JPH02232541A - Pressure measuring apparatus - Google Patents

Abstract

PURPOSE:To facilitate a calibration by a method wherein a correction data is prepared to be stored and four areas containing a measured value are detected to a perform a corrective computation. CONSTITUTION:A setting section 12 and a display section 13 are mounted externally at a body section 1a to form a pressure measuring device 1. Then, the body section 1a is housed in a thermostatic cell 20 and a temperature is set to T1. A pressure is inputted from an external pressure generation source 2 varying a pressure range from a minimum value P1 and a maximum value Pn by stages and the current pressure display value is stored at an input address of a nonvolatile memory 18 set with a setting section 12. Thereafter, the temperature of the thermostatic cell 20 is varied to T2...Tn and an input pressure to P1...Pn to prepare a correction data. When an actual pressure is measured, a device 2 to be measured is connected to a pressure sensor 3 to measure the input pressure and a temperature is measured with a temperature sensor 4. Then, a CPU 10 checks to see to which of adjacent four areas of the correction data the measured value belongs and performs a corrective computation by the data in the area detected. In this manner, a true pressure can be calculated to be shown on a display section 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a pressure measuring device used to calibrate equipment such as pressure transducers and pressure switches used in industrial processes.

(Example) Conventional technology A semiconductor pressure sensor is often used as a pressure sensor in a pressure measuring instrument for calibration. Since the characteristics of a semiconductor pressure sensor are affected by temperature, a pressure measuring device is provided with a separate temperature sensor to detect the temperature and perform correction according to the temperature. FIG. 7 shows a specific example of this type of pressure measuring device. This pressure measuring device 1 includes a pressure sensor (semiconductor pressure sensor) 3 to which a pressure signal from an atlI regulator 2 is manually input, and a temperature sensor to detect ambient temperature. A signal amplifier 5 that increases the outputs of the sensor 4, pressure sensor 3, and temperature sensor 4
, 6, a multiplexer 7 that time-divisionally outputs the outputs of the signal amplifiers 5 and 6, and an A/D converter 8 that converts the pressure signal and temperature signal output from the multiplexer 7 into digital values.
, PROM that stores correction data for pressure and temperature in advance.
9. Based on the pressure and temperature data taken in from the A/D converter 8, refer to the correction data in the PROM 9, and input the CPUIO that corrects the true value, the RAM II for calculation, and commands for unit and range switching. Setting section I2, display section 13 that displays true values, printer 14, CPUIO and setting section I2
, a display section 13, an interface section 15 that connects a printer 14, and the like.

In this pressure measuring device, the temperature characteristics of the output pressure with respect to the input pressure are determined in advance, and the FROM9 is used as correction data.
I remember it. During actual pressure measurement, as shown in FIG.
, and the temperature T at that time is measured by the temperature sensor 4 (stenob STl). Then, a correction interval is determined from this temperature T (step ST2), and the pressure is calculated with reference to the correction data in FROM 9 (stenob ST3). and,
The pressure is displayed on the display section I3 (Ste Nobu ST
4).

(c) Problems to be Solved by the Invention When a pressure sensor used in a pressure measuring device is used for a long time, its static characteristics and temperature characteristics change depending on the pressure sensor itself, how the pressure sensor is installed, etc. In this case, temperature characteristic data for correction is stored in FROM as in the conventional pressure measuring instrument mentioned above.
If the temperature characteristics are stored in the FROM, the temperature characteristics must be taken again from scratch and rewritten in the FROM, and the user cannot easily calibrate on site and must request recalibration from the manufacturer. Therefore, there was a problem in that recalibration required a large amount of cost and time.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a pressure measuring instrument that is easy to calibrate and can perform precise temperature correction even when characteristics change.

(2) Means and Effects for Solving the Problems The pressure measuring instrument of the present invention includes a pressure sensor, a temperature sensor, a signal amplifier for amplifying the signals of the pressure sensor and temperature sensor, and a digital output of the signal amplifier. an A/D converter for converting into a signal; a setting section for inputting commands such as units and ranges; and an arithmetic control section for performing correction calculations on the detected pressure based on the temperature signal detected by the temperature sensor; and a display section for displaying the pressure value set, wherein the setting section and the display section are configured to be in contact with the main body,
Combinations of reference input pressures and points with different values and their corresponding pressures. A non-volatile memory that stores a plurality of data of force measurement values at an address designated by the setting section, and a nonvolatile memory that stores a plurality of data of force measurement values at an address specified by the setting section, and a memory that stores a plurality of data of force measurement values at an address specified by the setting section, and a memory that stores a plurality of force measurement data at an address specified by the setting section; It is characteristically equipped with an area detecting means for detecting whether the area is included in the head area of the head, and a correction calculation means for correcting the measured value based on the four pressure data of the detected area and calculating the true pressure value.

With this pressure measuring instrument, various temperatures T,...
, T. Input pressure P, which becomes the reference for each stage,...
P. and enter each measured pressure as P. ,...,P
o, and these data are stored in advance as correction data (FIG. 4) in a non-volatile memory such as IE-ROM.

Next, when actually measuring pressure, input pressure PL is added to obtain measured value PXy. Then, it is detected which of the regions surrounded by four adjacent correction data this measured value P This is calculated and displayed on the display.

When recalibrating, the temperature 'r1, . . . shown in FIG.
・、T. and the input pressure Pl,...,P, are input in sequence, and the measured value P11,...,I),7
is sequentially stored in the nonvolatile memory address set by the setting section.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a block diagram of a pressure measuring device showing an embodiment of the present invention. In this embodiment, the same numbers as those of the pressure measuring device shown in FIG. 7 indicate the same components. The features of the pressure measuring instrument 1 of this embodiment are that the main body 1a
In contrast, the setting section 12 and display section 13 are externally attached, and can be connected and removed using cables 16 and 17. Furthermore, the main body 1a also includes an addressable nonvolatile memory (for example, EE-ROM) 18.

When calibrating this embodiment of the pressure measuring instrument,
As shown in Fig. 2, the pressure measuring device main body la is
The pressure is inputted from the outside from a pressure generation source 21. Then, the temperature of the constant temperature layer 20 is set to T, and the input from the pressure generation source 2l is divided from the minimum to the maximum input pressure range, and the pressure is changed stepwise by PI, ..., P7, and then The output value (display value) is stored in the input address of the EEROM 18 set by the setting section 12 (see FIG. 4).
Thereafter, the temperature of the constant temperature layer 20 is changed to T2, . . . , T7, and the input pressure is changed to P l s .

A specific example of this calibration procedure will be explained with reference to the flow diagram shown in FIG.

When the calibration starts, first, the temperature of the constant temperature layer 20 is set to T [step ST (hereinafter abbreviated as ST) l1]. Then, the input pressure from the pressure generation source 21 is set to P1 (S
T12). Next, press the calibration key on the setting section 12 and display 1.
Measure the pressure P and temperature T generated in the section 13 (ST
13). Write the measurement results pressure P and temperature T into memory (STI4). Next, it is determined whether the input pressure P, is the maximum (ST15), and if it is not the maximum, the input pressure P7 is changed in ST16. In other words, step from P+ to P2. Then, press the calibration key on the setting device l2 again and press the pressure P.
and temperature T (STI3), and the measurement result pressure P
and temperature T are written in the memory (ST14). The above processing is assumed to be temperature T, and input pressure P + , P z ,...
・The processes of ST13 and ST14 are repeated until the maximum value P7 is reached, and the manual pressure Pl%P2 at temperature T1, ・
...Write each measurement result for Pfi into memory. When the input pressure reaches the maximum value, the determination in S715 is YE.
Then, in ST17, it is determined whether the temperature is at the maximum. Since the initial temperature T, is not the maximum, the process moves to STI8 and the temperature T. ,change. In other words, change from T1 to T2 and ST12
Return to and repeat ST12 to ST15 to reduce the pressure to P.
, to P7, and the measurement result P each time is
, T to memory. Thereafter, the steps STII to ST15 are repeated until the temperature reaches T, . The temperature reaches the maximum temperature T7, and the input pressure also reaches the maximum pressure P. The measurement results P, are written in the memory until . When the temperature reaches the maximum, the determination in ST17 ends with YES, and the calibration ends. As a result, the input pressure P + shown in FIG.
..., output pressures P I1, ..., P,, R corresponding to Pn, temperatures T', ..., T7 can be obtained. Next, an explanation will be given of the operating procedure when actually measuring pressure using the calibrated example pressure measuring device as described above. First, when the input pressure is measured with the device under test 2 connected to the pressure sensor 3, and the measured value is set as PXy, and the temperature T detected by the temperature sensor 4 is further measured, this pressure p x, , temperature T But which of the four adjacent pressure data ranges in Figure 4? CPUIO
will investigate. In the example shown in FIG. 4, P2■, P32, ・p
zz, indicating that it is included in P33. It is assumed that this relationship is as shown in FIG. Furthermore, if the 11 values of the measured pressure P xy are PL, then PZ'l, Po
What is the straight cotton A passing through? Straight line B passing through force and pressure P2■, P3Z
becomes.

The point where true value P1 and straight line 8 intersect is yt, true value P, and straight line B
Letting the intersection point be yl, we get the following.

Therefore (yz −3'+ ): ('ri
-72)'=(PL)'l):
(T Tz ), and from these two, T, -T, T-TZ Therefore, the true value pressure P, becomes. The calculated PL of equation (1) is displayed as the true value on the display section l3.

Therefore, the measurement procedure is as shown in Figure 6.
Pressure P my input from the device under test 2 to the pressure sensor 3
is first measured, and then the temperature T in that state is measured (S
T21). Next, four pieces of calibration data including this measured pressure ptiy are detected (ST22). Four pieces of data detected. is substituted into (1) 2 of P, described above, and the true value Pt is calculated (ST23). Display section I3
(ST24). As described above, even if the temperature changes, the correct pressure can be measured with high precision.

In addition, in the above implementation and example pressure measuring instrument, the pressure sensor 3
If the relationship between temperature and input pressure changes significantly due to changes in the characteristics of the measurement system, including aging, recalibration may be performed. When recalibrating, the pressure measuring device is placed in the constant temperature chamber 20 as shown in Figure 2 according to the calibration procedure described above, and the temperature and input pressure are gradually adjusted step by step according to the same calibration procedure as explained at the beginning. Switch the data as shown in Figure 4 to E.
Just rewrite to E-ROMI 8. The address to be rewritten is input using the setting unit 12.
Therefore, once the address has been set, recalibration values can be easily registered, making it possible to always perform accurate measurements.

(F) Effects of the Invention According to this invention, the setting section and the display section are connected to the main body.
Since it is configured so that it can be connected and disconnected freely, when it is placed in a constant temperature chamber and recalibrated by changing the pressure and temperature, settings can be made from the outside and the display can be checked. Moreover, temperature measurement stores the manual pressure and a pair of output pressures corresponding to the temperature in a non-volatile memory, and based on these correction data, determines the area where the output pressure is included in four different data. Since it extracts data and performs correction calculations based on the four pieces of data in the extracted area, it is possible to always measure the correct true pressure.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a pressure measuring device showing an embodiment of the present invention, Fig. 2 is a schematic explanatory diagram for calibrating the same pressure measuring device, and Fig. 3 is a calibration procedure for the same pressure measuring device. FIG. 4 is a flowchart showing the manual pressure stored in the EE-ROM of the pressure measuring device and an output pressure table corresponding to temperature. FIG. 5 is a flowchart showing the pressure in the pressure setting device of the same embodiment. A characteristic diagram for explaining the measurement principle, FIG. 6 is a flow diagram showing the measurement procedure of the pressure measuring device of the same embodiment, FIG. 7 is a process diagram showing the conventional pressure measuring device, and FIG. It is a figure which shows the measurement procedure of the pressure measuring device. 1: Pressure measuring instrument, la: Pressure measuring instrument body, 3: Pressure sensor, 4: Temperature sensor, 5/6: Signal amplifier, 8: 8/D converter, 10: CPU, 12: Setting section, 13: Display section, 18: EE-ROM. Patent applicant: Shimadzu Corporation Representative: Patent attorney: Shigeru Nakamura

Claims (1)

[Claims] (1) a pressure sensor, a temperature sensor, and the pressure sensor;
a signal amplifier that amplifies the signal of the temperature sensor; an A/D converter that converts the output of the signal amplifier into a digital signal;
A setting section for inputting commands such as units and ranges, an arithmetic control section for performing correction calculations on the detected pressure based on the temperature signal detected by the temperature sensor, and a display section for displaying the corrected pressure value. In the pressure measuring instrument, the setting section and the display section are configured to be able to be moved into and out of the main body section, and a plurality of data of combinations of reference input pressures and temperatures having different values and pressure measurement values corresponding thereto are displayed. A non-volatile memory is stored at an address specified by the setting section, and during actual pressure measurement, it is detected in which region of the plurality of data surrounded by four adjacent pressure data the measured value is included. A pressure measuring instrument characterized by comprising: area detection means; and correction calculation means for correcting a measured value based on four pressure data of the detected area and calculating a true pressure value.