JPS58108405A - Air micrometer having corrector - Google Patents

Abstract

PURPOSE:To automatically correct errors due to zero-shift temperature characteristics, by shutting off the pressure supply air to present a state of differential pressure 0, detecting and storing the output voltage value, and subtracting the value from the output voltage value in the measurement carried out later. CONSTITUTION:When a solenoid valve 16 is closed, both pressures inside differential pressure chambers 1, 2 become equal to the atmospheric pressure. In other words, the differential pressure chambers 1, 2 have a pressure difference DELTAp=0 therebetween, and the output voltage Vout of a differential pressure converter 13 at this time is b'. A controller 18 receives and stores the value of b'. The solenoid valve 16 is opened, and the positive and negative signs are inverted to calculate -b', which is applied to an adder 17 through a feedback line 21. The adder 17 adds -b' to the value of the output signal from the differential pressure converter 13 and delivers the result as a corrected output voltage. Since -b' is added to the output voltage characteristic curve 15 after change, the curve 15 downwardly moves parallelly by the dimension of b'.

Description

[Detailed Description of the Invention] The present invention relates to an air micrometer, and in particular,
Figure 1 relates to an air micrometer equipped with an electrical detection display means and configured to automatically correct errors caused by drift due to changes in external conditions. FIG. 2 is a cross-sectional view for explaining the working principle of a conventional air micrometer equipped with an electric detection means.

The air micrometer is provided with a reference differential pressure chamber l and a measurement differential pressure chamber 2, and the reference differential pressure chamber l faces a fixed gap forming device 4 via a nozzle 3, and the gap between them is is fixed at a predetermined fixed gap xO. The differential pressure chamber 2 for measurement is opposed to the object to be measured 6 via the nozzle 5, and the distance X is the gap to be measured.

The two nozzles 3 and 5 mentioned above are formed to have the same shape and size.

-B The two differential pressure chambers 1.2 are each communicated with a supply chamber 9 via a nozzle 7.8, and this supply chamber is supplied with pressurized air via an air line 11 from a pressure air source 10. sent.

Depending on the usage conditions of the air e-micrometer, a gas such as nitrogen may be used instead of the above air. In the present invention, air means a gas used in an air micrometer.

Reference numeral 12 denotes a pressure regulating valve for keeping the air pressure fed into the supply chamber 9 constant.

The nozzles 7 and 8 are formed to have the same shape and size.

The atmospheric pressure in the reference differential pressure chamber 1 and the atmospheric pressure in the measurement differential pressure chamber 2 are connected to and communicated with the differential pressure converter 13, respectively. The difference is detected and a voltage proportional to the pressure difference is generated, and the above voltage is amplified at a rate of one foot to produce an output voltage V. Output ut. Recently, semiconductor pressure-sensitive elements are often used for differential pressure detection, and semiconductor amplifier circuits are often used for output voltage amplification.

11Sho 5s-tos4os (2) Conventional air micrometer as above (Fig. 1)
A method of measuring the measurement gap X using the following will be described below.

Air at a constant pressure is supplied to the supply chamber 9 via a pressure regulating valve 12 (7), and this pressure air is supplied to a reference differential pressure chamber l and a measurement differential pressure chamber via nozzles 7 and 8, respectively. It flows into the pressure chamber 2, flows through the nozzles 3.5, and is discharged into the atmosphere.

As described above, nozzles 7 and 8 and nozzles 3 and 4 are formed to have the same shape and size, so the measurement gap X is the fixed gap X. , the atmospheric pressure in the measurement differential pressure chamber 2 becomes equal to the atmospheric pressure in the reference differential pressure chamber l. Therefore, the output voltage V of the differential pressure converter 13. ut becomes zero.

Furthermore, when the measurement gap X is different from the fixed gap XI), a difference occurs between the air flow rate flowing out from the nozzle 3 and the air flow rate flowing out from the nozzle 5, and accordingly, the atmospheric pressure in the differential pressure chamber 2 for measurement A pressure difference occurs between the atmospheric pressure in the reference differential pressure chamber l. Therefore, the differential pressure converter 13 outputs an output voltage v, ut corresponding to the above pressure difference, so that the output voltage V corresponds to a change in the difference between the measurement gap X and the fixed gear tooth XO. By checking the state of change of ut in advance and comparing it with this, the value of the measuring force X can be calculated.

The conventional air micrometer is 1μ as described above.
Although it is possible to measure extremely small dimensions on the order of m, there are technical problems such as missing parts when attempting to measure extremely small dimensions on the order of 0.1 #m.

(a) Even if the temperature and humidity of the supplied air change slightly, the 0.
Measured values change to an extent that cannot be ignored for measurements on the order of 1 μm.

(b) Due to the temperature characteristics of the differential pressure detection section and signal amplification section of the differential pressure converter 13, even normal changes in room temperature
．． For measurements on the order of 14 m, the measured value changes to an extent that cannot be ignored.

The above changes are shown in FIG. The horizontal axis shows the reference differential pressure chamber l.
The pressure difference ΔP between the atmospheric pressure inside the chamber and the atmospheric pressure inside the differential pressure chamber 2 for measurement is expressed as the vertical axis, and the output voltage V of the differential pressure converter 13 is plotted on the vertical axis. I took ut.

A curve 14 shows the initial characteristic of ΔP-vout at the time when the inspection and adjustment of the air micrometer is completed, and the initial characteristic line of the curve is sufficiently approximated by the following linear equation (tl).

vout ” '・Δp+b 廂・・・・・・・・・
...Group...Old...Group-fl) The initial characteristic M14 illustrated in Fig. 2 has been adjusted to b-o and is in good condition, so in this case, vout ''・Δ
P・・・・・・・・・・・・Opening・・・・・・・
・・・Ujouyo・(Represented by ke.

When the atmospheric temperature, humidity, etc. change over the period of immersion after completing the adjustment as described above, the above-mentioned ΔP-vout characteristic line changes as shown by curve 15, and is approximated by the following equation.

vout ” a'・Δp+b' ・Old...Egg weight...River...River...Old...+21 In the above formula, a and 'a' are pressure car voltage' gain coefficients. , b, b′
is the offset voltage.

For example, when a semiconductor pressure-sensitive element is used, bl (offset voltage) of equation (2) occurs due to the zero-point shift temperature characteristics of this element, which becomes an error factor. The above zero point shift temperature characteristic is, for example, on the order of 1.2 x 10' Kf/m2/C.

In addition, the amplifier that amplifies the output voltage of the pressure-sensitive element has drift, and due to gain stability error, the pressure-voltage gain coefficient a in the initial state changes to a', causing an error. The above drift is, for example, 0.5 x 10-
2mV (input conversion value), gain stability is, for example, 0. O1
%/°C and is on the order of nine times.

Due to the error factors mentioned above), the differential pressure -P in Figure 2
When the value of is Δp2, according to the initial output voltage characteristic line 14, the output v, ut should be ma2, but according to the changed output voltage characteristic lll115, it becomes ma2'. arise.

In order to reduce the above error, it is effective to reduce the differential pressure ΔP. To put this differently, the measurement gap X in FIG. 1 should be fixed as much as possible. Errors can be reduced by performing measurement in a state where the pressure in the differential pressure chamber 2 for measurement is not significantly different from the pressure in the differential pressure chamber 1 for reference.

In the second factor, when the differential pressure ΔP is about jpl, the output is V according to the initial output voltage characteristic @14. According to the output voltage characteristic a15 after the change, where ut should be 1, it becomes 1', which results in an error of σ1, but in this case, the error σ
1 is significantly reduced compared to the error σ2 in the above case.

However, even if the differential pressure ΔP is minimized to a state of Δpo-o, an error corresponding to the ordinate value b' of the intersection of the output voltage characteristic 1I115 after the change and the vertical axis remains.

The present invention has been made in view of the above-mentioned circumstances, and provides an air micrometer equipped with a correction device that automatically corrects the error b' caused by the above-mentioned zero point movement temperature characteristic and enables highly accurate measurement. The purpose is to

To achieve the above object, the present invention creates a state of ΔP-0 by cutting off the pressure supply air supplied to the air micrometer, and the output voltage V in this state. Output voltage V that detects the value of ut (b/ in FIG. 2) and stores it for subsequent measurements. ut
`` ``By subtracting b', which was stored as described above, from Δp+b', the output voltage is vout.
”・The invention was completed as a result of research on a configuration that can correct for ΔP, and the invention on page 9 of this book involves intervening and connecting a solenoid valve to cut off the supply air in the air pipe line. , an adder for subtracting the error (b' in Figure 2) is connected to the output circuit of the differential pressure converter, and a controller is provided separately from the above, and the output voltage is stored in this controller. A calculation function to invert the sign of the stored value, a function to give the inverted stored value to the adder, and a function to open and close the solenoid valve. The present invention is characterized in that it is configured such that zero point movement caused by temperature characteristics of the differential pressure converter can be automatically corrected.

Next, one embodiment of the present invention will be described with reference to FIG. Components with the same drawing reference numbers as in Figure 1 are shown in Figure 1 (
Since the components are the same as those in the conventional device, their explanation will be omitted.

A solenoid valve 16 is interposed and connected to the air pipe line 11.

An adder 17 is connected to the output circuit of the differential pressure converter 13.

A controller 18 is provided separately from the above. This controller is configured to have the following functions: (1) Output voltage V. Function to receive and store the value of ut via the signal line 19.

(1) During the period when the above output voltage value is received, the solenoid valve 16 is operated to close via the control line.
l) An arithmetic function that inverts the sign of the output voltages vc and ut received via the signal line 19.

4V) The above calculation result is fed back to the feedback line 21.
to the adder 17 via the adder 17, and causes the adder 17 to add the above calculation result to the output voltage of the differential pressure converter 13. The present invention is configured as described above, so this can be used. This allows for automatic corrections to be made, such as when there is a shortage.

A program is installed in the controller 18 in advance, and after the initial inspection and adjustment are completed, the controller 18 is programmed at regular intervals.
Alternatively, the following correction operation is performed every time a certain number of measurement operations are performed.

a), BON) (1-The solenoid valve 16 is closed when the adder 17 is not commanded to perform addition from the controller 18.

As is clear from the configuration shown in FIG.
When the differential pressure chambers 1.2 are closed, the pressure inside both differential pressure chambers 1.2 becomes equal to atmospheric pressure. Looking at this in Figure 2, there are two differential pressure chambers 1
．． A state is reached where the pressure difference between the two is ΔP-0. Therefore, the output voltage V of the differential pressure converter 13 at this time. ut becomes b'. b) 8th controller) The o-ra 18 receives and stores the value of b' mentioned above.

C), the solenoid valve 16 is opened.

d) Calculate -b' by inverting the sign of the stored value b'.

e) This -b' is applied to the adder 17 via the feedback line 21. Adder 17 adds -b' to the output signal value of differential pressure converter 13 and outputs this as a corrected output voltage.

As a result of the above-described operation, the output voltage characteristic line 1 after a period of time when the initial output voltage characteristic line 14 described for the second factor is formed.
5, the output voltage characteristic 1 after this change
Since -b' is added to II15, it is translated downward by the dimension b', resulting in the correction characteristic 1l122 shown by the tentative attack line.

The above correction characteristics, I! 22 passes through the coordinate origin and intersects with the initial output voltage characteristic 11114 at the coordinate origin.

As described above, due to the action of the device of the present invention, the output voltage characteristic @15 that has changed over time is corrected as shown in the correction characteristic line ρ, so that when the differential pressure ΔP is Δp2, the above correction characteristic line n Then, as the output voltage v, ut, ma2'' is obtained.And when the differential pressure ΔP is pl, the output voltage V.u
In this way, according to the present invention, the error due to zero point movement caused by the temperature characteristics of the differential pressure converter (bl shown in Fig. 2) is automatically corrected. The measurement accuracy is significantly improved.As is clear from the characteristic diagram shown in Fig. 2, according to the complementary characteristic line ρ when the present invention is used continuously, the error is reduced as the measurement is performed with ΔP as small as possible. Therefore, it is desirable to perform measurements with the measurement gap X explained with reference to FIG. 1 close to the fixed gap X. In other words, when X'-v
! ; 0, the error caused by the temperature characteristics of the differential pressure converter (3) can be ignored.

The fourth figure is a chart showing the change in offset voltage over time in the conventional device using a curve, and the change over time in the offset voltage in the above embodiment using a curve. ± change
As a result, the measurement accuracy of the air micrometer can be improved from the conventional ±0.5 μm to ±0.1 μm.

As explained above, the present invention connects a solenoid valve in an air pipe line, connects an adder in an output circuit of a differential pressure converter, and provides a controller separately from the above. A function to store the output voltage in the lever controller, a calculation function to reverse the sign of the stored value, a function to give the reversed stored value to the adder, and a function to open and close the solenoid valve. By configuring the differential pressure converter to have , it is possible to automatically correct the zero point movement caused by the temperature characteristics of the differential pressure converter and perform highly accurate measurement.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventionally commonly used air micrometer, Fig. 2 is a chart showing the output voltage characteristics of a differential pressure converter, and Fig. 3 is a diagram of a micrometer equipped with a correction device according to the present invention. FIG. 4, which shows one embodiment and corresponds to the factor 11k in the conventional device, is a chart showing the change in offset voltage over time for the above embodiment and the conventional device. l...Differential pressure chamber for reference, 2...Differential pressure chamber for measurement, 3
゜5.7.8... Nozzle, 4... Fixed gap forming device, 6... Measured object, 9... Supply chamber, 11... Air pipe line, 12... Pressure adjustment valve , 13... Differential pressure converter, 14... Output voltage characteristic line at initial stage, 15...
Output voltage characteristic line after the elapse of time, 16... Solenoid valve,
17... Adder, 18... Controller, 19...
・Signal line, adjustment...control line, 21...feedback line, ρ...correction characteristic line, n...offset voltage change curve over time of conventional air micrometer, dying... 3 is a curve of offset voltage over time in an air micrometer equipped with a correction device according to an embodiment of the present invention. Agent Patent Attorney Tadashi Akimoto MitsudateFigure 1Figure 2Figure 3Figure 4

Claims (1)

[Claims] A reference differential pressure chamber facing the fixed gap forming tool through a nozzle, a measurement differential pressure chamber facing the object to be measured through a nozzle, and both of the above differential pressure chambers are communicated through the nozzle, respectively. a pressure difference between the supplied supply chamber, an air pipe line for supplying air at a certain pressure to the supply chamber, and both differential pressure chambers, and output an electrical signal proportional to the pressure difference.・Equipped with a pressure transducer, a solenoid valve is interposed and connected in the air pipe line, and an adder is interposed in the output circuit of the differential pressure converter. and a function of storing the value of the output electric signal, a function of performing calculation based on the stored value, a function of providing the result of the calculation to the adder, and the function of the electromagnetic valve. By providing a controller with a function of opening and closing,
An air micrometer equipped with a correction device, characterized in that it is capable of automatically correcting zero point movement caused by temperature characteristics of the differential pressure converter.