JP2000162251A - Apparatus and method for measuring voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide with a simpler circuit configuration an apparatus and a method for measuring a voltage, wherein a conversion resolving power for the voltage to be measured can be varied without increasing measurement errors. SOLUTION: One voltage is selected by a selector from among a plurality of reference voltage and set as a conversion reference voltage Vr of an A/D converter 1. A known fixed voltage Vf within a predetermined error range is supplied to one input terminal Ain3 for a voltage to be measured from a voltage feed circuit 2. The conversion reference voltage Vr is corrected at a CPU 5 on the basis of the conversion result of the fixed voltage Vf by the A/D converter 1, whereby a corrected conversion reference voltage is obtained. Voltage to be measured and supplied to the other input terminals (Ain1, Ain2) are obtained, on the basis of conversion results of the voltages to be measured by the A/D converter 1 and the corrected conversion reference voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage measuring device and a voltage measuring method, and more particularly to a voltage measuring device and a voltage measuring method capable of keeping a voltage error within a certain range for each conversion reference voltage with a simpler circuit configuration. The present invention relates to a voltage measuring apparatus and a voltage measuring method which have a simple circuit configuration and can change the conversion resolution of a voltage to be measured without increasing a measurement error.

[0002]

2. Description of the Related Art Conventionally, as a measurement system for measuring a change in voltage, for example, an analog / digital converter (hereinafter referred to as A / D converter) has been used.
/ D converter). The A / D converter includes a plurality of input terminals for measurement and an input terminal for one conversion reference voltage. The A / D converter converts the plurality of input voltages for measurement and outputs “input terminal voltage / It is output as a digital value corresponding to the “conversion reference voltage”. Here, even if a voltage to be measured equal to or more than the value of the conversion reference voltage is input to the input terminal of the measurement target, it cannot be converted by the A / D converter. ) Cannot be set below the maximum value.

In a conventional voltage measuring device, A
The digital output of the / D converter is input to a CPU such as a microprocessor, and the actual voltage to be measured is calculated. That is, in order to calculate the actual measurement target voltage, it is necessary to treat the conversion reference voltage as a known value, and the calculation program of the CPU incorporates the theoretical value of the conversion reference voltage in advance as a fixed value. I have. Therefore, in order to install the same calculation program in a plurality of the same voltage measuring devices, it is necessary to keep the conversion reference voltage of each voltage measuring device within a certain error range, and circuit measures have been taken for that purpose. . Further, since the conversion resolution of the A / D converter itself is also finite, the minimum change value of the measured voltage that can be determined by the voltage measuring device is “conversion reference voltage / resolution of A / D converter”.

On the other hand, since the set value of the conversion reference voltage is determined by the maximum input voltage value to be measured as described above, as a result, the minimum voltage change value that can be determined by the voltage measuring device is “the maximum value to be measured”. The input voltage value / resolution of the A / D converter is limited, and has no relation to the voltage fluctuation range of each input terminal. For this reason, when the voltage fluctuation ranges of the input terminals differ greatly, there is a disadvantage that the measurement resolution differs for each input terminal. Explaining with specific numerical values, there are two input targets, and the respective voltage change ranges are 0 to 12 V and 0 to 3
V and the resolution of the A / D converter is 8 bits, one input target 0 to 12 V can be measured with a maximum 8-bit resolution, while the other input target 0 to 3 V
Can measure only with a quarter of the resolution of 6 bits.

[0005]

As described above, the above-described conventional voltage measuring apparatus has a problem that the measurement resolution differs for each input terminal when the voltage fluctuation range of each input terminal greatly differs. This problem can be solved by preparing a plurality of conversion reference voltage circuits optimized for each input target, sequentially switching the circuit for each measurement of each input target, and inputting the same to the conversion reference voltage input terminal of the A / D converter. ,in this case,
In order to install the same calculation program on a plurality of identical voltage measuring devices, it is necessary to keep the conversion reference voltage of each voltage measuring device within a certain error range, and if measures are taken for that, the circuit scale will increase. There were circumstances.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems and circumstances, and has a simpler circuit configuration, and a voltage error of each conversion reference voltage is kept within a certain range for a high-precision voltage. An object of the present invention is to provide a voltage measuring device and a voltage measuring method capable of performing a measurement. Another object of the present invention is to
With a simpler circuit configuration and without increasing the measurement error,
An object of the present invention is to provide a voltage measuring device and a voltage measuring method capable of changing a conversion resolution of a voltage to be measured.

[0007]

According to the present invention, the actual voltage value supplied to the input terminal of the conversion reference voltage of the analog / digital converter is supplied to one of the input terminals of the voltage to be measured. After confirming based on a known fixed voltage value within a predetermined error range and an analog / digital conversion result of the fixed voltage, an unknown measurement target voltage supplied to another input terminal is obtained from the analog / digital conversion result. Thus, the voltage error is kept within a certain range for each conversion reference voltage.

That is, the voltage measuring device according to the present invention comprises:
"In a voltage measuring apparatus provided with an analog / digital converter having a plurality of input terminals for a voltage to be measured and one input terminal for a conversion reference voltage, one of the input terminals for the voltage to be measured may be within a predetermined error range. A voltage supply means for supplying a known fixed voltage, and a conversion reference voltage after correction by correcting the conversion reference voltage based on a conversion result of the fixed voltage by the analog / digital converter. Control means for determining a measurement target voltage supplied to the other input terminal based on a conversion result of the measurement target voltage supplied to the other input terminal by the device and the corrected conversion reference voltage. Characteristic voltage measurement device. "
(Claim 1) is a gist (items specifying the invention):-Selects one of a plurality of reference voltages based on a selection instruction of the control means and inputs the selected reference voltage to an input terminal of a conversion reference voltage of the analog / digital converter. It has a selecting means for supplying (claim 2).

Further, the voltage measuring method according to the present invention provides a method for measuring a voltage of a voltage measuring apparatus provided with an analog / digital converter having a plurality of input terminals for measuring voltages and an input terminal for one conversion reference voltage. A voltage supply step of supplying a known fixed voltage within a predetermined error range to one of input terminals of the voltage to be measured, and the conversion reference voltage based on a result of conversion of the fixed voltage by the analog / digital converter. And a correction step of correcting the conversion reference voltage to obtain a corrected conversion reference voltage, based on a conversion result of the measurement target voltage supplied to another input terminal by the analog / digital converter and the conversion reference voltage after the correction. And a measuring step for obtaining a voltage to be measured supplied to the other input terminal. "(Claim 3) And term), that by selecting one of the plurality of reference voltages based on-selection instruction having a selection step of supplying to the input terminal of the conversion reference voltage of the analog / digital converter (claim 4),
It is characterized by the following.

In the voltage measuring device and the voltage measuring method according to the present invention, one of the input terminals of the voltage to be measured is supplied from the voltage supply means.
Finally, a known fixed voltage with a lower error within a predetermined error range is supplied (voltage supply step).
Based on the result of the conversion of the fixed voltage by the digital converter, the conversion reference voltage for which a strict error regulation is not required is corrected to obtain a corrected conversion reference voltage (correction step). Based on the conversion result of the measurement target voltage supplied to the input terminal and the corrected conversion reference voltage, the measurement target voltage supplied to the other input terminal is determined (measurement step). Item 3). This makes it possible to keep the voltage error within a certain range for each conversion reference voltage with a simpler circuit configuration in which a voltage supply means is added to the conventional device configuration.

Further, in the voltage measuring apparatus and the voltage measuring method according to the present invention, the selecting means (selecting step) selects one of the plurality of reference voltages based on the selection instruction of the control means, and performs the analog / digital conversion. Is supplied to the input terminal of the conversion reference voltage (claims 2 and 4). In other words, even when a plurality of conversion reference voltages of the analog / digital converter are selected in order to make the measurement resolution appropriate, it can be realized with a simpler circuit configuration of adding a voltage supply means to the conventional device configuration, As a result, the conversion resolution of the voltage to be measured can be made variable with a simpler circuit configuration and without increasing the measurement error.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail. As described above, the present invention is applied to an input terminal of a conversion reference voltage of an analog / digital converter (hereinafter, referred to as an A / D converter). After confirming the actual voltage value based on a known fixed voltage value within a predetermined error range supplied to one of the input terminals of the voltage to be measured and the A / D conversion result of the fixed voltage, The unknown voltage to be measured supplied to the input terminal is obtained from the A / D conversion result. Next, examples of the voltage measuring device and the voltage measuring method according to the present invention will be described, and the present invention will be specifically described. However, the present invention is not limited to only the following examples, and is described above. Various modifications and changes are possible within the scope of the voltage measuring device and the voltage measuring method according to the present invention.

FIG. 1 is a diagram showing a configuration of a voltage measuring device according to one embodiment of the present invention. As shown in FIG. 1, the voltage measurement device of the present embodiment includes an A / D converter 1, a voltage supply circuit 2, a DC / DC converter 3, a selector 4, and a CPU 5.

First, each component of the voltage measuring device shown in FIG. 1 will be described. The A / D converter 1 corresponds to an analog / digital converter referred to in the claims, and has three input terminals Ain1 to Ain3 of a voltage to be measured and one input terminal Vref of a conversion reference voltage, and each input Ai.
A / D conversion results of n1 to Ain3 are converted into digital data DA corresponding to “input terminal voltage to be measured / conversion reference voltage”.
Output as T. In this embodiment, the output voltage V of the voltage supply circuit 2 is connected to the input terminal Ain3 of the voltage to be measured.
f is the selector 4 at the input terminal Vref of the conversion reference voltage.
Are supplied, and the unknown measurement target voltages Vin1 and Vin2 to be measured are supplied to the input terminals Ain1 and Ain2, respectively, and are measured.

The voltage supply circuit 2 corresponds to voltage supply means.
A known fixed voltage within a predetermined error range is supplied to one input terminal Ain3 of the voltage to be measured. In FIG. 1, a configuration including a resistor R and a constant voltage diode ZD, which is stable in temperature and is the most common configuration as a constant voltage source, is used. Since the internal resistance of the constant voltage diode ZD is sufficiently smaller than the resistance R, a voltage substantially equal to the Zener breakdown voltage Vz of the constant voltage diode ZD is obtained as the output voltage Vf. Diode Z
A stable output of a fixed voltage determined by the characteristic of D is possible. The input voltage of the voltage supply circuit 2 includes DC / D
The voltage Vcc which is one of the outputs of the C converter 3 is used.

The DC / DC converter 3 includes Vcc, Vd
The three reference voltages d and Vee are generated and supplied to the selector 4. In addition, each reference voltage Vcc, Vdd, Vee
Is not subject to strict error rules,
The configuration of the DC / DC converter 3 can be a simple configuration. Further, the selector 4 corresponds to a selection unit,
An input terminal of a conversion reference voltage of the A / D converter 1 by selecting one of three types of reference voltages Vcc, Vdd, and Vee generated by the DC / DC converter 3 based on a control signal CON for performing a selection instruction from the CPU 5. Vref.

Further, the CPU 5 corresponds to a control means and is realized by a microprocessor or the like. In CPU 5, A / D
The conversion reference voltage Vr is corrected based on the conversion result of the fixed voltage Vf by the converter 1, and the corrected conversion reference voltage Vr ′ is corrected.
And another input terminal Ain by the A / D converter 1
1, Ain2, the voltage to be measured Vin1, Vi supplied to Ain2
Based on the conversion result of n2 and the corrected conversion reference voltage Vr ', a voltage to be measured supplied to the other input terminal is obtained.

Next, a voltage measuring method in the voltage measuring apparatus according to the present embodiment will be described with reference to the flowchart of FIG. Note that the flowchart of FIG. 2 illustrates the processing of a program executed by the CPU 5 of the voltage measurement device according to the present embodiment. First, in the program, approximate value information of each reference voltage Vcc, Vdd, Vee of the DC / DC converter 3 which is an input candidate for the input terminal Vref of the conversion reference voltage Vr of the A / D converter 1 is incorporated in advance. .

In step S201, the DC / DC is selected by the selector 4 based on the selection instruction by the control signal CON.
One of the reference voltages Vcc, Vdd and Vee from the converter 3 is selected and supplied to the input terminal Vref of the A / D converter 1 as a conversion reference voltage Vr. Step S202
Then, the A / D conversion target in the A / D converter 1 is set to the input terminal Ain3, that is, the fixed voltage Vf which is the output of the voltage supply circuit 2, by the selection signal SEL.
A / D conversion result corresponding to “/ conversion reference voltage Vr” is obtained via digital data DAT. Next, the fixed voltage V
From the conversion result of f and the value of the fixed voltage Vf given in advance, an accurate voltage value (V) for the reference voltage Vcc, Vdd or Vee selected as the conversion reference voltage Vr.
r ′) to obtain and correct. Steps S201 and S2 above
The process 02 is repeated by the number of reference voltages (three in this embodiment) output from the DC / DC converter 3 to the selector 4, and correction values for the respective reference voltages Vcc, Vdd, and Vee are stored.

Next, in step S204, the input terminal Ain1 or Ain2 to be measured is selected by the selection signal SEL. In step S205, one of the reference voltages Vcc, Vdd, and Vee is reselected by the selector 4 according to the selection instruction by the control signal CON.
It is supplied to the input terminal Vref of the A / D converter 1 as the conversion reference voltage Vr. Here, the DC / DC converter 3
Since the reference voltages Vcc, Vdd, and Vee are usually set to different values according to the voltage change range of the measurement target in order to optimize the conversion resolution, the reference voltages Vcc, Vdd
The reselection of dd and Vee is determined by a rough measurement result of the measurement target voltage performed in advance, or when the voltage change range is determined for each input terminal of the measurement target, the selected input terminal is selected. What is necessary is just to determine according to it. Further, in step S206, the A / D converter 1 of the voltage to be measured supplied to the selected input terminal
Based on the A / D conversion result (digital data DAT) and the correction value Vr ′ of the conversion reference voltage Vr (the currently reselected reference voltage) calculated and stored in step S202. to decide.

Next, the effectiveness of the voltage measuring device and the voltage measuring method of the present embodiment will be considered in comparison with a conventional voltage measuring device. The A / D conversion result in the A / D converter 1 is based on the input terminal V of the conversion reference voltage of the A / D converter 1.
The relative ratio of the input terminal voltage of each measurement target to the voltage supplied to ref is represented by “input terminal voltage of the measurement target / conversion reference voltage”. In the conventional voltage measurement device, the input voltage to the conversion reference voltage input terminal The value is incorporated into the measurement program of the CPU as a fixed fixed value, and this fixed value and A /
The voltage input value of each input terminal to be measured is calculated based on the D conversion result. However, actually, an error occurs between the measurement result obtained by the A / D conversion and the actual voltage to be measured, and the error is large in the resolution of the A / D converter itself and the stability of the conversion reference voltage. Dependent. Therefore, in the conventional voltage measuring apparatus, attention has been focused on how to stabilize the conversion reference voltage value in the actual circuit configuration with a small error with respect to the fixed value of the conversion reference voltage incorporated in the measurement program. Here, in order to provide high stability, it is necessary to first set the conversion reference voltage of the A / D converter to a certain target voltage. The target value depends on where to set the measured voltage rise of the input to be measured. It is determined. This is A /
This is because the D converter cannot convert properly unless the voltage to be measured is equal to or lower than the voltage set at the input terminal of the conversion reference voltage. Suppose that the resolution of the A / D converter is 8 bits and the same A / D converter inputs and measures a measurement target voltage that varies in the range of 0 to 12 V and a measurement target voltage that varies in the range of 0 to 3 V. In the conventional voltage measuring device, the minimum fluctuation amount of the input voltage that can be determined by the A / D converter is fixed to "(12V-0V) / 8 bits". On the other hand, it was possible to measure only with a resolution of substantially 6 bits. In addition, in order to measure a voltage to be measured of 0 to 3 V with the same 8-bit resolution using a conventional voltage measuring device, a conversion reference voltage circuit corresponding to the voltage to be measured of 0 to 3 V is additionally provided. This can be achieved by selecting and supplying the signal to the A / D converter as necessary. However, in order to reduce the measurement error, the additional conversion reference voltage circuit needs to have high stability as described above. is there.

With respect to such a conventional voltage measuring device,
In the voltage measuring device and the voltage measuring method according to the present embodiment,
A known fixed voltage value (Vf) having a high stability necessary for calculating the measurement target voltage is uniquely supplied from the voltage supply circuit 2 to one of the input terminals (Ain3) of the A / D converter 1 to be measured. Only based on the fixed voltage Vf, the conversion reference voltage Vr actually input to the A / D converter 1
Can be calculated and corrected, the conversion reference voltage of the A / D converter 1 can be selected from a plurality of reference voltages in order to optimize the resolution. As a result, the voltage error can be kept within a certain range for each conversion reference voltage with a simpler circuit configuration, and the measurement error can be increased with a simpler circuit configuration. In addition, the conversion resolution of the voltage to be measured can be made variable.

In the configuration of the voltage measuring apparatus according to the present embodiment shown in FIG. 1, the constant voltage diode ZD is used to generate the stabilized low error fixed voltage Vf supplied to the A / D converter 1. Although the operation is performed by the voltage supply circuit 2, the voltage supply circuit 2 may be configured by other constant voltage output circuit means such as a regulator. A / D
The reference voltages Vcc, Vdd, Vee, which are candidates for the conversion reference voltage to be supplied to the input terminal Vref of the converter 1, are
Although it is configured to be generated by the C / DC converter 3, it can be replaced by another DC voltage such as a battery or an AC adapter output.

[0024]

As described above in detail, according to the voltage measuring apparatus and the voltage measuring method of the present invention, a known method having a lower error within a predetermined error range from the voltage supply means to one of the input terminals of the voltage to be measured. A fixed voltage is supplied (voltage supply step), and the control means corrects the conversion reference voltage for which a strict error is not stipulated based on the conversion result of the fixed voltage by the analog / digital converter, and converts the corrected conversion reference voltage. (Correction step), based on the result of conversion of the voltage to be measured supplied to another input terminal by the analog / digital converter and the converted reference voltage after correction, the voltage to be measured supplied to the other input terminal (Measurement step), the voltage error is kept within a certain range for each conversion reference voltage with a simpler circuit configuration in which voltage supply means is added to the conventional device configuration. It can be, it is possible to voltage measurement precision (claim 1, claim 3).

According to the voltage measuring apparatus and the voltage measuring method of the present invention, one of the plurality of reference voltages is selected by the selecting means (selecting step) based on the selection instruction of the control means, and the analog / digital conversion is performed. Voltage is supplied to the input terminal of the conversion reference voltage of the converter, so even if multiple conversion reference voltages of the analog / digital converter are selected to optimize the measurement resolution, the voltage is supplied to the conventional device configuration. The conversion resolution of the voltage to be measured can be changed with a simpler circuit configuration and without increasing the measurement error as a result. Item 4).

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a voltage measuring device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a voltage measuring method in the voltage measuring device according to the embodiment.

[Explanation of symbols]

 Reference Signs List 1 A / D converter (analog / digital converter) 2 Voltage supply circuit (voltage supply means) 3 DC / DC converter 4 Selector (selection means) 5 CPU (control means) R Resistance ZD Constant voltage diode Vcc, Vdd, Vee reference Voltage Vr Conversion reference voltage Vin1, Vin2 Measurement target voltage Vf Fixed voltage Vref Conversion reference voltage input terminal Ain1 to Ain3 Measurement target voltage input terminal CON control signal DAT digital data SEL selection signal

Claims (4)

[Claims] 1. A voltage measuring apparatus comprising an analog / digital converter having a plurality of input terminals for a voltage to be measured and one input terminal for a conversion reference voltage, wherein one of the input terminals for the voltage to be measured is: Voltage supply means for supplying a known fixed voltage within a predetermined error range; and correcting the conversion reference voltage based on a conversion result of the fixed voltage by the analog / digital converter to obtain a corrected conversion reference voltage. Control means for obtaining a voltage to be measured to be supplied to the other input terminal based on a conversion result of the voltage to be measured supplied to another input terminal by the analog / digital converter and the corrected reference voltage; A voltage measuring device comprising: 2. The apparatus according to claim 1, further comprising a selection unit that selects one of a plurality of reference voltages based on a selection instruction from the control unit and supplies the selected reference voltage to an input terminal of a conversion reference voltage of the analog / digital converter. Item 2. The voltage measuring device according to Item 1. 3. A voltage measuring method for a voltage measuring apparatus provided with an analog / digital converter having a plurality of input terminals for a voltage to be measured and one input terminal for a conversion reference voltage, wherein: One is a voltage supply step of supplying a known fixed voltage within a predetermined error range, and the conversion reference voltage is corrected by correcting the conversion reference voltage based on a conversion result of the fixed voltage by the analog / digital converter. And a measurement supplied to the other input terminal based on a conversion result of the voltage to be measured supplied to another input terminal by the analog / digital converter and the converted reference voltage after the correction. A measuring step of obtaining a target voltage. 4. A method in which a plurality of reference voltages are set to one based on a selection instruction.
4. The voltage measuring method according to claim 3, further comprising a selecting step of selecting one of them and supplying the selected one to an input terminal of a conversion reference voltage of the analog / digital converter.