JPS5937920Y2 - resistance measuring device - Google Patents

Description

[Detailed description of the invention] Technical field to which the invention pertains The present invention relates to a resistance measuring device for measuring the resistance value of a resistor located at a distance from a measuring circuit.

Description of the Prior Art Conventionally, in order to measure the temperature, etc. at a remote location in a factory or the like, a temperature sensor section equipped with a measuring resistor, etc. is disposed at the location to be measured, and the temperature sensor section and the remote location are connected to each other. Measurement is performed by connecting the device with an electric wire.

During this measurement, it is necessary to compensate for changes in the resistance value of the wire due to temperature fluctuations, changes over time, and the like.

Conventionally, a method of compensation using three electric wires has been generally used, but this method is often inconvenient when using existing wiring and is not economical because it requires a large amount of electric wires.

There is also a method of connecting two wires, but the circuit configuration on the temperature sensor side becomes complicated and reliability decreases.The operating temperature range is narrow due to the component parts (and furthermore, operation becomes difficult). There are disadvantages such as complexity.

Purpose of the invention The present invention simplifies the circuit configuration of the resistor side as a sensor part, enables highly reliable measurement even when the temperature of the measuring part is high, and provides an electric wire that connects the resistor and the measuring device. It is an object of the present invention to provide a resistance measuring device that can eliminate measurement errors caused by temperature change characteristics and the like.

The present invention includes a pair of electric wires connecting a measuring circuit position and a resistor position, and at the resistor position, one end of the resistor is connected to one of the pair of electric wires, and the resistor is connected to one end of the resistor at the resistor position. a diode connected between the other end of the body and the other of the pair of electric wires, and a diode having the same characteristics as the diode and having a polarity opposite to the diode with respect to the voltage generated between the pair of electric wires. with a diode connected so that
At the position of the measurement circuit, there is a power supply circuit that alternately switches and supplies a current in two directions, positive and negative, having the same absolute value to the pair of electric wires, and a power supply circuit that alternately supplies the pair of electric wires with positive and negative currents having the same absolute value. A circuit that generates a pulse width signal corresponding to the absolute value of the voltage generated between a pair of electric wires, and a connection time Q for two adjacent pulse width signals of this pulse width signal.
The present invention is characterized by comprising a circuit that calculates a difference.

. Explanation by example Hereinafter, this will be explained in detail with reference to examples.

The figure is a configuration diagram of an apparatus according to an embodiment of the present invention.

In the figure, 1 is a resistor to be measured, 2 and 3 are diodes, 4 is a wire pair, 5 is a power supply circuit, 6 is a differential amplifier, T is an inverting amplifier, 8 is an amplifier, 9 is a pulse width modulator, and 10 is a clock Input, 11 is a gate, and 12 is a counter.

The resistor 1 is connected to one end of a pair of wires 4 via a diode 2, and a diode 3 is coupled in parallel with the pair of wires 4.

The diodes 2 and 3 are selected to have the same characteristics, and also have the same temperature characteristics, aging characteristics, etc.

The other end of the wire pair 4 is coupled to the positive and negative inputs of a differential amplifier 6.

Further, a power supply circuit 5 is coupled to the wire pair 4, and switches a,
The configuration is such that constant current can be supplied in two directions, positive and negative, by the operation of b.

The output of amplifier 6 is coupled to an inverting amplifier 7 and an amplifier 80 input.

The inverting amplifier 7 and the amplifier 8 have the same gain and have input/output phase characteristics different by 180 degrees.

These outputs are sent to the pulse width modulator 9 via switches a and b.
This output is led to a counter 12 through a gate 11 along with a clock input 10.

Switch a is connected to the up and down terminals of the counter 12.
A voltage is conducted through b.

Here, each switch a and b are all interlocked, and a and b
are configured to open and close alternately.

To explain the measurement operation of the device configured in this way, when switch a is open and switch a is closed, wire pair 4
Since a constant current i flows in the direction shown by the solid arrow, diode 3 is not conductive, diode 2 is conductive, and current flows through resistor 1.

At this time, the voltage of the wire pair 4 at the input of the differential amplifier 60 is detected and amplified, and is applied to the pulse width modulator 9 via the amplifier 8.

A pulse duration signal proportional to the magnitude of this voltage is obtained by a pulse width modulator 9, and a gate 11 is opened to cause a counter 12 to count clock pulses by this duration.

At this time, since the counter 12 has an input to the up terminal due to the switch, counting is performed in the positive direction.

Next, each switch a, b is reversed, so that a closes and b opens.

In this state, a constant current i flows through the wire pair 4 in the direction of the dotted arrow, so the diode 2 is not conductive, the diode 3 is conductive, and the voltage of the wire pair 4 at this time appears at the input of the differential amplifier 60.

This is amplified and passed through amplifier γ to pulse width modulator 9
Similarly, it becomes a pulse time width signal and opens the gate 11.

This causes the clock pulse to pass from gate 11 to counter 1.
2 and counted by the counter 12.

At this time, since there is a signal at the down terminal from the switch a, the counter 12 counts in the negative direction.

As a result, the count value remaining on the counter 12 becomes proportional to the resistance value of the resistor 1.

By appropriately determining the gain of each amplifier, the constant of the pulse width modulator 9, the clock pulse period, and the value of the constant current i, the resistance value can be directly read and displayed on the counter 12.

That is, during the half cycle when switch a is open, wire pair 4,
The series resistance value of the diode 2 and the resistor 1 is measured, and the series resistance value of the wire pair 4 and the diode 3 is measured and subtracted in the next half cycle when the switch is open.

Since the diode 2 and the diode 3 have the same characteristics as described above, the result of subtraction indicates the resistance value of the resistor 1.

When the resistor 1 is used for temperature measurement, it is placed in a place where the temperature and other environmental conditions change drastically, but in the device of the present invention, the only circuit elements placed there are two diodes.

They are both subjected to the same changes in environmental conditions and exhibit the same electrical properties, resulting in the absence of complications and reliability and measurement accuracy over a wide range.

Furthermore, the measurement operation is simple, and automatic measurement can be performed in a short period of time.

Explanation of Effects Since the present invention has the above-mentioned configuration and operation, it has the following excellent features and has high practical value (1) The circuit configuration of the remote measuring end which is the sensor part is as follows: It has an extremely simple configuration that does not include any moving elements, and the temperature change characteristics of the coupled wire are reliably compensated for, so the reliability of its operation and mlJ determination can be improved.

In addition, since the only component other than the resistor is the diode, measurements can be made even under severe conditions within the upper temperature range in which the diode can operate normally. The measurement temperature range is wide.

Furthermore, since the sensor section is small, it is advantageous when the measured position is a narrow place.

(b) Since the electric wires used are two wires, it is economical and convenient when using existing wiring.

(c) By converting to a pulse time width signal, synchronous difference calculation can be performed with a simple circuit.

) The measurement operation of this device is simple, and accurate automatic measurements can be performed in a short time.

[Brief explanation of the drawing]

The figure is a configuration diagram of an apparatus according to an embodiment of the present invention. 1... Resistor to be measured, 2, 3... Diode, 4... Wire pair, 5... Power supply circuit, 6... Differential amplifier, 7... Inverting amplifier, 8... Amplifier, 9... Pulse modulator, 10... Clock input, 11...
・Gate, 12... Counter.

Claims (1)

[Claims for Utility Model Registration] In a resistance measuring device that remotely measures the resistance value of a resistor located at a location remote from the location of the measurement circuit, a pair of electric wires 4 connects the location of the measurement circuit and the location of the resistor. At the position of the resistor, one end of the resistor is connected to one of the l pairs of electric wires, and a diode 2 is connected between the other end of the resistor and the other of the pair of electric wires. and a diode 3 having the same characteristics as this diode and connected so that the voltage generated between the pair of electric wires has a polarity opposite to that of the class diode, and at the position of the measuring circuit. , a power supply circuit 5 which alternately switches and supplies a current in two directions, positive and negative, having the same absolute value between the pair of electric wires, and an input terminal is connected to each of the l pairs of electric wires, and amplifies the difference in voltage. A differential amplifier 6, and an amplifier T that amplifies the output of the differential amplifier with the same polarity or inverted polarity in response to switching of the current direction of the feeder circuit. 8, a pulse width modulator 9 that generates a pulse width signal corresponding to the output voltage of this amplifier, an AND gate 11 that receives this pulse width signal and a clock signal as two inputs, and an output terminal of this AND gate. Counting input terminal is connected,
A resistance measuring device comprising a counter 12 that counts the output pulses by switching them in a positive direction or a negative direction in accordance with the switching of the current direction of the power supply circuit Q.