JPH04323568A - Analogue measuring circuit - Google Patents

Abstract

PURPOSE:To shorten the time required for adjusting circuits so as to prevent generation of errors in measurement by adjusting and storing the control data of the analogue input signal of a set value and any error in measurement using a CPU, and processing a signal for measurement using the stored data. CONSTITUTION:An analogue input signal is converted by an A/D converting circuit 5 using the voltage of a reference voltage generating circuit 4 as a reference, and has its signal level measured. The mode of this measuring circuit can be set in such a way as being switched from a correction mode to a measuring mode or vice versa. At the correction mode a control data value fed to the circuit 4 in such a way that the output signal of the circuit 5 is converted to a preset value according to the analogue signal of the preset value is adjusted by a CPU 6 and its data and any error in measurement are stored in an internal memory. At the measuring mode the circuit 4 is adjusted on the basis of this control data and A/D conversion is performed and according to any stored error in measurement the digital signal of the measurement is corrected. The time required for adjusting the circuits is thus shortened so as to reduce the cost and also to prevent generation of errors even if nonlinearity arises.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an analog measurement circuit capable of accurately and automatically correcting measurement errors in each of a plurality of ranges.

0002

[Prior Art] Analog measurement circuits that measure voltage values of analog signals generally switch between multiple ranges to perform measurements over a wide range.
A circuit shown in FIG. 3 is known.

The analog measurement circuit shown in this figure includes an attenuator 101 that attenuates an input signal, a full-wave rectifier circuit 102 that rectifies the output signal, and a full-wave rectifier circuit 102 that rectifies the output signal.
Amplifier circuit 1 that adjusts the magnitude of the DC signal output from
03, a reference voltage generation circuit 104 that generates a reference voltage, the value of the reference voltage outputted from this reference voltage generation circuit 104, and the DC signal outputted from the amplification circuit 103, which are A/D converted (analog/digital conversion). ), for example “
A/D conversion circuit 1 that generates an 8” bit digital signal
05.

When measuring the voltage of an analog input signal, it is common to first select an appropriate range depending on the signal level to be measured and perform correction based on the reference level prior to this measurement operation.

For example, to illustrate the case of setting AC100V full scale, first input an accurate AC100V to the input section of the attenuator, and then set the attenuator 101 to
and adjusts the amplifier circuit 103 so that the output of the A/D conversion circuit 105 becomes the highest value of 255 of 8 bits.

In this example, the means for digitally converting the DC voltage is to compare the input voltage Vi with a reference voltage of 5V, and in this case, the output voltage Vi of the amplifier circuit 103 is adjusted to be 5V. conduct.

After this adjustment operation is completed, an analog input signal to be measured is input to the attenuator 101, and the A/D conversion circuit 105 converts it into a digital signal, which is then used in the next stage circuit such as a display device (not shown). (omitted).

However, in such a conventional analog measuring circuit, it is necessary for an operator or the like to adjust the attenuator and the amplifier circuit 103, which not only takes time but also depends on the characteristics of the analog circuit. As shown, an attenuator 101 and an amplifier circuit 103
There is a problem in that the DC signal output from the sensor may become nonlinear within a certain voltage range, and the error at this time directly appears as a measurement error. Such errors vary depending on the set range, and it is difficult to uniformly correct them.

[0009]

[Object of the Invention] In view of the above circumstances, the present invention is capable of shortening the time required for circuit adjustment and reducing costs, and also prevents measurement errors from occurring even if a nonlinear portion occurs in an analog circuit portion. The purpose is to provide an analog measurement circuit that can perform

0010

SUMMARY OF THE INVENTION In order to achieve the above object, an analog measuring circuit according to the present invention uses a reference voltage output from a reference voltage generating circuit as a reference when an analog input signal is input. In an analog measurement circuit that converts an analog input signal into a digital signal and outputs it, when the correction mode is set, the digital signal obtained by inputting the analog input signal of a preset value to the A/D conversion circuit A measurement section that adjusts the value of control data supplied to the reference voltage generation circuit so that the signal becomes a preset value, and also stores the control data and measurement error at this time, and a measurement mode is set. When the control data obtained by the measurement section is supplied to the reference voltage generation circuit to adjust the A/D conversion circuit to convert the analog input signal to be measured into a digital signal, The present invention is characterized by comprising a control correction section that corrects the digital signal based on a measurement error obtained by the measurement section.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on embodiments shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of an analog measuring circuit according to the present invention.

The analog measurement circuit shown in this figure includes an attenuator 1, a full-wave rectifier circuit 2 that converts the output into DC, an amplifier circuit 3 that converts the DC value into a specified value, a reference voltage generation circuit 4, and a An A/D conversion circuit 5 that digitally converts the signal under test using the signal from the reference voltage generation circuit 4, and a CP
U6, and it is possible to switch between two modes: correction mode and measurement mode. When the correction mode is set, the CPU 6 controls the CPU 6 so that the value of the digital signal output from the A/D converter circuit 5 becomes the preset value when an analog input signal with a preset value is input.
adjusts the reference voltage generation circuit 4 and stores the control data at this time, and when the measurement mode is set, the CPU 6
The reference voltage generating circuit 4 is adjusted based on the control data stored in the attenuator 1, and the analog input signal input to the attenuator 1 is converted into a digital signal, which is then sent to the next stage circuit (
(not shown).

When an analog input signal is input, the attenuator 1 attenuates the analog input signal and supplies it to the full-wave rectifier circuit 2 . The full-wave rectifier circuit 2 performs full-wave rectification on the analog input signal output from the attenuator 1 to convert it into a DC signal, which is then supplied to the amplifier circuit 3 . The amplifier circuit 3 adjusts the magnitude of the DC signal output from the full-wave rectifier circuit 2 with a set amplification factor and supplies it to the A/D conversion circuit 5. The reference voltage generation circuit 4 generates a reference voltage according to the control data output from the CPU 6 and supplies it to the A/D conversion circuit 5. A/
The D conversion circuit 5 performs A/D conversion (analog/digital conversion) of the DC signal output from the amplifier circuit 3 using the value of the reference voltage output from the reference voltage generation circuit 4 as a reference value, and converts it into, for example, "8" bits. generates a digital signal and converts it to CP
Supply to U6. The CPU 6 includes a microprocessor that performs various processes, a ROM that stores programs that define the operations of this microprocessor, a RAM that is used as a work area for the microprocessor, and control data obtained by the microprocessor. It is equipped with a non-volatile memory etc. in which the data is stored, and when the correction mode is set, the value of the digital signal output from the A/D conversion circuit 5 is adjusted while controlling the reference voltage generation circuit 4. After controlling the reference voltage generation circuit 4 based on the control data stored in the nonvolatile memory when the measurement mode is set, the A/D conversion circuit 5 It captures the digital signal output from the circuit and outputs it to the next stage circuit.

Next, the correction operation and measurement operation of this embodiment will be sequentially explained with reference to FIG.

First, when the correction mode is set, the input to the attenuator 1 is set to, for example, an AC signal of "99.6V", and the CPU 6 outputs the A/D conversion circuit 5.
Adjust the value of the control data supplied to the reference voltage generation circuit 4 so that the value of the digital signal output from the reference voltage generation circuit 4 becomes "255", and adjust the value of the reference voltage output from the reference voltage generation circuit 4. After that, the control data currently being supplied to the reference voltage generation circuit 4 is written into the internal nonvolatile memory.

At this time, in order to correct the nonlinearity of the amplifier circuit 3 and the attenuator, several voltage values are selected in the range of "0V to 100V" and the AC signal corresponding to each of these voltage values is applied to the attenuator. 1, and the value of the digital signal output from the A/D conversion circuit 5 at this time is CP.
The deviation from the theoretical value is taken in by U6 and measured as shown in FIG. 2, and these deviations are written into the nonvolatile memory as correction values.

Therefore, for example, when 80V is input in the correction mode, the theoretical value is 204, whereas the AD conversion value is 209.The correction value of the AD conversion value 209 is set to -5 and is written in the memory.

After this, when the measurement mode is set, the CP
U6 reads out the control data written in the internal non-volatile memory and supplies it to the reference voltage generation circuit 4, which causes the reference voltage generation circuit 4 to output a reference voltage according to the control data. After that, when the analog input signal to be measured is input to attenuator 1, C
The PU6 takes in the value of the digital signal output from the conversion circuit 5 and outputs it to the next stage circuit, but at this time,
Corresponding to the value output from the A/D conversion circuit 5, a correct measured value is output based on the above-mentioned correction value.

Therefore, for example, in the measurement mode, the 20
When a converted value of 9 is obtained, 204 is obtained by adding -5, which is the stored content of the nonvolatile memory.

At this time, a plurality of correction values stored in the non-volatile memory are linearly interpolated to create correction data for the digital signal value, and the output signal value from the A/D conversion circuit 5 is corrected based on this correction data. This corrects nonlinear distortion in analog circuits, etc.

As described above, in this embodiment, the reference voltage outputted from the reference voltage generation circuit 4 is adjusted so that the value of the digital signal outputted from the A/D conversion circuit 5 becomes a predetermined value prior to the measurement operation. By adjusting the value of , storing the control data at this time, and performing measurement, the time and effort required for circuit adjustment can be significantly saved, and the cost required for circuit adjustment can be reduced.

In the above embodiment, A for each prescribed input is
Although the case where the difference between the /D conversion output value and its standard value is stored is shown, the case is not limited to this, and the case where the A/D conversion circuit output itself for each specified input or the control signal itself to be input to the reference voltage generation circuit can be input. It is also possible to store the results as a table of outputs and output the measurement results based on the table.

[0024] Also, among the correction values written in the nonvolatile memory, the value of the digital signal is corrected using the correction value that is closest to the value of the digital signal obtained by the measurement operation. Also good.

In the above-described embodiment, the voltage value of the analog input signal is measured, but other analog signals such as current value, magnetic flux density, etc. may also be measured.

Furthermore, in the correction mode, it is possible to create a correction value that takes into account not only non-linear distortion but also temperature conditions, thereby correcting measurement errors due to temperature changes.

[0027]

[Effects of the Invention] As explained above, according to the present invention, it is possible to shorten the time required for circuit adjustment and reduce costs, and measurement errors occur even if a nonlinear portion occurs in a certain voltage range. You can prevent it from happening.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of an analog measurement circuit according to the present invention.

FIG. 2 is a table showing an example of the operation of the analog measuring circuit shown in FIG. 1;

FIG. 3 is a block diagram showing an example of a conventionally known analog measurement circuit.

FIG. 4 is a table showing an example of the operation of the analog measuring circuit shown in FIG. 3;

[Explanation of symbols]

1 Attenuator 2 Full wave rectifier circuit 3 Amplification circuit 4 Reference voltage generation circuit 5 A/D conversion circuit

Claims (3)

[Claims] 1. Analog measurement in which, prior to measuring an analog signal level, the analog input signal is converted into a digital signal by an A/D conversion circuit using a reference voltage output from a reference voltage generation circuit as a reference and output. In the circuit, when the correction mode is set, the standard is set such that the digital signal obtained by inputting an analog input signal of a preset value to the A/D conversion circuit becomes the preset value. A measurement unit that adjusts the value of control data supplied to the voltage generation circuit and stores the control data and measurement error at this time, and a measurement unit that stores the control data obtained by the measurement unit when the measurement mode is set. Supplying the reference voltage to the reference voltage generation circuit and adjusting the A/D conversion circuit to convert the analog input signal to be measured into a digital signal, and correcting the digital signal based on the measurement error obtained by the measurement section. An analog measurement circuit characterized by comprising a control correction section that performs the following steps. 2. An analog measurement circuit having a function of switching to a desired range before measuring an analog signal level, comprising a reference voltage generation circuit that generates a plurality of reference voltages for each range, and a correction mode. means for applying the reference voltage to the input terminal of the measuring circuit and switching to the plurality of reference voltages for each range; and means for storing an error value for each reference voltage; . An analog measuring circuit characterized in that a measured value for an input signal is corrected based on the stored error value. 3. Prior to measuring the analog signal level, in an analog measurement circuit that has a function of switching to a desired range and includes means for A/D converting the signal under test, a correction mode is set for each range. At the time of setting, a plurality of signals of specified levels are input to the input of the measuring circuit, and a reference signal to be used in the A/D conversion means is generated so that the A/D conversion output for each signal becomes a specified value. , either the reference signal value or the difference between the reference signal value and the standard value is memorized, and in the measurement mode, it is possible to measure or correct the measured value based on the memorized content. Characteristic analog measurement circuit.