JP2550735B2 - Measuring instrument with adjustment invalidation function - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention is mainly used in industrial measurement fields and uses a measuring instrument using a microcomputer (for example, a capacitance type pressure measuring instrument).
In particular, the present invention relates to a measuring instrument with an adjustment invalidation function, which has a function of invalidating the adjustment switch in order to prevent erroneous operation of the weighing adjustment switch.

[Prior art]

As a measuring instrument used in the industrial measuring field, for example, as a pressure measuring instrument, in the case of an analog circuit as an adjusting function,
There is known one provided with a zero adjustment switch using a trimmer and the like, and a span adjustment switch.

[Problems to be Solved by the Invention]

Many of the adjustment switches described above have a structure that can be adjusted from the outside of the measuring instrument for ease of adjustment. For this reason, these adjustment switches cause human malfunctions in addition to normal adjustment. In some cases, incorrect adjustment was made due to factors such as the above, and the current output of 4 to 20 mA, etc. corresponding to the input was shifted. Further, if it is structurally adjustable from the outside, there is a risk that it will be adjusted unnecessarily. Therefore, in order to solve the above-mentioned problems, the present invention provides a measuring instrument with an adjustment invalidation function, which is structurally provided with a switch that can be adjusted from the outside, but which is capable of avoiding adjustment due to human error or the like. It is an issue.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the measuring instrument of the present invention is an “A / D conversion unit (A / D converter 12 or the like) for converting an analog amount which changes depending on the measured amount into a digital value, and the measured amount. D / to get the corresponding current output signal
A conversion means (such as the D / A converter 14), and the calculated amount is calculated from the digital value output from the A / D conversion means, and further, in accordance with the measured amount.
A microcomputer (13, etc.) that calculates and outputs the digital value given to the D / A conversion means, a mode setting switch (Digi SW15, etc.) that switches and sets the operation mode of this microcomputer, and a 0-point adjustment mode for this mode setting switch. And 100
A measuring instrument provided with a correction amount increase / decrease switch (UP SW16, DOWN SW17, etc.) for increasing / decreasing the correction amount for the measured amount in the state of being set to the% point adjustment mode, So that the operation mode of the microcomputer that disables the operation of the correction amount increase / decrease switch (designates the lock function) can be set by the mode setting switch (such as setting the position number to "2") " I shall.

[Work]

A position to set the lock function is provided in the digital switch that sets the operation mode of the microcomputer, and when the digital switch is set to this position, the UP switch, DOW that increases or decreases the correction amount for the detection amount in zero adjustment and span adjustment.
The function of the N switch is disabled.

【Example】

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 and FIG. FIG. 2 is a block diagram showing the configuration of a pressure measuring device as an embodiment of the present invention. In the figure, 1 is a pressure measuring instrument, 2 is a DC power source, 3 is an output current 4 of the pressure measuring instrument.
It is a voltage conversion resistor of 250Ω that converts -20mA to 1-5V. This pressure measuring device converts the measured pressure value to a current value of 4-20mA and outputs it. Pressure measuring device 1 is a pressure detector
11, an A / D converter 12 that digitally converts the detection signal of the detection unit 11, a microcomputer 13 that obtains pressure from the output data of the A / D converter 12, and outputs current data corresponding to this pressure value, this microcomputer 13 It is composed of a D / A converter 14 and the like that converts the output data of the above into a current value for D / A conversion. In the pressure measuring device 1, the electrostatic capacitances C1 and C2 change corresponding to the pressure received by the pressure detection unit 11, and these electrostatic capacitances C1 and C2 are converted into pulse widths by the A / D converter 12, respectively. To do. The microcomputer 13 counts these pulse widths with a clock as a reference, and the electrostatic capacitances C1, C as physical quantities.
Detect sampling data proportional to 2, calculate the detected pressure value based on this sampling data, and calculate the data to be given to the D / A converter 14 to obtain the current output corresponding to this detected pressure value. And output. Then, the D / A converter 14 performs D / A conversion corresponding to the operation output data of the microcomputer 13 to output 4 to 20 mA.
To produce. By the way, the microcomputer 13 has a function setting digital switch (hereinafter, the switch is also abbreviated as SW) for adjustment. In this example, the digital switch 15 is an input switch for 3 bits (3 pieces), and 2 ³ = 8, that is, it is possible to switch eight positions from position numbers 0 to 7), and UP SW16 and DOWN SW17 are connected. FIG. 1 shows an example of function assignment by position number of the digital switch 15. The number of positions will be described here as eight positions, but there is no particular need to have eight positions. The function corresponding to each position number can be set by software of the microcomputer, which will be described with reference to FIG. 2 as an example. Position number "0" has the function of zero adjustment,
When 15 is set to this position, 0% of the reference input pressure is applied, in other words, the capacitance C of the pressure detection unit 11 is
With the pressure applied to both sides of C1 and C2 equal, press UP SW16
Alternatively, pressing the DOW-N SW17 increases or decreases the correction value for the pressure value detected by the microcomputer 13, respectively, and as a result, the output value of the microcomputer 13 at this zero point (indicated by the digital indicator or D / A The current output from the converter 14) goes up or down. Similarly, position number "1" is a span adjustment function, and when the digital switch 15 is set to this position, 100% of the reference input pressure is applied, in other words, the capacitance C1 side of the pressure detector 11. UP SW16 with a pressure difference of 100% between C2 and C2
Or output of 100% point is UP or DOWN by operating DOWN SW17. The position number "2" is the setting position of the lock function, which is the main feature of the present invention, and when the digital switch SW15 is set to this position, the UP SW16 and DOWN SW17 are disabled and adjustment due to erroneous operation is prevented. In a digital circuit that uses a microcomputer, the PV value (that is, Process Varia) based on the detection value of the input side A / D converter 12
ble: In this example, calculate the pressure detection value) and set the output current.
The functions of the D / A converter 14 can be operated independently. In the position numbers "3", "4", and "5" of the digital switch 15, constant current output is set in this way regardless of the PV value of the input, and current output of 4 mA, 12 mA, 20 mA is performed respectively.

【The invention's effect】

As described above, according to the present invention, the measuring instrument including the digital SW 15 and using the minecon 13 has the following software.
It is possible to operate the function corresponding to the position of this Digi SW15. The lock (adjustment invalidation) function is provided in one of these positions, and the operation of the external adjustment SW is invalidated by setting the Digi SW15 to this position. Since it is obtained, it is possible to prevent erroneous adjustment of the measuring instrument due to erroneous operation of the external adjustment switch.

[Brief description of drawings]

FIG. 1 is a diagram showing a function assignment according to positions of a digital SW as an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a pressure measuring device according to the present invention. 1: Pressure measuring device, 2: DC power supply, 11: Pressure detector, 12: A / D converter, 13: Microcomputer, 14: D / A converter, 15: Digi-S
W, 16: UP SW, 17: DOWN SW.

Claims (1)

(57) [Claims] 1. An A / D conversion means for converting an analog quantity, which changes depending on the quantity to be measured, into a digital value, and a D / A for obtaining a current output signal corresponding to the quantity to be measured.
The conversion means, the digital value output from the A / D conversion means is calculated by obtaining the measured amount, further D / corresponding to the measured amount
A microcomputer that calculates and outputs the digital value given to the A conversion means, a mode setting switch that switches and sets the operation mode of this microcomputer, and a 0 point adjustment mode and 100%
A measuring instrument comprising a correction increase / decrease switch for increasing / decreasing a correction amount for the measured amount in the state of being set to the point adjustment mode, wherein the operation of the correction amount increasing / decreasing switch is invalidated. A measuring instrument with an adjustment invalidation function, wherein the operation mode of the microcomputer can be set by the mode setting switch.