signal by a low-speed A / D converter 42 which is not so fast, for example, 16 bits, and digitally processed by a microprocessor 44 It was. The digital data output signal output from the microprocessor 44 is subjected to necessary processing by, for example, a parallel-serial converter, a shift register, a gate, a communication driver, and the like.

JP 2002-340505 A

  However, since an electric micrometer is composed of a differential transformer (inductor), it is impossible to balance the inductance and capacitance even if the balance is adjusted by a resistor. Cannot be set to zero. Further, since the excitation frequency cannot be increased due to the characteristics of the head 20 and is as low as 5 kHz, for example, the residual ripple component (5 kHz component) in the synchronous detector 38 in the subsequent stage of the circuit is large. Therefore, in order to remove the 5 kHz component, it is necessary to provide the LPF 40 having a low cut-off frequency in the subsequent stage of the synchronous detector 38, resulting in a decrease in response speed. For example, with a 0.1 μm resolution of a popular product, the frequency is about 20 Hz (−3 dB). However, in a high-precision electric micrometer that requires a resolution of about 1 nm, the cut-off frequency of the LPF 40 has to be further lowered in order to reduce the residual ripple component, resulting in a slower response speed and several hundreds There was a problem of becoming milliseconds (several Hz).

  On the other hand, it is conceivable to increase the excitation frequency of the head itself. However, in order to change something in the head, it is necessary to newly develop the head.

  The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to obtain a measurement signal having a high response speed from a differential transformer.

  The present invention is a signal processing apparatus of a differential transformer for obtaining a measurement signal having a high response speed from a differential transformer, and a first high-speed analog-to-digital converter that digitizes an output signal of the differential transformer; A second high-speed analog-to-digital converter that digitizes the drive signal of the differential transformer, and digital signal processing means that synchronously detects the differential transformer output signal by the drive signal, thereby solving the above-mentioned problem It is.

  Further, a phase adjuster for adjusting the phase difference between the drive signal and the output signal of the differential transformer is further provided.

  The digital signal processing means offsets the output signal to adjust the zero point.

  According to the present invention, a measurement signal having a high response speed can be obtained from a differential transformer. Therefore, the response speed can be increased from 10 times to 100 times by the circuit unit using the current head as it is.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 4, the present embodiment is an electric micrometer provided with a cartridge head or a lever head (simply referred to as a head) 20 having a 5 kHz specification as in the prior art, an oscillator 32, a drive amplifier 34, and a preamplifier 36. The output signal of the differential transformer via the preamplifier 36 is digitized at high speed, for example, a first high-speed A / D converter 60 of about 24 bits of flash type or ultra-high speed conversion type, and output from the oscillator 32. A phase adjuster 62 for adjusting the phase of the drive signal, and a second high-speed A / D conversion similar to the first high-speed A / D converter 60 that digitizes the output of the phase adjuster 62 at high speed And the digital output of the signal output from the first high-speed A / D converter 60 and the second high-speed A / D converter 64. It is obtained by a high-speed digital signal processor (DSP) 66 for synchronous detection by a driving signal.

  By using the high-speed A / D converters 60 and 64 and the high-speed DSP 66 in this way, the processing speed can be increased and the delay of the operation due to the LPF can be prevented.

  In the present embodiment, since the phase adjuster 62 is provided, the phase can be reliably matched. Depending on the specification, it can be omitted.

  It is also possible to adjust the zero point by offsetting the output signal in the DSP 66. Originally, the zero point of the bridge circuit should be adjusted using a variable resistor, varicap, variable inductance, etc. In this way, the digital value can also be adjusted in the DSP 66 by post-processing. is there. Even in this method, the phase component can be corrected and zero-set by digital computation, so that there is no deterioration in accuracy, and since it is a DSP, there is an advantage that a zero point can be automatically adjusted to a mechanical zero point by a program. Moreover, the zero point can be offset and set at a position desired by the operator through the DSP. Furthermore, the gain can also be set by the DSP.

  In the embodiment, the high-speed DSP 66 is used. However, a high-speed microprocessor can be used instead.

  In the above embodiment, the present invention is used in an electric micrometer. However, the scope of application of the present invention is not limited to this, and other electric micro products and general measuring instruments using a differential transformer are also used. Obviously, the same applies.

Configuration diagram showing the principle of differential transformer used in electric micrometer Similarly, a diagram showing an example of sensor coil output The block diagram which shows the structural example of the signal processing apparatus of the conventional electric micrometer The block diagram which shows the structure of embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Head 34 ... Drive amplifier 32 ... Oscillator 36 ... Preamplifier 60, 64 ... High-speed A / D converter 62 ... Phase adjuster 66 ... High-speed digital signal processor (DSP)

Claims (3)

A differential transformer signal processing apparatus for obtaining a measurement signal having a high response speed from a differential transformer,
A first high-speed analog-to-digital converter that digitizes the output signal of the differential transformer;
A second high-speed analog-to-digital converter that digitizes the drive signal of the differential transformer;
Digital signal processing means for synchronously detecting a differential transformer output signal by the drive signal;
A signal processing apparatus for a differential transformer, comprising:   2. The signal processing apparatus for a differential transformer according to claim 1, further comprising a phase adjuster for adjusting a phase difference between a drive signal and an output signal of the differential transformer.   3. The signal processing apparatus for a differential transformer according to claim 1, wherein the digital signal processing means performs offset adjustment of the output signal to adjust the zero point.

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