JPS62177406A - Displacement measuring instrument - Google Patents

Abstract

PURPOSE:To improve measurement accuracy without decreasing measurement efficiency by adding a bias voltage to the input signal of a signal amplifier so that the input signal of an A/D converter has an optimum input signal level and measuring the earth potential periodically. CONSTITUTION:A signal switching circuit 4 inputs respective detection signals 51-5n outputted by displacement detectors 11-1n which convert the displacement of each body to be measured into an electrical signal and an earth signal 50 and outputs them as a signal 6 selectively. Its output signal 6 is amplified 7 and digitized by an A/D converter 12. The signal level of the input signal to the converter 12 is put within an optimum input signal level range with a bias signal applied from a bias voltage generating circuit 8 to the input terminal of the amplifier 7, so the converter 12 is operated on the best condition. Further, a data arithmetic part A subtracts earth data corresponding to the earth signal 50 from respective detection data corresponding to the detection signals 51-5n outputted by the converter 12, thereby computing displacement data on each body to be measured. Therefore, measurement errors due to the zero point conversion of the amplifier 7 and converter 12 following the circuit 4 are removed from the data.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a displacement measuring device capable of simultaneously detecting the displacement of multiple objects to be measured, and particularly relates to a displacement measuring device that can simultaneously detect the displacement of multiple objects to be measured, and particularly to a displacement measuring device that can detect displacements of multiple objects to be measured. The present invention relates to a displacement measuring device that improves accuracy deterioration due to zero point fluctuations and input signal level fluctuations of an A/D converter.

[Prior Art] For example, the displacement of an object is quantitatively measured, and the obtained displacement data is arithmetic-processed by a processing device.
In a control system that feeds back the operational position of the object to a control system, a displacement detector incorporating a differential transformer or the like converts the displacement of the object to be measured into an electrical signal. Then, the detection signal output from the displacement detector is amplified by a signal amplifier, and then converted into digital displacement data by an A/D converter. The processing device executes various arithmetic operations using this digitally converted displacement data.

In addition, when measuring the displacement of multiple objects to be measured simultaneously, a dedicated displacement detector is installed for each object to be measured, and the detection signals output from each displacement detector are time-divided by a signal switching circuit. The signal is taken out and input to an A/D converter via a signal amplifier. Therefore, each piece of displacement data is sequentially input to the processing device at regular intervals.

In a displacement detector used in such a displacement measuring device, a voltage proportional to the amount of movement of a movable rod constituting the displacement detector from a reference position of a main body of the displacement detector is output as a detection signal. Therefore, if the position of the movable rod that moves in conjunction with the n1 constant object is aligned with the reference position before starting measurement, the detection signal will be an absolute value including + and - (0±A
) is output as Furthermore, when the position of the movable rod is adjusted to a position moved from the reference position by a predetermined amount in the child direction, the detection signal is the deviation value (Ao
±A). And the voltage value (0±A) output from each displacement detector.

The detection signal of (Ao+A) is α
The signal is amplified twice and input to the A/D converter.

Then, this A/D converter converts it into digital displacement data.

[Problems to be Solved by the Invention] However, the above-described displacement measuring device has the following problems. That is, there is generally an optimum human signal level range for the human signal level of the A/D converter. Therefore, the signal level of the detection signal output from the signal amplifier needs to fall within the optimum signal level range.

However, as mentioned above, the signal level of the detection signal output from the signal amplifier has two types of signal levels α(θ±A) and a(AOf
:A), it is difficult to always maintain the input signal level of the A/D converter at an optimum value only by adjusting the amplification degree of the signal amplifier. Therefore, the function of the A/D converter cannot be used effectively, resulting in the problem that the number of effective digits of the obtained displacement data is insufficient or the data is saturated. In particular, if the detection signal at the signal input terminal of the signal amplifier has a zero point fluctuation of, for example, +X (or -y), the signal level of the detection signal input to the A/D converter will be
α(O±Ax, -y), a (Ao±Ax, -
y), and there is a high probability that the signal level will deviate significantly from the optimum human power signal level range. Also, if the same +X (or -y) zero point fluctuation occurs at the signal output end of the signal amplifier,
The signal level of the detection signal input to the /D converter is [α
(0±A) +X, -yl r[α(AD +A) 10X
, -y, and there is still a high probability that the input signal level will deviate from the optimum input signal level range.

Furthermore, electronic equipment that handles DC signals, such as signal amplifiers and A/D converters, is prone to zero point fluctuations as described above.
Before starting mj determination, it is necessary to perform zero point adjustment to adjust the input and output signals of the signal amplifier to zero volts while the movable rod of each displacement detector is mechanically aligned with the reference position of the displacement detector body. .

However, when it is necessary to continuously measure the displacement of a large number of objects to be measured, it is difficult to perform the above-mentioned zero point adjustment in a short period.

There is also the problem that if an electronic device with less zero point fluctuation is used, the entire device will be expensive.

The present invention has been made based on these circumstances, and its purpose is to apply a bias voltage to the input signal of the signal amplifier so that the input signal of the A/D converter reaches the optimum input signal level. By periodically measuring the ground potential at the same time, it is possible to operate the A/D converter under optimal conditions, minimize errors caused by zero point fluctuations, and improve measurement accuracy without reducing measurement efficiency. The purpose of this invention is to provide a measuring device.

[Means for solving the problem] In the displacement AI determination device of the present invention, each detection signal and ground signal output from each displacement detector that converts the displacement of each measured object into an electric signal is input. At the same time, a signal switching circuit is provided to selectively output each of these input signals.
The signal output from this signal selection circuit is amplified by a signal amplifier, the amplified signal is converted to A/D by an A/D converter, and the signal input to this A/D converter is converted into an A/D converter. A predetermined bias voltage is applied to the input terminal of the signal amplifier by the bias voltage generation circuit so that the input signal level falls within the optimum input signal level range of the converter, and the data calculation section calculates the value of each displacement detector output from the A/D converter. The displacement data of each object to be measured is calculated by subtracting the ground data corresponding to the ground signal from each detection data corresponding to the detection signal.

[Operation] With the displacement measuring device configured in this way, the signal level of the signal input to the A/D converter after being amplified by the signal amplifier is determined by the bias signal applied to the input terminal of the signal amplifier. Therefore, the A/D converter is used under optimum conditions because the input signal level is within the optimum input signal level range of the A/D converter. Also,
Since the value obtained by subtracting the ground data corresponding to the ground signal, which is the reference potential of the ground potential, from each detection data obtained from the A/D converter in the data calculation section is used as the displacement data of the measured object, this displacement data In this method, measurement errors caused by zero point fluctuations of the signal amplifier and A/D converter after the signal switching circuit are eliminated.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of the displacement 14111 fixing device u of the embodiment. In the figure, 1 to 1rL are n displacement detectors each measuring the displacement of n objects to be measured (not shown), and each displacement detector 1 is equipped with a differential transformer, etc. It consists of a main body 1a and a movable rod 1b that moves in conjunction with the displacement of the object to be measured. When the movable rod 1b moves from the reference position of the displacement detector main body, a detection signal proportional to the amount of movement is output. The detection signals output from the displacement detectors 11 to 1rL are amplified by amplifiers 21 to 2π, respectively, and then noise components are removed by low-pass filters 3□ to 3rL to convert them into DC detection signals, which are used by the signal switching circuit 4. It is input to each input terminal 51 to 5rL.

The 0th input terminal 5° of this signal switching circuit 4 is grounded. Therefore, a ground signal whose potential is at the ground level (0 potential) is input to the 0th input terminal 5°. Each input terminal 50 to 5rL is a contact SO=S
It is connected to the common output terminal 6 via n. Each of the contacts S o and -S n is composed of an analog switch, and is controlled on/off by a control signal input from the outside. Note that two or more contacts S are never closed at the same time. Therefore, this signal switching circuit 4 has input terminals 5° to 5rL from Oth to nth.
The input signal is selectively taken out from the output terminal 6.

The output signal output from the output terminal 6 of the signal switching circuit 4 is input to the signal input terminal of the signal amplifier 7. A predetermined bias voltage output from a bias voltage generation circuit 8 is applied to a bias input terminal of the signal amplifier 7. In this bias voltage generation circuit 8, variable resistors 9a and 9b having different resistance values are interposed between a power supply terminal for a DC reference voltage vR outputted from a power supply circuit (not shown) and the ground. The variable terminals of each variable resistor 9a, 9b are connected to the selection terminals a, b of the changeover switch 10, and the changeover switch 1
The common terminal C of 0 is connected to the bias input terminal of the signal amplifier 7. The changeover switch 10 changes the bias voltage applied to the signal amplifier 7 to each of the displacement detectors 11 to 1r.
Is the signal level of the L detection signal the absolute value (0±A) level including + and - mentioned above, or is the deviation value only on the + side (
AO+A) level is selected and set in advance before starting measurement.

The signal amplified by the signal amplifier 7 is sampled and held (
S/H) circuit 11 samples the signal. Analog data sampled by this sample φ hold circuit 11 is converted into digital value data by an A/D converter 12 at the next stage.

The data output from the A/D converter 12 is input to an I10 port 13 that constitutes a data calculation section.

As shown in the figure, this data calculation section incorporates a CPU (central processing unit) 14 that executes various calculation processes, and this CPU 14 calculates displacement data and controls switching of the signal switching circuit 4 via a pass line 15. ROM1B, I10 port 1, which stores control programs etc. for implementing
Controls the RAM 17 that temporarily stores variable data such as data input from the third or other sources. Also, the I10 port 13. to which the data is input. I10 port 18 that sends a switching signal to the signal switching circuit 4. I10 boat 20 sends print data to a printer 19 that prints out calculated displacement data
etc. are connected to the CPU 4 via the path line 15.

In such a configuration, when initially setting the movable rod 1b in each of the displacement detectors 11 to 1n to the reference position of the displacement detector main body 1a before starting measurement, the changeover switch 10 of the bias voltage generation circuit 8 is set to the selection terminal. When the movable rod 1b is moved a predetermined distance from the reference position, the selector switch 10 is set to the selection terminal side.

When a start signal supporting the start of measurement for each object to be measured is inputted from the outside, the CPU 14 of this data calculation section controls the signal switching circuit 4 via the I10 port 18, as shown in FIG. Send a signal and contact so
+ SL + S2 + ....

SrL is sequentially closed for a period To. Then, the ground signal and each detection signal are input to the signal input terminal of the signal amplifier 7 for each period To. Since the bias voltage selected and set by the changeover switch 10 is applied to the bias input terminal, the signal amplifier 7 amplifies the signal obtained by adding the bias voltage to the input signal by a factor of α, for example, and sends it to the sample-and-hold circuit 11. do. The sample and hold circuit 11 samples the input signal and sends it to the A/D converter 12. A/D converter 12 converts the input data into digital data. Therefore, the I10 port 13 receives ground data D for the ground signal as shown. , detection data DI + D2 + . . . for each detection signal
, Dn are input sequentially.

The CPU 14 subtracts the first input grounding data Do from each of the detection data D1 to Dn to obtain displacement data for each object to be measured (CD1Do).

Find (D2-D(1), -, (DrLDg),
It is printed out using the printer 19.

If the displacement measuring device is configured in this way, for example, A
The optimum input signal level of the /D converter 12 is (-B to 10B)
In this case, the bias voltage generation circuit 8 is adjusted so that each data value input to the A/D converter 12, that is, the signal level range input to the sample-and-hold circuit 11 falls within the above range (-B to 10B). It is possible to adjust the resistance value of each variable resistor 9a, 9b and the amplification factor α of the signal amplifier 7. This adjustment work only needs to be performed once before starting the '/IJI determination. Therefore, A/D conversion'
512 can be operated under optimal conditions at all times, measurement accuracy can be improved.

Furthermore, in the embodiment, two types of bias voltage values are set for each variable resistor 9 corresponding to the two types of initial setting methods of absolute value measurement and deviation value measurement described above for each displacement detector 11 to 1rL.
Since the settings are made in advance using the switches a and 9b, and the settings can be changed as needed using the changeover switch 10, the efficiency of measurement work can be improved.

Also, ground data D for a ground signal input to the input port 13. includes the bias voltage manually inputted from the bias voltage generation circuit 8, the zero point variation of the signal amplifier 7, the zero point variation of the sample/hold circuit 11, and the A/D converter 12.
This includes the zero point fluctuation of 2 minutes, etc. On the other hand, each detection data input to the input port 13 includes the detection signal output from each displacement detector 1, the zero point variation of the amplifier 2, the zero point variation of the low-pass filter 3, and the bias voltage.

Zero point fluctuation of signal amplifier 7, sample/hold circuit 1
1, the zero point fluctuation of the A/D converter 12, etc. are included. Therefore, each calculated displacement data (DI
Do), -, (Dn-Do) only include the detection signal of each detector 1, the zero point fluctuation of each amplifier 2, and the zero point fluctuation of the low-pass filter 3, and the Errors due to zero point fluctuations due to each component are eliminated. Therefore, the measurement accuracy of the entire displacement measuring device can be improved.

Furthermore, since the level measurement of the ground signal is automatically carried out every cycle of displacement measurement of each object to be measured, it is possible to improve all constant work efficiency without reducing measurement accuracy.

Furthermore, as mentioned above, since the zero point fluctuation is corrected by measuring the ground signal for each Alj constant,
Bias voltage generation circuit 8. Since the signal amplifier 7, the sample/hold circuit 11, and the A/D converter 12 do not need to be expensive electronic devices with little zero point fluctuation, the manufacturing cost of the entire displacement measuring device can be reduced.

[Effects of the Invention] As explained above, according to the present invention, a bias voltage is applied to the input signal of the signal amplifier and the ground potential is periodically applied so that the input signal of the A/D converter reaches the optimum input signal level. I try to measure it. Therefore, the A/D converter can be operated under optimal conditions, and errors caused by zero point fluctuations can be minimized, and measurement accuracy can be improved without reducing measurement efficiency.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration for determining displacement tlljll according to an embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation of the embodiment. 11-1rL...Displacement detector, 2,-2rL...Amplifier, 31-3L...Low-pass filter, 4...Signal switching circuit, 50-5rL...Input terminal, 6... Output terminal, 7... Signal amplifier, 8... Bias voltage generation circuit, 9a.

Claims (1)

[Claims] A plurality of displacement detectors that detect the displacement of the object to be measured and convert it into electrical signals, a ground signal, and each detection signal output from each of the displacement detectors are input, and each of these input signals is selected. A signal switching circuit that uniformly outputs a signal, a signal amplifier that amplifies the signal output from the signal selection circuit, and an A/D converter that A/D converts the signal amplified by the signal amplifier.
a converter, and the signal input to the A/D converter is connected to the A/D converter.
a bias voltage generation circuit that applies a predetermined bias voltage to the input terminal of the signal amplifier so as to fall within the optimum input signal level range of the A/D converter; A displacement measuring device comprising: a data calculation unit that calculates displacement data of each of the objects to be measured by subtracting ground data corresponding to the ground signal from each detection data corresponding to the detection signal.