JPH01123161A - Zero offset correction apparatus of voltage measuring device - Google Patents

Abstract

PURPOSE:To accurately measure voltage, by a method wherein a zero offset means reads the zero offset value stored in a memory means to perform addition and subtraction. CONSTITUTION:When a zero offset correction time is set, a relay contact SW1 is closed while a relay contact SW2 is opened and the input of a voltage measuring part 1 is shortcircuited and potential difference becomes 0V. Therefore, the measuring part 1 can input accurate 0V voltage. Next, when the measuring part 1 measures the inputted 0V voltage, the measuring signal corresponding to 0V is outputted and stored in an internal RAM by a microcomputer 3 to release the zero offset correction time. At the time of measurement, the contact SW1 is opened and the contact SW2 is closed. When a voltage measuring terminal is connected to an object to be measured in this state, the voltage of the object to be measured is inputted to the measuring part 1. The input voltage is converted in the measuring part 1 by an A/D converter and the measuring signal corresponding to the voltage value is outputted. In the microcomputer 3, the zero offset value stored in the RAM is read to be added to or subtracted from the measuring signal and the voltage value corresponding to the measuring signal is displayed on a display part 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a zero offset correction device for correcting a zero offset potential in a voltage measuring instrument that measures voltage.

[Conventional technology]

A conventional voltage measuring device is comprised of a voltage measuring section 11 and a display section 12, as shown in FIG.

The voltage measurement section 11 has a voltage measurement terminal connected to its input side. The voltage applied between the voltage measurement terminals is input to the voltage measurement section 11, converted into a measurement signal, and output. In the case of a digital voltmeter, the measurement signal is a digital signal obtained by A/D converting the input voltage, and in the case of an analog voltmeter, it is an analog signal obtained by appropriately dividing the input voltage.

This measurement signal is input to the display section 12, and the corresponding value is displayed. In the case of a digital voltmeter, the display section 12 is a device that typically displays numerical values using a seven-segment LCD array, and in the case of an analog voltmeter, it is a device that typically displays numerical values using a pointer meter. The value displayed on this display section 12 becomes the measured voltage value.

[Problem that the invention seeks to solve]

However, when attempting to perform accurate measurements using a conventional voltage measuring instrument configured in this manner, it is necessary to adjust the zero offset potential of the voltage measuring section 11 with high precision, and to compensate for temperature drift. It also becomes necessary to provide a circuit. Therefore, conventional voltage measuring instruments have the problem of requiring highly accurate adjustment and temperature compensation circuits to perform accurate measurements.

[Means for solving problems]

The zero offset correction device for a voltage measuring instrument according to the present invention includes:
In order to solve the above problems, in voltage measuring instruments that convert the input voltage into a measurement signal in the voltage measuring section and display it on the display section, we have developed a short-circuit switch that can short-circuit the input of the voltage measuring section, and a When the short-circuit switch is short-circuited by the short-circuit switch, when the input voltage of the voltage measurement section is measured at this time, the input voltage of the voltage measurement section or the measurement signal is added or subtracted. A zero offset value output means that outputs a zero offset value that can make the signal a value corresponding to OV, a storage means that stores the zero offset value outputted by the zero offset value output means, and a short-circuit switch/reset at the time of measurement. When the input voltage of the voltage measuring section is measured when the short-circuit switch is opened by the opening means for opening the circuit and the short circuit switch is opened by the opening means, the zero offset value stored in the storage means is read out and the voltage measurement at this time is performed. The present invention is characterized in that it has a zero offset means for performing zero offset by adding or subtracting the input voltage or measurement signal of the section.

[For production]

The start of zero offset correction depends on the operator's operation. Further, when the operator performs a measurement start operation, zero offset correction can be automatically performed before measurement.

At the time of zero offset correction, the shorting means first shorts the shorting switch. Then, the input of the voltage measuring section is short-circuited and the potential difference becomes OV (volt).

Therefore, when the input voltage of the voltage measurement section is measured at this time, the zero offset value output means outputs a zero offset value so that OV is displayed on the display section. This zero offset value becomes a value corresponding to the object to which the zero offset means adds or subtracts it later. Therefore, when the zero offset means adds or subtracts to the measurement signal that is the output of the voltage measurement section, the difference between the measurement signal corresponding to Ov and the measurement signal output from the voltage measurement section during zero offset correction is the zero offset. value. Further, when the zero offset means adds or subtracts to the input voltage of the voltage measuring section, the input voltage for the voltage measuring section to output a measurement signal corresponding to 0V becomes this zero offset value.

The zero offset value output from the zero offset value output means is stored by the storage means.

During the measurement, the opening means opens the shorting switch. Normally, this shorting switch is always open. Thereby, the voltage to be measured can be input to the voltage measuring section. This voltage is converted into a measurement signal by the voltage measuring section and displayed on the display section. At this time, the zero offset means reads out the zero offset value stored in the storage means and performs addition and subtraction. Therefore, the measured value displayed on the display is an accurate value with zero offset.

[Example 1] An example of the present invention will be described below based on FIG.

This embodiment shows a case where zero offset is performed using a microcomputer.

As shown in FIG. 1, the voltage measuring device of this embodiment is composed of a voltage measuring section 1, a display section 2, a microcomputer 3, and relay contacts SW, SWz.

A relay contact SW is provided on the input side of the voltage measuring section 1.

- A pair of voltage measurement terminals are connected via SW2. Relay contact SW1 is a normally closed contact connected in parallel to a pair of voltage measurement terminals, and can short-circuit the input of voltage measurement section 1. Relay contact SW2 is a normally closed contact connected in series between one voltage measurement terminal and the input of voltage measurement section 1 connected to this, and can cut off input from this voltage measurement terminal. It looks like this.

Note that the relay contact SW1 corresponds to the short circuit switch in the zero offset correction device.

The voltage measurement unit 1 is composed of an A/D converter, and converts an input voltage, which is an analog signal, into a digital signal.
This is a circuit that outputs a measurement signal.

The output of the voltage measuring section 1 is connected to the input of the microcomputer 3. -1 Based on the measurement signal output from the voltage measuring section 1, a zero offset value is calculated and stored during zero offset correction, and zero offset is performed during measurement.

The display unit 2 is connected to the microcomputer 3 . The display unit 2 is composed of a display device consisting of a seven-segment LCD array and its driver. The microcomputer 3 then inputs the zero-offset measurement signal and displays the corresponding voltage value.

The operation of the voltage measuring instrument having the above configuration will be explained.

When the setting for zero offset correction is made by an operator's operation, first, relay contact SW is closed, and relay contact SW2 is opened. When the relay contact SWl closes, the input of the voltage measuring section 1 is short-circuited and the potential difference becomes OV. Therefore,
The voltage measurement unit 1 can input accurate Ov lightning voltage. When the relay contact SWz opens, the connection between the voltage measurement terminal and the input of the voltage measurement section 1 is cut off. Thereby, even when the voltage measurement terminal is connected to the object to be measured, it is possible to close the relay contact SWl and perform zero offset correction, making it convenient for use.

Next, the voltage measurement unit 1 measures the input Ov lightning voltage.

Normally, when the voltage measuring section 1 measures the OV lightning voltage, the OV
A measurement signal corresponding to this will be output. However, if the adjustment of the zero offset potential of the voltage measuring section 1 is insufficient, or if temperature drift occurs due to temperature change and the zero offset potential deviates, the measurement signal will have a small value. The microcomputer 3 is
This measurement signal is input and stored in internal RAM. Note that the zero offset value is the value obtained by subtracting the measurement signal corresponding to 0V from this measurement signal, but here the measurement signal corresponding to OV is expressed as a binary "0", so the captured measurement The signal can be stored as is as a zero offset value.

When the microcomputer 3 stores the measurement signal, the zero offset correction is canceled.

When the zero offset correction time is canceled, the measurement time starts, and the relay contact SW is opened and the relay contact SW2 is closed. The operation of these relay contacts SWl and SW2 is as follows:
It is controlled by a microcomputer 3.

In this state, when the voltage measurement terminal is connected to the object to be measured, the voltage of this object to be measured is input to the voltage measuring section 1. The voltage measuring section 1 A/D converts an input voltage and outputs a measurement signal corresponding to the voltage value. The microcomputer 3 takes in this measurement signal and performs zero offset.

That is, the zero offset value stored in the RAM is read out and addition/subtraction is performed on this measurement signal. Whether to add or subtract depends on the sign of the zero offset value. The measurement signal subjected to zero offset in this manner is output to the display section 2. The display section 2 displays the voltage value corresponding to the sent measurement signal.

Therefore, this voltage measuring device can set the zero offset value based on the accurate OV potential, and precise adjustment of the zero offset potential is not required. Furthermore, since the zero offset value can be set just before measurement with a simple operation, it is not affected by temperature drift.

[Embodiment 2] Another embodiment of the present invention will be described based on FIG. 2. Components having the same functions as those in the first embodiment will be denoted by the same reference numerals, and the explanation thereof will be omitted.

This embodiment shows a case where zero offset is performed by adding or subtracting a zero offset value to the input voltage of the voltage measuring section 1.

As shown in FIG. 2, the voltage measuring instrument of this embodiment includes a voltage measuring section 1, a display section 2, a control circuit 4, a latch circuit 5, a D/A
converter 6, differential amplifier 7, and relay contact SW,
・It is composed of S W t.

The output of the differential amplifier 7 is connected to one input of the voltage measuring section 1 . One input of the differential amplifier 7 and the other input of the voltage measuring section 1 are connected to a relay contact S.
A pair of voltage measurement terminals are connected via W + ·SW2. The relay contact SW is a normally closed contact connected in parallel to a pair of voltage measurement terminals, and can short-circuit one input of the differential amplifier 7 and the other input of the voltage measurement section 1. Relay contact SW2 is a normally closed contact connected in series between one voltage measurement terminal and one input of differential amplifier 7 connected thereto, and is configured to cut off input from this voltage measurement terminal. is now possible.

The output of the voltage measuring section 1 is connected to the display section 2. The display section 2 receives the measurement signal output from the voltage measurement section 1 as it is, and displays the corresponding voltage value.

A control output of the control circuit 4 is connected to a launch circuit 5. The launch circuit 5 is a circuit that is controlled by the control circuit 4 and stores the numerical value of a digital signal. The output of this latch circuit 5 is connected to a D/A converter 6. The D/A converter 6 is a circuit that converts the numerical value of the digital signal stored in the latch circuit 5 into a corresponding analog signal voltage and outputs the voltage. The output of this D/A converter 6 is connected to the other power of the differential amplifier 7. The differential amplifier 7 is a circuit that calculates the difference between these input voltages and outputs the difference.

Therefore, this differential amplifier 7 outputs the difference between the input voltage on the voltage measurement terminal side and the voltage from the D/A converter 6, thereby performing zero offset.

The operation of the voltage measuring instrument having the above configuration will be explained.

When the settings for zero offset correction are made, relay contact SW is first closed, relay contact SW2 is opened, and
The latch circuit 5 is reset to "0" by the control circuit 4. Therefore, the differential amplifier 7 outputs the difference between the O2 voltage shorted by the relay contact SWI and the digital signal corresponding to "0" converted into an analog voltage by the D/A converter 6. The output of this differential amplifier 7 is
The voltage is A/D converted by the voltage measuring section 1 and sent to the display section 2 for display. At this time, if the zero offset potentials of the voltage measuring section 1 and the D/A converter 6 are deviated, the display section 2 will be 0.
The voltage value of V is not displayed.

Therefore, a zero offset value is generated by changing the memory contents of the launch circuit 5 one step at a time until the voltage value displayed on the display section 2 becomes OV. Specifically, for example, while the operator is looking at the display on the display unit 2, the voltage value is OV.
If the value is larger, the memory content of the latch circuit 5 is set to “1”.
If the voltage value is smaller than Ov, the stored content of the latch circuit 5 is decreased by "1" to adjust the displayed voltage value to match Ov. do. Further, the zero offset value can also be automatically generated by inputting the measurement signal output from the voltage measuring section 1 to the control circuit 4 and having the control circuit 4 perform the same operation as described above. The displayed voltage value is OV
Or, when the measurement signal reaches a value corresponding to Ov,
The contents stored in the latch circuit 5 at that time become the zero offset value. Therefore, this zero offset value becomes a digital signal for the D/A converter 6 to obtain the voltage that should be input in order for the voltage measuring section 1 to output a measurement signal corresponding to OV.

The displayed voltage value is OV or the measurement signal is 0V
When the value corresponding to is reached, zero offset correction is canceled by operation or automatically. When the zero offset correction is canceled, the relay contact S is activated during measurement.
Wl opens and relay contact S W z closes. Note that the operations of these relay contacts SW + and SW are controlled by the control circuit 4 .

In this state, when the voltage measurement terminal is connected to the object to be measured, the voltage of this object to be measured passes through the differential amplifier 7 to the voltage measuring section 1.
is input. At this time, zero offset is performed by the differential amplifier 7 adding and subtracting the zero offset value stored in the launch circuit 5 to the input voltage in an analog manner. Therefore, the output of the voltage measurement section 1 becomes a measurement signal subjected to zero offset. The display section 2 displays the voltage value corresponding to this measurement signal.

In the case of this embodiment as well, the voltage measuring device can set the zero offset value based on an accurate 0V potential, and precise adjustment of the zero offset potential is not required. Furthermore, since the zero offset value can be set just before measurement with a simple operation, it is not affected by temperature drift.

[Embodiment 3] Still another embodiment of this embodiment will be described based on FIG. 3. Components having the same functions as those in the first and second embodiments will be denoted by the same reference numerals, and their explanations will be omitted.

This embodiment shows a case in which a zero offset is performed by adding and subtracting a measurement signal using a launch circuit 5 and an addition/subtraction section 8.

As shown in FIG. 3, the voltage measuring device of this embodiment is comprised of a voltage measuring section 1, a display section 2, a latch circuit 5, an addition/subtraction section 8, and a relay contact SWI-8W2.

A relay contact SW is provided on the input side of the voltage measuring section 1.

- A pair of voltage measurement terminals are connected via SW. The relay contacts sw and -sw have the same configuration as in the first embodiment.

The output of the voltage measuring section 1 is connected to one input of the adding/subtracting section 8. The addition/subtraction unit 8 is a circuit that performs zero offset by adding or subtracting the zero offset value of the other input to the measurement signal input from the voltage measurement unit 1. The output of the addition/subtraction section 8 is connected to the display section 2 and the latch circuit 5. The display unit 2 inputs the measurement signal subjected to the zero offset and displays the corresponding voltage value.

The launch circuit 5 is a circuit that is controlled by a control circuit (not shown) and stores the measurement signal output by the adder/subtractor 8 during zero offset correction, and the contents of this storage become the zero offset value. The output of the latch circuit 5 is connected to the other input of the adder/subtracter 8.

The operation of the voltage measuring instrument having the above configuration will be explained.

When the settings for zero offset correction are made, relay contact SWl closes, and relay contact SW! As it opens,
The latch circuit 5 is reset to "0" by a control circuit (not shown). Therefore, the voltage measuring section 1 has a relay contact S
It converts the Ov lightning voltage digital signal generated by the short circuit of W into a measurement signal and outputs it. If there is a deviation in the zero offset potential of the voltage measuring section 1, this measurement signal will become a signal that does not correspond to 0V. In addition, the addition/subtraction section 8 includes a child circuit 5.
Since "0" is the human power of the other, the measurement signal sent to one input is output as is. The measurement signal output from the adder/subtracter 8 is sent to the latch circuit 5 and stored. At this time, the measurement signal stored in the latch circuit 5 becomes the zero offset value. The zero offset value stored in the latch circuit 5 is not sent to the addition/subtraction unit 8 until the zero offset correction is canceled.

When the latch circuit 5 stores the zero offset value, the zero offset correction mode is canceled. When the zero offset correction is canceled, the relay contact SW,
opens, and relay contact SWt closes. The operations of these relay contacts SW and SW2 are controlled by a control circuit (not shown).

In this state, when the voltage measurement terminal is connected to the object to be measured, the voltage of this object to be measured is manually inputted to the voltage measuring section 1. The voltage measuring section 1 outputs a measurement signal corresponding to an input voltage. The addition/subtraction section 8 adds or subtracts the zero offset value from the latch circuit 5 to this measurement signal to perform zero offset. Therefore, the measurement signal input to the display section 2 is a signal subjected to zero offset. The display unit 2 displays the voltage (direct) corresponding to this measurement signal. During measurement, the measurement signal from the addition/subtraction unit 8 is not sent to the latch circuit 5; The zero offset value set at the time of zero offset correction is held.

In the case of this embodiment as well, the voltage measuring instrument can set the zero offset value based on the accurate OV potential, making precise adjustment of the zero offset potential unnecessary. Furthermore, since the zero offset value can be set just before measurement with a simple operation, it is not affected by temperature drift.

〔Effect of the invention〕

The zero offset correction device for a voltage measuring instrument according to the present invention includes:
As described above, in a voltage measuring instrument that converts the input voltage into a measurement signal in the voltage measurement section and displays it on the display section, there is a short-circuit switch that can short-circuit the input of the voltage measurement section, and a short-circuit switch that can short-circuit the input voltage during zero offset correction. a short-circuiting means for causing
When the short-circuiting switch is short-circuited by the short-circuiting means, when the input voltage of the voltage measurement section is measured at this time, addition and subtraction are added to the input voltage of the voltage measurement section or the measurement signal to make the measurement signal a value corresponding to Ov. zero offset value output means for outputting a zero offset value that can be used; storage means for storing the zero offset value outputted by the zero offset value output means; opening means for opening the short switch during measurement; When the input voltage of the voltage measurement section is measured when the voltage measurement section is open, the zero offset value stored in the storage means is read out, and the zero offset value is calculated by adding or subtracting the input voltage or measurement signal of the voltage measurement section at this time. The configuration has a zero offset means for performing this.

Thereby, accurate voltage measurement can be performed without compensating for zero offset or temperature drift of the voltage measurement section.

Therefore, the zero offset correction device for a voltage measuring instrument according to the present invention has a simple configuration that eliminates the need for precise adjustment of the zero offset potential in the voltage measuring section, and also eliminates the need for a circuit for compensating for temperature drift. It has the effect of being able to.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention, and is a circuit block diagram of a voltage measuring device. FIG. 2 shows another embodiment of the present invention, and is a circuit block diagram of a voltage measuring device. FIG. 3 shows still another embodiment of the present invention, and is a circuit block diagram of a voltage measuring device. FIG. 4 shows a conventional example, and is a circuit block diagram of a voltage measuring device. 1 is a voltage measuring section, 2 is a display section, and SW is a relay contact (short circuit switch).

Claims (1)

[Claims] 1. In a voltage measuring instrument that converts the input voltage into a measurement signal in the voltage measuring section and displays it on the display section, a shorting switch that can short-circuit the input of the voltage measuring section and a shorting means that short-circuits the shorting switch during zero offset correction. When the short-circuiting switch is short-circuited by the short-circuiting means, when the input voltage of the voltage measurement section is measured at this time, the measurement signal can be set to 0 by adding or subtracting the input voltage of the voltage measurement section or the measurement signal.
A zero offset value output means for outputting a zero offset value that can be a value corresponding to V, a storage means for storing the zero offset value outputted by the zero offset value output means, and an opening means for opening a short switch at the time of measurement. When the input voltage of the voltage measuring section is measured when the short-circuit switch is opened by the opening means, the zero offset value stored in the storage means is read out, and the input voltage or measurement signal of the voltage measuring section at this time is 1. A zero offset correction device for a voltage measuring instrument, comprising: zero offset means for performing zero offset by adding and subtracting.