JP2013186523A - Resistance generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a degree of freedom in design by using electronic components having a wide selection and easily available for an arithmetic logical unit that performs multiplication of a simulated resistance value and current for measurement.SOLUTION: A resistance generating device sets a predetermined simulated resistance value R for an ohmmeter as an apparatus to be calibrated, outputs a voltage Vout which is a product of current for measurement IM supplied from a current source included in the ohmmeter and the simulated resistance value R, and provides the voltage Vout to the ohmmeter. The resistance generating device comprises: output terminals T1 and T2 through which the current for measurement IM is inputted from the ohmmeter and the voltage Vout is outputted to the ohmmeter; a resistance value setting unit 11 for setting the simulated resistance value R and outputting the simulated resistance value R as a digital value; and an arithmetic logical unit 12 for multiplying the simulated resistance value R from the resistance value setting unit 11 by an A/D converted value of the current for measurement IM inputted from the ohmmeter and outputting the voltage Vout to the output terminals T1 and T2. The arithmetic logical unit 12 includes a microcomputer.

Description

  The present invention relates to a resistance generator, and more particularly to a resistance generator used for calibration and operation check of a resistance meter such as a resistance temperature detector type thermometer.

  In recent years, in order to calibrate an ohmmeter, a resistance generator that equivalently generates a virtual resistance using electronic means has been used instead of a solid standard resistor. Patent Document 1 proposes an electric quantity generator that generates not only its equivalent resistance but also electric quantities such as voltage and current at arbitrary values, and its configuration is shown in FIG.

  As a basic configuration, this electric quantity generator has a multiplying D / A converter 30 that multiplies a pulse width corresponding to a set value D and an input voltage, and a voltage and current generated by the D / A converter 30. Alternatively, the output terminals 51 and 52 for extracting a voltage corresponding to the equivalent resistance, the reference voltage source 10 connected to the D / A converter 30 when a voltage or current is generated, and the output terminals 51 and 52 when the equivalent resistance is generated. And a current-voltage converter 70 that converts the measurement current Im from the ohmmeter into a voltage and applies it to the D / A converter 30. Reference numeral 40 denotes an output circuit, and 60 denotes an output switching circuit.

  When resistance is generated (when the resistance meter is calibrated), a predetermined simulated resistance value R is input to the D / A converter 30 as the set value D, and the switch 20 is switched to the contact 22 on the current-voltage converter 70 side. In addition, a resistance meter (not shown) is connected between the output terminals 51 and 52, and the measurement current Im supplied from the constant current source IS included in the resistance meter is converted into a voltage by the current-voltage converter 70 to be converted into D / D. Input to the A converter 30.

  As a result, the voltage Vout of R × Im is output from the D / A converter 30 to the output terminals 51 and 52 via the output circuit 40, so that the simulated resistance value (virtual resistance value) is used without using a solid standard resistor. The resistance value R can be used to calibrate the ohmmeter and check the operation.

JP-A-9-160659

  In the electric quantity generator described in Patent Document 1, a multiplying type is used for the D / A converter 30; however, there are very few types of multiplying D / A converters currently available on the market. This is a design constraint. Further, the response speed of the time division multiplying D / A converter is relatively low.

  On the other hand, in a thermometer using a resistance temperature detector (resistance temperature detector type thermometer), in order to reduce the influence of self-heating due to the current flowing through the resistance temperature detector, the measurement current is often made into a rectangular wave shape. However, a generator with a slow output response is not preferable for the calibration of such a thermometer.

  Therefore, an object of the present invention is to employ an electronic component having a wide range of choices and easy to obtain for the calculation unit that multiplies the simulated resistance value and the measurement current, thereby increasing the degree of design freedom and fast output response. An object of the present invention is to provide a resistance generator suitable for calibration of a resistance temperature detector type thermometer.

  In order to solve the above problems, the present invention sets a predetermined simulated resistance value R for an ohmmeter that is a device to be calibrated, and a measurement current IM supplied from a current source of the ohmmeter and the simulated resistance. In a resistance generator that outputs a voltage Vout (= IM × R), which is a product of the value R, and applies it to the ohmmeter, the ohmmeter is connected, and the measurement current IM is input from the ohmmeter. A pair of output terminals for outputting the voltage Vout to the ohmmeter, the simulated resistance value R is set, a resistance setting unit for outputting the simulated resistance value R as a digital value, and output from the resistance setting unit And an arithmetic unit that multiplies the simulated resistance value R and the A / D conversion value of the measurement current IM input from the ohmmeter and outputs the voltage Vout to the pair of output terminals, Microphone in computing unit It is characterized by using a computer.

  According to a preferred aspect of the present invention, a current-voltage converter, a peak value detection circuit, and an A / D converter that convert the measurement current IM into a voltage between the input side of the arithmetic unit and the one output terminal. An input side circuit including a converter in series is connected, and an output side circuit including a D / A converter is connected between the output side of the arithmetic unit and the other output terminal.

  More preferably, the measurement current IM is a rectangular wave, an output switch connected between the D / A converter of the output side circuit and the other output terminal, and a rising edge of the rectangular wave , And a switch control unit that detects each falling edge or each level of high level and low level and controls on / off of the output switch, and is synchronized with the measurement current IM between the output terminals. It is preferable that the voltage Vout of a rectangular wave appears.

  According to the present invention, the multiplication of the simulated resistance value and the measurement current is performed not by the multiplication type D / A converter but by a microcomputer having a wide range of choices and easy to obtain. The degree of freedom is increased.

  In addition, when the measurement current supplied from the ohmmeter is a rectangular wave, high-speed response is required, but the part related to the high-speed response is turned on at the rising edge of the square wave and the rectangular wave, and turned off at the falling edge. By using the output switch, the A / D converter and the D / A converter can be replaced with a relatively low-speed and inexpensive converter.

The schematic diagram which shows embodiment of the resistance generator by this invention. The circuit diagram which shows the electric quantity generator including the resistance generation function which concerns on a prior art.

  Next, an embodiment of the present invention will be described with reference to FIG. 1, but the present invention is not limited to this.

  As shown in FIG. 1, the resistance generator 10 has a basic configuration in which a resistance value setting unit 11 in which a simulated resistance value R is set by a user (operator), a calculation unit 12, and a pair of output terminals. T1 and T2, and an ohmmeter (not shown) as a device to be calibrated is connected between the output terminals T1 and T2.

  The resistance value setting unit 11 gives the simulated resistance value R set by the user to the calculation unit 12 as a digital value. The simulated resistance value R is arbitrarily selected from the allowable generation range of the resistance generator 10.

  The ohmmeter connected between the output terminals T1 and T2 includes a constant current source that internally generates a measurement current, and at the time of calibration, the resistance generator 10 has a constant current measurement current from the output terminals T1 and T2. Supply IM. In this embodiment, the resistance meter is a thermometer using a resistance temperature detector as a sensor (resistance temperature detector type thermometer), and the measurement current IM is a rectangular wave current.

  The calculation unit 12 includes a second input port 12b in addition to the first input port 12a to which the resistance value setting unit 11 is connected. In this embodiment, the calculation unit 12 is provided between the second input port 12b and the output terminal T2. An input side circuit including a current-voltage converter 13, a peak value detection circuit 14, and an A / D converter 15 in series is connected.

  The current-voltage converter 13 converts the measurement current IM from the ohmmeter into a voltage. Therefore, although the voltage corresponding to the measurement current IM is output from the current-voltage converter 13, for convenience of explanation, the output may be referred to as the measurement current IM instead of the measurement voltage.

  The peak value detection circuit 14 detects the peak value of the measurement current IM. The A / D converter 15 converts the peak value detected by the peak value detection circuit 14 into a digital value and provides it to the second input port 12 b of the computing unit 12.

  The computing unit 12 multiplies (R × IM) the simulated resistance value R input from the first input port 12a and the measured current IM input from the second input port 12b, and outputs the voltage Vout (= IM × R) is output, but in the present invention, a microcomputer is used for the calculation unit 12.

  Also in this specification, the microcomputer is defined as an IC (integrated circuit) called a so-called one-chip microcomputer in which a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory) and the like are integrated into one chip. Is done.

  In this embodiment, an output side circuit including a D / A converter 16, an output amplifier 17, and an output switch 18 in series is connected between the output port 12c of the arithmetic unit 12 and the output terminal T1.

  The D / A converter 16 converts the voltage Vout (= IM × R) output as a digital value from the arithmetic unit (microcomputer) 12 into an analog value. The output amplifier 17 amplifies the output level of the D / A converter 16 to a predetermined level.

  The output switch 18 is a switch for outputting the voltage Vout as a rectangular wave synchronized with the rectangular wave measuring current IM supplied from the resistance meter.

  Therefore, in this embodiment, a comparator 19 that detects the rise and fall of the measurement current IM is connected to the output side of the current-voltage converter 13, and the output of the output switch 18 is controlled by the comparator 19. Like to do.

  That is, the output switch 18 is turned on at the rise time of the measurement current IM and turned off at the fall time, and thereby the voltage Vout from the output switch 18 is synchronized with the rectangular wave measurement current IM supplied from the resistance meter. Output as a square wave.

  As another example, the output switch 18 may be controlled so as to be turned off at the rise time of the measurement current IM and turned on at the fall time, for example. The measurement current IM may be controlled to be on at a high level, off at a low level, off at a high level, and on at a low level.

  Next, a series of operations of the resistance generator 10 according to this embodiment will be described.

  First, the user sets a predetermined simulated resistance value R in the resistance value setting unit 11. Further, a resistance meter (temperature measuring resistance type thermometer) (not shown) as a device to be calibrated is connected to the output terminals T1 and T2, and a rectangular wave measuring current IM is supplied to the resistance generator 10 from the resistance meter.

  The measurement current IM is converted into a voltage by the current-voltage converter 13 and input to the peak value detection circuit 14. The peak value detection circuit 14 captures and holds the peak value of the rectangular wave signal. The A / D converter 15 converts the peak value output from the peak value detection circuit 14 into a digital value, and supplies the digital value to the arithmetic unit 12 including a microcomputer.

  The computing unit 12 calculates the voltage Vout (= R × IM) from the simulated resistance value R set in the resistance value setting unit 11 and the measurement current IM from the A / D converter 15, and outputs the output port 12c. Output from.

  The voltage Vout is converted to an analog value by the D / A converter 16, amplified to a predetermined level by the output amplifier 17, and then input to the output switch 18.

  Since the output switch 18 is turned on by the comparator 19 at the rise of the measurement current IM and turned off at the fall, the voltage Vout is output from the output switch 18 as a rectangular wave synchronized with the measurement current IM.

  In this manner, when a rectangular wave voltage Vout synchronized with the measurement current IM appears between the output terminals T1 and T2, calibration, operation check, and the like are performed on the ohmmeter side based on the voltage Vout.

  As can be seen from the description of the above embodiment, according to the present invention, multiplication of the simulated resistance value R and the measurement current IM is not performed by a multiplying D / A converter, but a microcomputer with a wide range of choices and easily available. By doing so, the freedom degree of the design including the calculating part 12 is raised.

  In addition, when the measurement current IM supplied from the ohmmeter is a rectangular wave, high-speed response is required, and the part related to the high-speed response is turned on and off at the rising edge of the rectangular wave and the peak value detection circuit 14. By using the output switch 18 that is turned off at this time, the A / D converter 15 and the D / A converter 16 can be replaced by a relatively low-speed and inexpensive converter.

  In the above embodiment, the measurement current IM supplied from the ohmmeter side is a rectangular wave. However, the measurement current IM may be a linear constant current. In this case, the peak value detection circuit 14, the output switch 18, and the comparator 19 may be omitted.

DESCRIPTION OF SYMBOLS 10 Resistance generator 11 Resistance value setting part 12 Calculation part (microcomputer)
13 Current-Voltage Converter 14 Peak Value Detection Circuit 15 A / D Converter 16 D / A Converter 17 Output Amplifier 18 Output Switch 19 Comparator T1, T2 Output Terminal

Claims (3)

A predetermined simulated resistance value R is set for an ohmmeter that is a device to be calibrated, and a voltage Vout (=) is a product of a measurement current IM supplied from a current source of the ohmmeter and the simulated resistance value R. In the resistance generator that outputs (IM × R) to the resistance meter,
The resistance meter is connected, the measurement current IM is input from the resistance meter, a pair of output terminals for outputting the voltage Vout to the resistance meter, and the simulated resistance value R are set. A resistance value setting unit that outputs the simulated resistance value R as a digital value, the simulated resistance value R output from the resistance value setting unit, and the A / D conversion value of the measurement current IM input from the resistance meter, And a calculation unit that outputs the voltage Vout to the pair of output terminals, and the calculation unit uses a microcomputer.   An input side circuit including a current-voltage converter for converting the measurement current IM into a voltage, a peak value detection circuit, and an A / D converter in series between the input side of the arithmetic unit and the one output terminal 2. An output side circuit including a D / A converter is connected between the output side of the arithmetic unit and the other output terminal. Resistance generator.   The measurement current IM is a rectangular wave, an output switch connected between the D / A converter of the output side circuit and the other output terminal, and rising and falling edges of the rectangular wave Or a switch control unit for detecting ON and OFF of the output switch by detecting each of the high level and the low level, and the rectangular-wave voltage Vout synchronized with the measurement current IM between the output terminals. The resistance generator according to claim 2, wherein: appears.

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