JPH01307801A - Measuring instrument having automatic adjusting function - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention compares a measured value supplied from the outside, such as a controller, with a target value that is input and set in advance, and based on the comparison result, The present invention relates to a meter having an automatic adjustment function that automatically adjusts an output analog output value.

[Prior Art] Taking a controller as an example of this type of instrument, a controller compares a measured value supplied from the outside with a target value that is input and set in advance, detects the difference, and calculates the detected result. Follow-up control is performed based on the measured value so that it approaches the target value.

In order to perform this kind of follow-up control, in conventional controllers, the output value that is converted from a digital value to an analog value is adjusted using a trimmer resistor connected to an amplifier installed in the output stage of the meter. This was done by changing the value. That is, this trimmer is equipped with a zero point (lower limit) setting resistor and a span point (upper limit) setting resistor, and can be adjusted by varying these setting resistors depending on the measurement range.

[Problems to be Solved by the Invention] However, with the advancement of digital equipment, in the digital equipment equipped with a CPU that has an analog output value and is used today, when the adjustment method using the trimmer described above is applied, the resolution of the trimmer is In addition to causing adjustment errors due to individual differences, the adjustment value changes depending on physical conditions such as vibration, which causes problems such as a lack of stability, reproducibility, and reliability in adjustment. I was not able to show my full potential.

In addition, since the adjustment value changes depending on the conditions mentioned above,
There was a problem in that adjustments using the trimmer had to be made repeatedly as necessary.

Therefore, the present invention has been made in view of the above-mentioned problems, and its purpose is to reduce the number of adjustment steps by eliminating the need for repeated adjustments as in the past, and to provide stable adjustment performance through digital adjustment using a trimmer-less system. The purpose of the present invention is to provide an instrument that has high accuracy, reproducibility, and reliability, and has an automatic adjustment function that can fully demonstrate the inherent merits of digital technology.

[Means for Solving the Problems] In order to achieve the above object, a meter having an automatic adjustment function according to the present invention is a meter having a function of converting a digital value into an analog value at a predetermined level and outputting the converted value.

A configuration in which a digital value corresponding to the analog value is measured, an error is calculated by comparing the measured digital value and an expected value of the digital value, and the analog value is adjusted based on this error. It is characterized by becoming.

[Operation] When a digital value corresponding to an analog value output from a meter is measured, this measured digital value is compared with an expected value of this digital value, and a correction value as an error is calculated. Then, the analog value is adjusted and output based on the calculated correction value.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a meter having an automatic adjustment function according to the present invention.

The instrument according to this embodiment is made by focusing on the point that the analog output characteristic basically depends linearly on the digitally determined output characteristic. Compare with the set target value,
Based on this comparison result, follow-up control is performed so that the measured value approaches the target value, and the output value is automatically adjusted. It is configured.

The measurement unit 1 includes thermocouples, temperature resistance resistors, DC voltages, and DC voltages corresponding to physical quantities such as temperature, humidity, pressure, and flow rate that are actually controlled in external (electric furnaces, firing furnaces, air conditioners, etc.) controlled objects. Any of the currents is taken in as an input signal, and this taken-in signal (analog signal) is converted into a digital signal and output to the processing part 5 of the measurement adjustment part 4.

The processing section 5 corrects the signal supplied from the measuring section 8 based on correction values stored in the memory section 7, which will be described in detail later, and outputs the corrected signal to the converting section 3.

The setting unit 2 sets a control pattern for a controlled object controlled using a predetermined adjustment method (for example, PID method), and also sends a command signal for adjusting the output value so that the measured value follows the target value. is output to the processing unit 5, and the settings at that time are performed, for example, while visually checking the display screen based on key operations.

The converter 3 includes a D/A converter and an amplifier, and converts the digital value supplied from the processor 5 into an analog value (voltage or current value) at a predetermined level and outputs the analog value.

The measurement adjustment section 4 includes a processing section 5 and a memory section 7 that are built into the same instrument 6 together with the above-mentioned measurement section 1, setting section 2, and conversion section 3, and a measurement section 8 that is provided separately from the instrument 6. It is composed of a calculation section 9.

The measuring section 8 measures the analog value of a predetermined level outputted from the converting section 3 and converts it into a digital value, and is composed of, for example, a digital multimeter. It is output to an electronic computer.

The calculation unit 9 compares the digital value supplied from the measurement unit 8 with the expected value of this digital value, that is, the digital value corresponding to the analog value that should originally be output by the conversion unit, and performs correction to adjust the output value. The value (error) is calculated, and the data based on the calculated correction value is, for example, E21'lOM
The information is written and stored in the memory section 7 of the computer.

Next, the operation of the instrument configured as described above will be explained.

In addition, in the operation shown below, two points (zero point, span point)
The explanation is given by taking as an example a case where output adjustment of an analog value is performed between the two.

When the processing unit 5 outputs digital values corresponding to the zero point and the span point to the converting unit 3, the converting unit 3 converts the digital values from D/A to output. Note that the analog values output at this time are AI and A2. and,
The measuring unit 8 receives the analog value A + output from the converting unit 3,
A2 is measured, converted into digital values DI and D2, and outputted to the calculation section 9.

The calculation unit 9 calculates the digital values D1 and D measured by the measurement unit 8.
2 and digital values D+' and D2' as expected values, respectively, and calculate a correction value for adjusting the output value.
That is, here Dl ′=a p 1 + b h
The correction values a and b are calculated by analyzing the simultaneous equations D2°=aD2+b, and the calculated correction values a and b are written and stored in the memory section.

Then, in the processing unit 5, the correction value a stored in the memory unit 7 is
, b, a correction process is performed on the measured value (digital value) from the measuring section 8, thereby allowing the converting section 3 to output the originally expected analog value.

By the way, in the embodiment described above, the correction values a and b for measuring the output value and adjusting the output value are calculated using a digital multimeter (measuring unit 8) that is configured separately from the meter 6 that forms the main body. Although this is configured to be performed by an electronic computer (computation unit 9), which is a device that has the function, if the above function is provided on the main body of the meter 6 (processing unit 5) as shown in Figure 2, information exchange with the outside will be possible. Automatic adjustment and calibration of output values can be performed by the instrument itself without the need for Furthermore, if the resolution of the D/A converter in the converting section 3 is increased at this time, it is possible to perform adjustment and calibration with a higher degree of configuration. Note that the processing section may have an arithmetic function for calculating the correction value, and only the measuring section for measuring the analog output value of the converting section may be provided separately from the instrument forming the main body.

Furthermore, in the above-mentioned embodiment, the analog output value at two points is measured and the correction formula for adjusting the output value is approximated by a linear formula. This makes it possible to deal with non-linear output value adjustment and configuration.

In addition, in the above embodiment, a controller was used as an example of a meter that adjusts and calibrates the output value, but it is also possible to use a meter that requires adjustment and calibration of the output value, such as a setting that outputs a set signal to an external device. The present invention can also be applied to a converter that converts an input signal to a predetermined level and outputs it, and in this case, the same effect as described above can be obtained.

[Effects of the Invention] As explained above, the instrument with the automatic adjustment function according to the present invention can adjust and calibrate the output value automatically and digitally using the feedback function, which is better than the conventional analog method. There is no need to perform reversal adjustment like with a trimmer, and the number of adjustment steps can be reduced. Therefore, the adjustment stability, reproducibility, and reliability are high, and the original advantages of digital can be fully demonstrated.

FIG. 2 is a block diagram showing one embodiment of the instrument; FIG. 2 is a block diagram showing another embodiment of the instrument having the same function.

1... Measuring section, 2... Setting section, 3... Conversion section, 4
...Measurement adjustment section, 5... Processing section, 6... Meter, 7
...Memory part, 8...Measurement part, 9...Calculation part.

Claims (1)

[Claims] In an instrument having a function of converting a digital value into an analog value at a predetermined level and outputting the converted value, a digital value corresponding to the signal converted to the analog value is measured, and the measured digital value is A meter having an automatic adjustment function, characterized in that the meter is configured to compare the expected value of the digital value and calculate the error thereof, and adjust the analog value based on this error.