JP2002135119A - Analog signal measuring method and measurement circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analog signal measuring method and a measurement circuit which enable expanding of a measuring range, without having to switch the range, even if the input signal goes out of the measuring range of an A/D converter. SOLUTION: A level comparison circuit 2, for outputting data in correspondence to an extent exceeding the measuring range, is connected to a differential amplifier 1 of which an input terminal is input by an analog input signal Si, and to a counter circuit 4, which performs up/down count, in correspondence to the output data. An analog voltage, in correspondence to the count result of the counter circuit 4, is generated by a D/A converter 5 and is input to another input terminal of the differential amplifier 1 and to an A/D converter 8 via an amplifier 3. Always values which do not exceed the level of the measuring range are input to the A/D converter 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog signal measuring method and a measuring circuit, and more particularly to an analog signal measuring method for an analog signal.
The present invention relates to an analog signal measurement method and a measurement circuit which enable measurement of an input signal exceeding the measurement range while keeping the measurement range of an A / D conversion unit when measuring by digitization by (analog-digital) conversion.

[0002]

2. Description of the Related Art When an analog signal is measured as digital data, an input analog signal is supplied to an A / A circuit through an amplifier circuit.
The signal is input to a D converter, and is processed using a digital signal obtained by the A / D conversion. FIG. 8 shows a conventional analog signal measuring circuit using an A / D converter. Input analog signal S
An A / D converter 202 is connected to the variable gain amplifier 201 that amplifies i, and an arithmetic processing unit 203 is connected to the A / D converter 202.

In FIG. 8, an input analog signal Si is subjected to a predetermined amplification by a variable gain amplifier 201, and then converted into a digital signal by an A / D converter 202. The digital signal is used in an arithmetic processing unit 203. Performs the voltage measurement. In this analog signal measuring circuit, when the input level (input voltage) of the analog signal Si changes, for example, from 0.1 V to 10 V, it is difficult to amplify such a wide range of voltage values without deteriorating the linearity. It is. If you measure in a state where linearity cannot be maintained,
Large errors will occur in the measured values. Therefore, processing for automatically changing the gain of the variable gain amplifier 201 according to the input level, that is, automatic measurement range switching is performed. In the automatic measurement range switching, the arithmetic processing unit 203 determines A / D conversion data, generates a control signal 204 based on the determination result, and controls the gain (amplification degree) of the variable gain amplifier 201 by the control signal 204. It is done by changing.

FIG. 9 shows the automatic measurement range switching of FIG.
For example, the amplifiable value of the variable gain amplifier 201 is set to -10
When V to +10 V, the measurement range is “× 1”, “×
10 "," x100 ", -10V to + 10V in the" x1 "range, and -1 in the" x10 "range.
V to + 1V, -0.1V to + in "x100" range
0.1 V is the measurable range. This range switching is performed by changing the degree of amplification of the A / D converter 202 by the arithmetic processing unit 203. The arithmetic processing unit 203 determines which measurement range the output of the A / D converter 202 is in. When the output is below the range currently used, the amplification of the variable gain amplifier 201 is increased, and , The variable gain amplifier 201 is controlled so as to lower the amplification degree.

[0005]

However, according to the conventional analog signal measuring circuit, the arithmetic processing unit 203 determines which measuring range the output of the A / D converter 202 is in, and based on the result, the variable range is determined. Since the gain amplifier 201 is controlled, a time lag is inevitable, and the measurement range cannot be switched instantaneously. As a result, a high-frequency signal cannot be measured. Also, the measurement accuracy between ranges varies depending on the magnitude of the input signal. For example,
In the “× 1” range of FIG. 9, [accuracy of 20V ÷ A / D conversion bit number], in the “× 10” range, [accuracy of 2V ÷ A / D conversion bit number], and in the “× 100” range, [0. 2V
The measurement accuracy differs for each range, such as the accuracy of [A / D conversion bit number]. As described above, when A / D conversion is used to digitize an analog signal, the measurement range is automatically switched according to the level of the analog signal, but the measurement accuracy is also switched at the same time. It is not possible to change the measurement range while maintaining

Accordingly, it is an object of the present invention to provide an analog signal measuring method and an analog signal measuring method which can expand the measuring range without switching the range even if the input signal is out of the measuring range of the A / D converter, and which does not change the measuring accuracy. It is to provide a measuring circuit.

[0007]

According to the present invention, there is provided a method for measuring an analog signal in which an analog input signal is digitized by an A / D converter for measurement. The input signal is A /
When exceeding the measurement range of the D converter, the input signal is level-converted so that the portion exceeding the measurement range falls within the measurement range, and the A / A signal is amplified without amplifying the level-converted signal. When input to a D converter and performing arithmetic processing using the digital output of the A / D converter, the level value of the input signal that is not included in the extraction is input to the A / D converter. And an analog signal measurement method characterized by performing processing so as to be added to a measurement result after A / D conversion by the A / D converter.

According to this method, when the input signal exceeds the measurement range of the A / D converter, the level is converted so that the portion beyond the measurement range of the input signal is measured, and this is converted as necessary. After amplification, it is input to the A / D converter as an input signal. By the level conversion of the input signal, even if the level of the input signal exceeds the measurement range of the A / D converter, the analog signal can be measured without switching the range. As a result, even if the value of the input signal falls outside the measurement range of the A / D converter, the measurement range can be expanded without performing range switching, and the measurement accuracy does not change.

According to a second aspect of the present invention, there is provided an analog signal measuring method for digitizing an analog input signal by an A / D converter for measurement. A predetermined measurement area is set at equal intervals for the maximum measurable value of the input signal exceeding the measurement range of, and one of the measurement areas is selected according to the level value of the input signal, and the A / D is selected. The present invention provides an analog signal measurement method, wherein when performing arithmetic processing using a digital output of a converter, an A / D conversion result by the A / D converter is corrected according to the selected measurement area.

According to this method, predetermined measurement regions are set at equal intervals with respect to the input signal, the whole is divided based on the measurement range, and any of the measurement regions is divided according to the level value of the input signal. Is selected, and the input signal input based on the selected measurement area is input to the A / D converter, so that even if the input signal exceeds the measurement range of the A / D converter, a Measurement of an analog signal can be performed without performing range switching. For a measurement in which a measurement area is set, a true measurement value can be obtained by performing correction according to the selected measurement area. Therefore, an input signal of an arbitrary level can be taken in without performing range switching, so that the measurement range is expanded. In addition, since range switching is not performed, there is no change in measurement accuracy.

In order to achieve the above object, the present invention has, as a third feature, an analog input signal for measuring an analog input signal.
In an analog signal measurement circuit for performing measurement by digitizing with a / D converter, a differential amplifier in which the input signal is input to one of two input terminals, and a level of an output signal of the differential amplifier being the A / D conversion A level comparison circuit that outputs data corresponding to the amount exceeding the measurement range of the device, a counter circuit that counts up or down according to output data of the level comparison circuit, and a counter circuit that counts up or down according to the count result of the counter circuit. An analog signal measuring circuit is provided, which comprises a D / A converter for applying an analog voltage to the other input terminal of the differential amplifier.

According to this configuration, when the input signal exceeds the measurement range of the A / D converter, data corresponding to the excess condition is generated by the level comparison circuit, and the data from the level comparison circuit is generated by the counter circuit. An analog signal corresponding to the count value is output from the D / A converter, input to the differential amplifier, and a difference from the input signal is obtained. This difference is converted into an input signal that falls within the measurement range of the A / D converter. Therefore, even if the input signal is out of the measurement range of the A / D converter, there is no need to switch the range, so that the measurement range can be expanded. In addition, since the range has not been switched,
There is no change in measurement accuracy.

In order to achieve the above object, the present invention has, as a fourth feature, an analog input signal for measuring an analog input signal.
In an analog signal measuring circuit that performs measurement by digitizing with an A / D converter, the analog signal is converted into digital data every time the input signal reaches the measurement range of the A / D converter.
/ D conversion means, D / A conversion means for converting the digital data by the A / D conversion means into an analog signal,
A differential amplifier that obtains a difference between the input signal and the analog signal output from the D / A conversion means, and amplifies the difference to a predetermined level or outputs the difference to the A / D converter without amplification. An analog signal measuring circuit is provided.

According to this configuration, when the input signal exceeds the measurement range of the A / D converter, digital data is generated by the A / D conversion means every time the excess reaches the measurement range,
This digital data is converted into an analog signal by the D / A converter. The difference between the analog signal and the input signal is obtained by a differential amplifier, and the difference is converted into an input signal that falls within the measurement range of the A / D converter.
Therefore, even if the input signal is out of the measurement range of the A / D converter, there is no need to switch the range, so that the measurement range can be expanded. In addition, since range switching is not performed, there is no change in measurement accuracy.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic configuration of an analog signal measuring circuit according to the present invention. The input signal Si is input to the measurement range excess determination unit 101 and the level conversion unit 102,
The level conversion unit 102 includes a measurement range excess determination unit 10
1 is input. Further, the level conversion unit 102
Is connected to an A / D converter 103. The specifications of the A / D converter 103 are, for example, a measurement range of ± 10 V and a conversion bit number of 8 bits.

FIG. 2 shows the operation of the analog signal measuring circuit of FIG. As shown in FIG. 2A, the A / D converter 10
Input signal Si of the waveform having a peak value exceeding the third measuring range V _R have been inputted. The input signal Si is made part of the level A, which will fit in the measurement range V _R, and the portion of the level B to enter the region of the measuring range V _R after exceeding the level A. For an input voltage A / D converter 103 exceeds the measurement range V _R, to be processed by that maximum value, the portion of the level B is not correctly A / D conversion process.

[0017] In the present invention, detecting that the portion exceeding the measuring range V _R to the input signal Si by measuring overrange determination section 101 (voltage V _B) is present, the determination signal SR _R to the level converter 102 Output. Level converter 10
2 receives the determination signal S _R and outputs a value (voltage V _B ) obtained by subtracting the voltage of V _R from the input signal Si as shown in FIG. To enter. The output of the A / D converter 103, since only digital value of the level B component, as in FIG. 2 (c), the final value by adding the digital values of V _R fraction had been subtracted.
In the above description, the method of subtracting the measurement range has been described. However, as described in the second embodiment,
A measurement area (= measurement range) is set at equal intervals with respect to an input signal that can be received as the input signal Si, and the input signal Si is set.
One of the measurement areas may be selected according to the level and input to the A / D converter 103. In this case, if the conversion result of the A / D converter 103 is corrected according to the selected measurement area, the true value of the input signal Si can be obtained.

[First Embodiment] FIG. 3 shows a first embodiment of the analog signal measuring circuit of the present invention. A level comparison circuit 2 and an amplifier 3 are connected to a differential amplifier 1 to which an analog signal Si to be measured is inputted to one input terminal, and an output signal is taken out from an output terminal of the amplifier 3. A counter circuit 4 is connected to the level comparison circuit 2, a D / A converter 5 is connected to the counter circuit 4, and an analog output of the D / A converter 5 is supplied to the differential amplifier 1.
Is input to the other input terminal. A clock generator 6 is connected to the level comparison circuit 2 and the D / A converter 5, and the level comparison circuit 2 and the D / A converter 5 are synchronized by a clock signal output from the clock generator 6.
Further, an arithmetic processing unit 7 for performing processing such as voltage measurement is connected to the counter circuit 4.
The output terminal of the amplifier 3 is connected to the converter 8. A
The / D converter 8 has, for example, a measurement range of ± 10 V and a conversion bit number of 8 bits. Therefore, the 1-bit resolution of the A / D converter 8 is 20 V / 2
55 = 0.078 V / bit.

FIG. 4 shows the operation of each part of the analog signal measuring circuit of FIG. Referring to FIG. 3 and FIG.
The operation of the embodiment will be described. As shown in FIG. 4A, the level of the analog signal Si changes and may exceed the currently set measurement range. This analog signal Si
Is input to one input terminal of the differential amplifier 1 and is amplified according to a set amplification factor. Further, in the differential amplifier 1, the analog signal Si falls within the measurement range.
A process of adding the output signal of the D / A converter 5 to the analog signal Si is performed.

The level comparison circuit 2 determines the level of the analog signal Si from the differential amplifier 1 based on the clock timing of the clock generator 6 to determine whether the measurement range is out of the + side or the-side, and sends it to the counter circuit 4. The data of the up count (when over on the + side) or the down count (when over on the minus side) is sent. For example, when the upper limit of the measurement range is exceeded (over the + side measurement range), FIG.
Is generated (up-count output).

The counter circuit 4 counts up or down based on the data of the level comparison circuit 2 and creates digital data to be added or subtracted from the input signal.
2B, the counter circuit 4 sets the count n (input addition data) to [n +
1]. Based on the output signal of the counter circuit 4, D
The / A converter 5 outputs one bit of D as shown in FIG.
An analog voltage obtained by adding the / A conversion output voltage (V ₅ ) is output. The one-bit voltage V ₅ is supplied to the clock generator 6.
Is sent to the differential amplifier 1 at the clock timing shown in FIG. Differential amplifier 1, by the subtraction of the voltage V _i of the input signal Si voltage V5 from the D / A converter 5, to the level change an analog signal Si in the measurement range. As a result, the output of the differential amplifier 1 becomes the analog signal Si as shown in FIG.
From the output voltage of the D / A converter 5 is obtained. The output signal of the differential amplifier 1 is sent to the amplifier 3 and, after a predetermined amplification, is input to the A / D converter 8. The output waveform of the amplifier 3 is the same as that shown in FIG. The arithmetic processing is performed by the arithmetic processing unit 7 using the digital output from the A / D converter 8, and at this time, using the input addition data 9 from the counter circuit 4, the continuous processing shown in FIG. Correction is performed so as to form a waveform.

As described above, according to the first embodiment,
Since an amplified output can be obtained without performing range switching for an input exceeding the measurement range of the analog signal Si, the measurement accuracy does not change unlike the conventional case. As a result, the measurement range can be expanded while maintaining the same measurement accuracy, and the measurement accuracy can be dramatically improved.

FIG. 5 shows the operation of the counter circuit 4. FIG.
When an input signal Si having a waveform as shown in FIG. 5A is inputted, and as shown in FIG. 5C, if the level exceeds the measurement range Vm, when the level increases, each clock from the clock generator 6 is output. The counter circuit 4 counts up. Then, when the input signal Si reaches a peak and the level starts to decrease, the counter circuit 4 counts down. In response to the count result of the counter circuit 4, the D / A converter 5 generates an output signal as shown in FIG.
The output voltage V 5 for one bit of the converter ₅ (the first time, the voltage at the count “0” in FIG.
Of the input signal Si, the voltage V _i
On the other hand, a voltage (V _i -V ₅ ) is output from the differential amplifier 1 as shown in FIG.

Next, a second embodiment of the present invention will be described. When the measurement range of the A / D converter 8 of the arithmetic processing unit 7 is ± 10 V, if the input signal Si is ± 0.01 V (that is, the width of the measurement range is 0.02 V), the front amplifier is used. A / D converter 8
To be measured. In such a configuration, as described in [0004], the input signal Si of ± 0.1 V cannot be measured due to input over unless the range is switched.

However, with some contrivance, −0.01
To +0.01 V, +0.01 to +0.03 V, +0.0
The width of the measurement range is set to 0.0 to 3 to +0.05 V.
2V, that is, the voltage width of the measurement range (= 0.02
The inventor has found that it can be solved by dividing into units of V). For example, in the case of an input signal Si of 0.01 to 0.03 V, subtract 0.02 V (0.01-0.03 V).
0.02) V- (0.03-0.02) V = -0.01
V to + 0.01V = convert to ± 0.01V measurement range,
In the case of an input signal Si of 0.03 to 0.05 V, 0.
By subtracting 04V and converting to a measurement range of ± 0.01V, the measurement range of the input signal can be expanded,
Even if the input signal Si exceeds 0.01 V, the measurement can be performed. It should be noted that the subtracted amount is the arithmetic processing unit 7
Need to be added. Therefore, the arithmetic processing unit 7 determines how much the subtracted data is as equally spaced measurement range data.
Notify. The arithmetic processing unit 7 corrects the measurement value after A / D conversion using the equally-spaced measurement range data. The second embodiment shows an analog signal measurement circuit provided with a circuit for realizing the above-described device. In the following, decomposing the input signal Si at equal intervals is referred to as “equally spaced measurement range”. The interval in this case is the final measurement range (the measurement range of the A / D converter 8).

Table 1 explains the voltage conversion processing for the input signal Si in the above three examples. For other input voltage ranges, the A / D
What is necessary is just to perform the process of subtracting the voltage so that the input voltage range of the converter 8 becomes ± 0.01 V. The same processing may be performed on the input signal Si having a voltage not shown here as long as the characteristics of the preamplifier 11 are guaranteed.

[Table 1]

FIG. 6 shows a second embodiment of the present invention. One input terminal of a differential amplifier 12 is connected to a preamplifier 11 for amplifying an input signal Si to a predetermined level.
The A / D converter 8 is connected to the differential amplifier 12. The output terminal of the preamplifier 11 further includes an A / D converter 8.
An A / D converter 13 is connected to the A / D converter 13. A D / A converter 14 is connected to the A / D converter 13, and an output terminal thereof is connected to the other input terminal of the differential amplifier 12. The A / D converter 13 is connected to a clock generator 15 that generates a clock signal for determining the sampling timing. The output signal of the A / D converter 13 is input to the arithmetic processing unit 7 as equally-spaced measurement range data 16. The A / D converter 13 has, for example, a measurement range of ± 10 V and a conversion bit number of 8 bits. Further, the amplification degree Av of the differential amplifier 12 is [A / D converter 8
Input range] / [1 bit amplitude of D / A conversion].

FIG. 7 shows operation waveforms of various parts of the analog signal measuring circuit of FIG. The operation of the second embodiment will be described with reference to FIGS. In the configuration of FIG. 6, the operation of the configuration of FIG. 4 in the case where the maximum measurement range of the input signal Si is ± 0.1 V and the final equidistant measurement range is the range of ± 0.01 V of the input signal Si will be described. . However, it is assumed that the measurement range of the A / D converter 13 is ± 10 V and the above-mentioned equally-spaced measurement range is ± 10 V. Preamplifier 1
1 amplifies ± 0.01 V (maximum value) of the input signal Si by 100 times by the preamplifier 11 and outputs a voltage of ± 10 V (maximum value) as shown in FIG. Preamplifier 11
Is input to the A / D converter 13, and when a ± 10V signal (corresponding to ± 0.1V of the input signal Si) is divided into n equal parts (in the range of 0.02V described in [0025]), The output is converted so as to correspond to 2 V, so that n = 10, that is, A / D converted at 2 V intervals ((b) in FIG. 7). The D / A converter 14 converts the A / D converted data by the A / D converter 13 into an analog value as shown in FIG. 5C (−10, −8 V, −6 V,... +6).
V, + 8V, + 10V, etc.). This analog conversion value is output to the differential amplifier 12. The differential amplifier 12 outputs the output voltage of the preamplifier 11 (a voltage value obtained by multiplying the input signal Si by 100).
The difference between the output voltage of the D / A converter 14 and the output voltage of the D / A converter 14 is shown in FIG.
And amplify it 10-fold. In this state, the arithmetic processing unit 7 cannot know what kind of processing has been performed before the differential amplifier 12,
Processing is performed as if it were input in the range of 1V. Therefore, the output of the A / D converter 13 is notified to the arithmetic processing unit 7 as the equally-spaced measurement range data 16. As described above, in the second embodiment, the input signal S exceeding the measurement range is used.
It is characterized in that the difference processing for i is performed feedforward to the differential amplifier. Meanwhile, the first
In the embodiment, it can be said that the difference processing for the excess of the measurement range is performed on the differential amplifier 1 in a feedback manner.

Further, a specific value will be described. For example, assume that the input signal Si is in the range of +0.05 to + 0.07V. In this case, the output voltage of the preamplifier 11 becomes +5 to + 7V which is 100 times. This output voltage is A / D
When converted by the converter 13, the conversion is performed at intervals of 2V.
For an input voltage of +5 to 7 V, an A / D conversion value of 6
V is output and input to the other input terminal of the differential amplifier 12. In the differential amplifier 12, the output 6V of the D / A converter 4 is subtracted from the output voltage (5-7V) of the preamplifier 11, and (5-6) V- (7-6) V = -1 to + 1V = ± 1
V, and ± 1 V is amplified ten times to output a voltage of ± 10 V.

Assuming that the A / D converter 13 and the D / A converter 14 are not provided, the differential amplifier 12 outputs +5 to +7 V with respect to the input signal Si of +0.05 to +0.07 V.
Is output and amplified by the A / D converter 13 to be +50 to +
70 V, which exceeds the measurement range of ± 10 V, so that measurement is impossible. However, according to the present invention, the measurement range (± 1
0 V) is converted to ± 1 V by the A / D converter 13 and a value (± 10 V) multiplied by 10 is output from the A / D converter 13. The measurement range does not exceed in the system of the above.

[0031]

As is clear from the above, according to the analog signal measuring method of the present invention, when the input signal exceeds the measuring range of the A / D converter, the portion beyond the measuring range becomes a measuring object. Is converted as shown in FIG.
Since the input signal is input to the converter, the measurement range can be expanded without switching the range even if the input signal is out of the measurement range of the A / D converter. Moreover,
Since range switching is not performed, measurement accuracy can be dramatically improved without changing measurement accuracy.

According to another analog signal measuring method of the present invention, predetermined measurement areas are set at equal intervals with respect to an input signal, and the entire area is divided based on a measurement range to obtain a level of the input signal. By selecting one of the measurement areas according to the value and inputting the input signal based on the selected measurement area to the A / D converter, the input signal is measured in the measurement range of the A / D converter. The analog signal can be measured without switching the range as in the past, so that any level of input signal can be captured without switching the range, thus expanding the measurement range. You. In addition, since range switching is not performed, there is no change in measurement accuracy, and measurement accuracy can be dramatically improved.

According to the analog signal measuring circuit of the present invention,
A level comparison circuit generates data corresponding to a situation where the input signal exceeds the measurement range of the A / D converter, counts the data by a counter circuit, and converts an analog signal corresponding to the count value into a D / A converter. , And this is input to a differential amplifier, and the difference between the inputs is taken.
Since the D-conversion is performed, even if the input signal is out of the measurement range of the A / D converter, the measurement range can be expanded without performing range switching. In addition, since range switching is not performed, measurement accuracy does not change, and measurement accuracy can be dramatically improved.

Further, according to another analog signal measuring circuit of the present invention, when the input signal exceeds the measurement range of the A / D converter, the digital signal is converted by the A / D conversion means every time the excess reaches the measurement range. Data is generated, the digital data is converted into an analog signal by D / A conversion means, the difference between the analog signal and the input signal is obtained by a differential amplifier, and the difference is measured by an A / D converter. Therefore, even if the input signal is out of the measurement range of the A / D converter, the measurement range can be expanded without switching the range. In addition, since the range has not been switched,
The measurement accuracy does not change, and the measurement accuracy can be dramatically improved.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart showing an operation of the analog signal measurement circuit of FIG.

FIG. 3 is a block diagram showing a first embodiment of the analog signal measuring circuit according to the present invention.

4 is a waveform chart showing the operation of each part of the circuit of FIG.

FIG. 5 is a waveform chart showing an operation of the counter circuit 4.

FIG. 6 is a block diagram showing a second embodiment of the present invention.

FIG. 7 is a waveform diagram showing operation waveforms of respective parts of the analog signal measurement circuit of FIG.

FIG. 8 is a block diagram showing a conventional analog signal measurement circuit using an A / D converter.

FIG. 9 is an explanatory diagram showing the concept of automatic measurement range switching in FIG.

[Explanation of symbols]

 Reference Signs List 1,12 Differential amplifier 2 Level comparison circuit 3 Amplifier 4 Counter circuit 5,14,103 D / A converter 6,15 Clock generator 11 Preamplifier 13 A / D converter 101 Measurement range excess determination unit 102 Level conversion unit

Claims (7)

[Claims] 1. An analog signal measuring method for digitizing an analog input signal by an A / D converter for measurement, wherein when the input signal exceeds a measurement range of the A / D converter, the input signal exceeds the measurement range. Level-converting the input signal so that the input signal falls within the measurement range, amplifying the level-converted signal, or inputting the signal without amplification to the A / D converter; When performing arithmetic processing using an output, a level value of the input signal which is not included in the extraction among the input signals is added to a measurement result after A / D conversion by the A / D converter. An analog signal measuring method characterized by processing. 2. The analog signal measuring method according to claim 1, wherein the level conversion is performed by subtracting one or more analog values in the measurement range from the input signal. 3. An analog signal measuring method for performing measurement by digitizing an analog input signal by an A / D converter, wherein a maximum measurable value of the input signal exceeding a measurement range of the A / D converter is determined. Predetermined measurement areas are set at equal intervals, any one of the measurement areas is selected according to the level value of the input signal, and the arithmetic processing is performed using the digital output of the A / D converter. An analog signal measuring method, comprising: correcting an A / D conversion result by the A / D converter according to a measurement area. 4. The analog signal measuring method according to claim 3, wherein said predetermined measurement area is equal to said measurement range of said A / D converter. 5. An analog input signal for measuring A /
An analog signal measurement circuit which performs measurement by digitizing with a D converter, wherein: a differential amplifier to which the input signal is input to one of two input terminals; A level comparison circuit that outputs data corresponding to the amount of data exceeding the measurement range of the above, a counter circuit that counts up or down according to output data of the level comparison circuit, and an analog that corresponds to a count result of the counter circuit. An analog signal measuring circuit, comprising: a D / A converter for applying a voltage to the other input terminal of the differential amplifier. 6. An analog input signal for measuring an analog input signal
An analog signal measurement circuit that performs digitization and measurement by a D converter, wherein the A / D converter converts the input signal into digital data each time the input signal reaches a measurement range of the A / D converter; D / A conversion means for converting the digital data into an analog signal by the conversion means, and calculating a difference between the input signal and the analog signal output from the D / A conversion means, and amplifying the difference to a predetermined level. An analog signal measuring circuit comprising a differential amplifier that outputs the signal to the A / D converter without amplifying the signal. 7. The analog signal measuring circuit according to claim 4, wherein a preamplifier for amplifying the input signal to a predetermined level is connected to the preceding stage of the A / D converter.