JPS58137709A - Reading method of scale - Google Patents

Abstract

PURPOSE:To increase reading speed while improving accuracy with respect to a high speed reading method of digital scales by dividing pitch to multiple parts. CONSTITUTION:Even if the same scale signal is used, the pulse signal outputted from a zero cross detection circuit and the timing when the output of the pulse signal of a phase modulating 100-division circuit changes over from 9.9mum to 0.0mum do not always coincide. Therefore, if the signals of said two systems are added, a large error is produced. In order to prevent such error, the latch output of the 2nd counter is conducted to a carry-up/carry-down pulse generating circuit, and when 9.9 changes to 0.0 in the case of an UP direction, a carry-up signal is generated and when 0.0 changes to 9.9 in the case of a DOWN direction, a carry-down signal is generated. Such carry-up and carry-down signals are fed to the 1st counter and are used as the digit signals of 10mum at the low speed when the phase modulating 100-division circuit is in normal operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that electrically divides the graduations of a digital scale into multiple parts, reads them at high speed, and displays them digitally.

In known methods for reading digital scales, the number of divisions of one pitch (CP) and the reading speed are in a contradictory relationship, and when the number of divisions is increased, the reading speed is inevitably limited. The present invention provides a scale reading method that does not cause reading errors even when the scale is divided into multiple parts and the moving speed is high.

There are several well-known dividing methods5.

First, the zero-cross method (wave number measurement division method), which is one of the division methods, will be explained with reference to Fig. 11s1. The waveforms shown in (A) and (R) in the figure have mutual phases of P/4.
By generating a pulse signal at the zero-crossing point of the shifted scale signal, a signal (c) obtained by dividing the 1P interval into four is obtained. Although this method is extremely effective for high-speed reading K, it is usually impossible to divide into four or more.

Another conventional division method is a method using resistance division.

This creates electrically out-of-phase signals through resistors,
This method divides the data at the zero-crossing point, and can handle relatively fast reading, but in practice, the maximum division rate is 20 minutes.

As a multi-division method of 20 or more divisions, a phase modulation division method is usually used. In this method, the read signal is obtained as follows.

The two signal waves obtained from the scale are converted to 2π by 1-A1・s in p' e Hz -A:
z・aos! t (where t is the displacement amount and P is the scale pitch), and this is the carrier signal e1meo-o
When modulated and added by os aJt s@12-eo-sin atK, E -IC, * +E -0-A-BiH(@t+
01122 P phase modulation signal. This makes the displacement signal a function of time, and the displacement can be determined by detecting the phase difference.

In Figure 3, which shows these relationships, the waveform E shown in (d) is the phase modulated signal wave obtained by the above formula (
E shown in e) is a square wave of E, and is the waveform when the displacement f wm Q is 80. (f) indicates a clock pulse signal (CK). Here, when X displaces Δ, the waveform (e) becomes a wave 1g shown by ())ic, and a phase difference of Δ♂ is generated between E and E.

Interpolating CK during this period, reading P/N units from K (
A signal is obtained. This 6g appears every period of sin ω7, and as it is, the interpolated pulse of Δ5 is counted repeatedly, so in a counter using the normal phase modulation division method, it is necessary to devise a way to adjust the phase difference every period of gin aJt. is being done.

According to this method, multiple divisions are possible, but as mentioned above, the reading speed is limited as the number of divisions increases, making high-speed reading impossible.

The present invention solves these problems and provides a scale reading method that allows multi-division and high-speed reading.

The present invention will be described in detail below assuming that the number of divisions between the scale pitches is 1'-10 μm x 1 pitch, N-100, and the minimum reading value P/N-α1 μm, but the method of the present invention is not determined by these.

FIG. 3 shows the basic concept of the present invention.

When measuring the length X, the measurement starting point P1 is at an arbitrary position on the scale.
The value of can be read using the phase modulation division method described above. At the start of measurement, this M is read and memorized.Then, by displacing along the scale, a sin waveform school signal is detected, and a pulse is generated every time a zero crossing point is passed depending on the pitch of the scale. This pulse II (S) is counted and stored. End point of measurement (Pa)
Then, as at the starting point, the value M2 from the last 13 zero points passed through is read using the phase modulation division method and the measurement is completed. Two memorized values CM1. n
) and the last measured value M2, then X-n P + M
2 M 1 can be calculated to know the amount of displacement X.

However, if the operating speed of the phase modulation dividing circuit and the above calculation processing speed are low enough to respond, the above calculation is not performed only at the end of the measurement.
It is also possible to calculate and display using the count value and M2 that follow the momentary displacement.

A circuit for realizing this method is shown in FIG.

27r 27r Two scale signals B 1np t e OO11p
' is applied to the phase modulation 100 division circuit.Here, by the phase modulation division method described above, a pulse signal proportional to the amount of displacement within one pitch of the scale signal is outputted every period of sin t. This pulse signal is refreshed and counted every sin alt period by the next second counter, and in this embodiment becomes a display signal of 1 μm and 01 μm digits. At the start of measurement, a measurement starting point setting signal is applied externally, and the contents of this second counter are stored in the M1 memory circuit ◎In addition, a scale signal 81n2f
f is also applied to the zero loss detection circuit, and is applied to the scale signal voltage by 1 every pitch (10 μm in this example):
A pulse signal of I is generated. When the displacement speed is faster than the predetermined limit, the AB signal switching circuit is set to pass the B signal, that is, the pulse signal every 10 μm from the zero cross detection circuit, and the pulse signal every 10 μ- is sent to the next first counter.・The M stored at the start of measurement, the contents of the memory circuit, and the contents of the first and second counters at the present time are led to the calculation section, simple addition and subtraction calculations are performed, and the results are displayed on the display section. By doing so, you can know the current amount of displacement @ However, as mentioned above, when moving at high speed, the phase chamber 1□1 key division system does not indicate the correct value, so the contents of the second counter are unreliable, and as a result, when moving at high speed, The reading accuracy in this example is only 10 μm, but during high-speed movement, the 1 μm and 01 μm display constantly fluctuates, making it impossible to read visually, so this poses no problem in practice.

When measurement with an accuracy of 0.1 μm is required, the measuring device is usually at a standstill or in a slow state at the starting and ending points of the measurement. The advantage of the present invention is that even if the speed increases during intermediate movement and an error occurs in the contents of the second counter, the second counter is a refresh counter, so it can show the correct value again when the speed becomes low at the end point. This is a major feature.

Therefore, the method of high/low speed switching, which plays an important role in this system, will be described next.

Even if the same scale signal is used, the timing at which the pulse signal every 10 μm output from the zero cross detection circuit and the pulse signal output from the phase modulation 100 division circuit changes from 99 μm to 0.0 μm does not always coincide. Therefore, if the two series of signals are simply added together, a large error will occur. For example, if the pulse from the zero cross detection circuit is output 0.1 μm earlier, the display will be 0.0, 0.1, 0.2 - - -
- - 9.8, 19.9, 10.0, 10.1 -
..., and conversely, if the output is delayed by 11 μm, the display will be α0.0.1. α2...9.8.9.9,0
．． 0.

10.1, resulting in a very large error.

To prevent this, the latch output of the second counter is sent to the carry/carry down pulse generation circuit, and when 99 changes to 0.0 in the UP direction, a sail up signal is generated, and in the DOWN direction, a 0.0 signal is generated.
When the phase modulation circuit changes to 9.9, a digit signal is generated, and at low speeds when the phase modulation 100 division circuit is operating normally, this carry/carry/decrease signal is sent to the first counter and used as a 10 μm digit signal.

In addition, at high speeds, the signal of the phase modulation 100 division circuit does not show the correct value, so the signal of 10 μm from the zero cross detection circuit
Each signal is used. The circuit for this purpose is an AB signal switching circuit. This will prevent large errors as shown in the example (0, 0, Q, 1.α2...9.8.9.
9. A correct display can be obtained such as I Q,, 0.1α1... The next problem is the timing of this switching. In the case of switching to a down signal, the zero cross detection signal is output slightly earlier and the first counter is counted, and then the switch is made, and if the carry signal is output later, the same scale point will be counted twice.

FIG. 5 shows this relationship. In the figure, (phosphorus is a scale signal, (nu) is a zero cross detection signal, (ru) is a clock pulse signal, and (o) is a carry carry down signal. This zero cross detection signal (nu) and carry carry down signal ( (e) is not necessarily the same.Therefore, these two
If switching is performed between two pulse signals by the switching signal shown in (wa), both pulses will be counted as shown in (force), resulting in a miscount. Therefore, the period between the rising edge of the first pulse of the (force) signal and the falling edge of the subsequent pulse is set as an area (y) where switching is prohibited, and the pulse that was conventionally counted (for example, in the case of a switching signal from high speed to low speed) counts the zero-crossing detection signal (nu)), and the actual switching is performed at the position indicated by the signal (ri) after the end of the switching prohibition period, so the pulse (o) is not counted.

By providing the switching prohibited section in this manner, switching between high speed and low speed can be performed without miscounting.

As described in detail above, the present invention has achieved the result of being able to perform multi-division and high-speed reading, which was considered impossible in the past, and is capable of practical digital measurement with high speed and high precision.
') It became possible to donate.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the conventional zero-cross division method, FIG. 2 is an explanatory diagram of the conventional phase modulation division method, 3rd WJ is a detailed explanatory diagram of the present invention, FIG. 4 is a block diagram of the present invention, and 5th
The figure is an explanatory diagram of a switching prohibited section. Tokusaku Applicant Co., Ltd. Tokyo Precision Procedure Amendment (Method) 2 Method of reading the name scale of the invention 3, 1 Relationship with the case of the person making the correction Patent Applicant Address 4, 9-7-1, Shitatsujaku, Mitaka City, Tokyo; 4
Date of official order: May 25, 1982 (Shipping date: 5, application subject to amendment and specification 6: Contents of amendment)

Claims (1)

[Claims] (1) In a method for reading a digital scale that outputs a periodic signal in response to displacement, a periodic pitch C of the scale is provided.
It has a first counter that counts the value (M, ) is stored, and the displacement amount X-5P+M2 is calculated from the count value (ru) of the first counter obtained by the displacement and the value CM2) shown on the second counter at the end point.
A high-speed, multi-division scale reading method that calculates and displays M. 7T: A scale reading method in which the I-pulse is used as the counting signal of the first counter, and the zero-crossing point of the scale pitch is used as the counting signal at high speed. (8) Claims 1 and 2. In the description, scale signals sin t, oo@-2X-t(
z is the amount of displacement) and the reference waveform 8111ωt to create a moving waveform 5 inches (a + t + "τ The refresh count is performed by the second refresh counter to a count value of 1 pitch or less, and switching is performed according to the classification of high speed and low speed. A scale reading method in which the count value is the count value, and at low speed, the carry-down signal by the opuff p-pulse of the second kakunta is used as the count value of @1 carant. In,
A scale reading method that switches the input signal between high and low speeds and sets the area between the zero cross signal and the carry/carry/down pulse as the switching stop area.