JPH0618575A - Electric resistance measuring instrument - Google Patents

Abstract

PURPOSE:To measure the electric current of a sample kept under a heating condition with high accuracy irrespective of the stability of a measuring current and, at the same time, to measure a plurality of samples with a simple and inexpensive facility. CONSTITUTION:A DC circuit 10 which makes a DC current to flow to a sample is provided and, at the same time, a standard resistor 11 is connected in series to the circuit 10. The current values respectively generated in the sample and standard resistance are outputted by successively switching the values by means of a switch 17 and inputted to a CPU 14 after the values are converted into digital signals by means of an A/D converter 18. The CPU 14 calculates the value of the current flowing through the circuit 10 from the already known resistance of the resistor 11 and an input voltage signal and, at the same time, the electric resistance of the sample is calculated based on the calculated current value and the voltage value of the sample.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the electrical resistance of a sample that has been heated, and more specifically, it can accurately measure the electrical resistance of a sample by removing errors such as thermoelectromotive force. The present invention relates to an electric resistance measuring device.

[0002]

2. Description of the Related Art When an electric resistance is measured with high accuracy, a thermoelectromotive force or the like is generated at a contact point between a sample and a voltage detection circuit according to the sample temperature, and it is necessary to eliminate an error due to this. FIG. 7 is a block diagram showing a conventional electric resistance measuring apparatus of this type, and FIG. 8 is a timing chart for explaining the operation of the apparatus. The sample S is heated to the required temperature in the electric furnace 50. An intermittent DC current (FIG. 8, i) is caused to flow from the current generator 51 to the sample S, and the voltage generated between the two points of the sample S is output via the amplifier 52. This voltage output is further amplified by the amplifier 52 and then input to the first sample hold circuit 54. The first sample-and-hold circuit 54 samples the voltage between the direct current to the sample S is cut off (Fig. 8, e _n). This sampled voltage is due to the thermoelectromotive force caused by temperature changes and the like. Therefore, by negatively feeding back this voltage value via the integrating circuit 55, it is possible to remove the error component due to the thermoelectromotive force from the output of the amplifier 53. Therefore, the voltage amplified output while the direct current is flowing through the sample S is sampled by the second sample hold circuit 56 (see FIG. 8,
e ₀ ), when smoothed by the filtering circuit 57, a voltage output proportional to the resistance between the two points of the sample S is obtained at the output terminal 58. By reading this output with an indicating instrument, the sample S
The electrical resistance of can be calculated. Reference numeral 59 is a timing signal generation circuit, and each sample hold circuit 5
4, 56 and the operation timing signal of the current generator 51 are output.

[0003]

According to the above-mentioned conventional electric resistance measuring device, the resistance value of the sample S is determined by Ohm's law from the voltage value obtained at the output terminal 58 and the direct current value flowing in the sample S. Can be calculated. Here, the direct current flowing through the sample S serves as a reference for calculating the resistance value,
High stability must be maintained during the measurement. However, such a highly stable current generator is expensive and it is difficult to highly stabilize the current value due to a transient phenomenon when the power is turned on and off. Therefore,
The conventional electrical resistance measuring device described above has a problem that it is difficult to obtain a highly reliable measurement result.

Further, in the above-mentioned conventional electric resistance measuring device,
The circuit system shown in Fig. 7 is required for one sample to be measured. If you want to measure multiple samples at once, you need to prepare the circuit system shown in Fig. 7 for each sample. There was a problem that the cost was high.

The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to obtain a highly accurate measurement result regardless of the stability of the measurement current, and to use a plurality of samples in a simple and inexpensive facility. An object of the present invention is to provide an electric resistance measuring device that can be measured by.

[0006]

In order to achieve the above object, an electric resistance measuring apparatus of the present invention comprises a current generator for generating a direct current and a direct current circuit for flowing the direct current from the current generator to a sample. A standard resistance connected in series to the DC circuit, a sample voltage amplifier for amplifying the voltage generated between two points of the sample, and a standard voltage amplifier for amplifying the voltage generated across the standard resistance, A switch for switching and outputting the input from the sample voltage amplifier and the input from the standard voltage amplifier; an analog / digital converter for digitally converting the output from the switch to output; and a current generator. The switch is turned on and off intermittently, and a predetermined switching operation is performed on each input contact of the switching device while the current generator is in an on state and an off state. A central processing unit for calculating the electrical resistance of the sample based on the input from the exchanger, a configuration equipped with. Further, in order to measure a plurality of samples, in the invention of claim 2, a plurality of samples are connected in series to the DC circuit, and sample voltage amplifiers for amplifying a voltage generated between two points in each sample are provided. The switching device is provided with input contacts from these sample voltage amplifiers, and the central processing unit calculates the electrical resistance of each sample based on the input signal from the analog-digital converter. Further, in the invention of claim 3, a plurality of circuit systems each including the current generating circuit, the direct current circuit, the standard resistor, the sample voltage amplifier, and the standard voltage amplifier are provided, and the switching device includes:
An input contact from each sample voltage amplifier and each standard voltage amplifier is provided, and the central processing unit calculates the electrical resistance of each sample in each circuit system based on the input signal from the analog-digital converter. is there.

[0007]

[Operation] When a DC current is intermittently applied from the current generator to the sample and standard resistance inserted in the DC circuit, a voltage proportional to the resistance value is generated between two points of the sample and both ends of the standard resistance. . These voltages are amplified and taken out by a sample voltage amplifier and a standard voltage amplifier, respectively. Then, each voltage-amplified output when the DC circuit is turned on is individually output to the analog / digital converter by the operation of the switching device and input to the central processing unit. Then, the sample voltage amplification output when the DC circuit is not conducted is output to the analog-digital converter by the operation of the switching device and input to the central processing unit.

In the central processing unit, the current value I _S flowing in the DC circuit is calculated on the basis of the voltage signal Vs when the DC circuit is conducting with respect to the input standard resistance. Here, assuming that the resistance value of the standard resistance is R _S , I _S is obtained by the following equation. I _S = V _S / R _S (I) Next, the electrical resistance of the sample is calculated based on the calculated current value I _S and the voltage signal of the sample when the DC circuit is conducting and non-conducting. That is, the sample voltage signal V _m when the DC circuit is conducting includes the voltage value V _t due to the thermoelectromotive force in addition to the voltage value V ₀ due to the electrical resistance R of the sample (that is, V _m = V ₀ + V _t). ). On the other hand, when the current circuit is not conducted, the voltage value V ₀ due to the electrical resistance of the sample becomes 0,
The input voltage signal at this time is only the voltage value V _t due to the thermoelectromotive force. Therefore, in the central processing unit, the electrical resistance R of the sample can be calculated by the following equation. R = (V _m −V _t ) / I _S = {(V ₀ + V _t ) −V _t } /
I _S ... (II)

When measuring a plurality of samples, the voltage output of each sample inserted in the DC circuit is individually input to the central processing unit by a switch, and the above-mentioned calculation is performed for each sample. The electrical resistance of the sample can be determined.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an electric resistance measuring apparatus according to a first embodiment of the present invention. The electric resistance measuring apparatus of the present embodiment is provided with one circuit system in which a sample S and a standard resistance 11 are connected in series to a DC circuit 10 and a DC current is caused to flow by a current generator 12. The sample S is heated to a predetermined temperature in the electric furnace 13, and the electric resistance under the heating is measured by the apparatus of this embodiment. The standard resistor 11 has a constant resistance value R _S. The current generator 12 is a DC circuit 10
A constant DC current is intermittently applied to the. The on / off control of the current generator 12 is performed by the central processing unit 14 as described later.

A sample voltage amplifier 15 is connected between two points of the sample S via a voltage detection lead wire. A standard voltage amplifier 16 is also connected between both ends of the standard resistor 11. The output sides of these voltage amplifiers 15 and 16 are connected to the input terminals s and 1 of the switch 17, respectively. Switch 1
The output terminal a of 7 is an analog-digital converter (hereinafter,
Central processing unit 1 via A / D converter 18
4 is connected.

The central processing unit 14 controls the current generator 12 to be turned on and off at regular time intervals, and also has a switching unit 17
Control the switching operation of. The central processing unit 14 may be composed of a dedicated microcomputer or a general-purpose personal computer.

Next, the operation of the electric resistance measuring apparatus according to the first embodiment described above will be described with reference to FIGS. 1 and 2.
FIG. 2 is a timing chart for explaining the operation of the device. Under the control of the central processing unit 14, the current generator 12 is first turned on, and a direct current is passed through the standard resistor 11 and the sample S. The voltage values V _S and V _m of the standard resistor 11 and the sample S in this conducting state are amplified by the amplifiers 15 and 16 and sent to the input terminals s and 1 of the switch 17. Then, during the conducting state (T _{ON in} FIG. 2), the switching unit 17 is switched by the control of the central processing unit 14, and the input terminals s and 1
The voltage outputs V _S and V _m input to the A / D converter 18
Are sequentially output to.

Next, the current generator 12 is turned off. At this time, a voltage Vt due to a thermoelectromotive force is generated between two points of the sample S, and this voltage Vt is applied to the sample voltage amplifier 15
Amplified by and sent to the input terminal 1 of the switch 17. Then, during the non-conducting state (T _{OFF in} FIG. 2), the switching device 17 is switched under the control of the central processing unit 14, and the voltage output Vt input to the input terminal 1 is converted into the A / D converter 18
Output to.

The A / D converter 18 outputs each voltage output V
_{The S} , V _m , and V _t are converted into digital signals and sent to the central processing unit 14. In the central processing unit 14, first, the standard resistance 11
Based on the resistance value Rs and the standard voltage value VS during conduction,
The current value IS flowing in the DC circuit 10 is calculated by the equation (I). Then, based on this current value I _S and the voltage values V _m and V _t of the sample S when the DC circuit 10 is conducting and non-conducting, the electric resistance of the sample S is calculated by the formula (II). When the electric resistance of the sample at various temperatures is measured by changing the heating temperature of the sample, the above operation may be repeated for each of various set temperatures.

As described above, the data regarding the electric resistance of the sample S calculated by the central processing unit 14 can be directly output to other sample measurement-related equipment by a digital signal without an interface.

FIG. 3 is a block diagram showing an electric resistance measuring apparatus according to a second embodiment of the present invention, FIG. 4 is a flow chart for explaining the operation of the apparatus, and FIG. 5 is a timing chart. The electric resistance measuring apparatus of the second embodiment collectively measures the electric resistance of a plurality of samples S _{1 to} S _n , and the DC circuit 10 in the apparatus shown in the first embodiment (see FIG. 1) is used. In addition, each of the samples S _{1 to} S _n is inserted in series. Each of the samples S _{1 to} S _n has a sample voltage amplifier 15 ₁ for amplifying a voltage generated between two points.
~ 15 _n are connected. Further, the switch 17 is provided with input terminals ₁ to _n corresponding to the outputs of the amplifiers 15 ₁ to 15 _n . As described above, according to the electric resistance measuring apparatus of the present invention, the electric resistance of a plurality of samples can be measured at low cost simply by adding the voltage amplifier and the input contact of the switching unit 17.

Next, the operation of the above-described electric resistance measuring device will be described (see FIGS. 4 and 5). Under the control of the central processing unit 14, first, the current generator 12 is turned on (FIG. 4, ST1), and a direct current is passed through the standard resistor 11 and each of the samples S _{1 to} S _n . The standard resistor 11 and the voltage values VS and V _{m1 to} V _mn of the samples S _{1 to} S _n in this conducting state are set to the amplifiers 1 respectively.
It is amplified by 6, 15 ₁ to 15 _n and sent to the input terminals s, ₁ to _n of the switch 17. Then, during the conducting state (T _{ON in} FIG. 5), the switching unit 17 is controlled by the central processing unit 14.
(FIG. 4, ST2, ST4), and the voltage outputs V _S , V _{m1 to} V _mn input to the input terminals s and 1 to n are A / D.
The signals are sequentially output to the converter 18 (ST3, ST5 in FIG. 4).

Next, the current generator 12 is turned off (ST6 in FIG. 4). At this time, voltages V _{t1 to} V _tn due to thermoelectromotive force are generated between the two points of the samples S _{1 to} S _n , respectively, and these voltages V _{t1 to} V _tn are applied to the sample voltage amplifiers 15 respectively.
Each input terminal 1 of the switch 17 is amplified by ₁ to 15 _n
Send to ~ n. Then, during the non-conduction state (T _{OFF in} FIG. 5)
Then, the switching device 17 is switched by the control of the central processing unit 14 (ST7 in FIG. 4), and the voltage outputs V _{t1 to} V _tn input to the input terminals 1 to n are output to the A / D converter 18 ( Figure 4, ST8).

The A / D converter 18 outputs each voltage output V
_S , V _{m1 to} V _mn , V _{t1 to} V _tn are converted into digital signals and sent to the central processing unit 14. In the central processing unit 14, first, based on the resistance value R _S of the standard resistor 11 and the standard voltage V _S at the time of conduction, the current value I _S flowing in the DC circuit 10 is calculated by the above formula (I) (FIG. 4, ST9). ). Then, based on this current value I _S and each voltage V _{m1 to} V _mn , V _{t1 to} V _tn when the DC circuit 10 relating to the sample is conducting and non-conducting, each sample S _{1 to} S is expressed by the formula (II). Calculate the electrical resistance of _n . When the electric resistance of the sample is measured at various temperatures by changing the heating temperature of the sample, the above operation may be repeated for various set temperatures.

FIG. 6 is a block diagram showing an electric resistance measuring apparatus according to the third embodiment of the present invention. In this embodiment, a plurality of circuit systems including the current generator, the DC circuit 10, the standard resistor 11, the sample voltage amplifiers 15 ₁ to 15 _n , and the standard voltage amplifier 16 shown in the second embodiment are provided. each sample collector amplifier 15 to the switch _{17 1 ~15 n, 15 1 ~15} n
In addition, the input contacts from the standard voltage amplifiers 16 and 16 are provided. Here, as a sample to be inserted into the DC circuit 10 in each circuit system, it goes without saying that various samples for which electric resistance is to be obtained can be arbitrarily selected.

Also in the apparatus of this embodiment, the central processing unit 1
By turning on / off each of the current generating circuits 12 and 12 under the control of No. 4 and switching the switching device 17, the standard voltage V _S , each sample voltage V _m when the current is conducting, and each of the non-conducting currents The sample voltage V _t and the sample voltage V _t are sequentially input to the central processing unit 14, the standard current I _S is obtained based on these input signals, and then the electrical resistance R of each sample is calculated.

The present invention is not limited to the above-described embodiments, but various modifications and applications are possible without changing the gist. Further, the electrical resistance measuring device of the present invention can be applied not only to a sample of an electrical thermal analysis device, but also to a contact resistance of a relay contact, a contact resistance of a metal, and the like.

[0024]

As described above, according to the present invention, since the measured current value is calculated by the standard resistor 11, even if the current value is unstable, the sample can be accurately measured based on the calculated data. The electrical resistance of can be calculated. Further, it is an effect that the electrical resistances of a plurality of samples can be collectively measured simply and inexpensively by simply adding the input contacts of the sample voltage amplifier 15 and the switching device 17.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electric resistance measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the device.

FIG. 3 is a block diagram showing an electric resistance measuring device according to a second embodiment of the present invention.

FIG. 4 is a flowchart for explaining the operation of the device.

FIG. 5 is also a timing chart.

FIG. 6 is a block diagram showing an electric resistance measuring device according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a conventional example.

FIG. 8 is a timing chart for explaining the operation of the conventional example.

[Explanation of symbols]

 10 DC circuit 11 Standard resistance 12 Current generator 13 Electric furnace 14 Central processing unit 15 Sample voltage amplifier 16 Standard voltage amplifier 17 Switching device 18 Analog-digital converter

Claims (3)

[Claims] 1. A current generator for generating a direct current, a direct current circuit for supplying a direct current from the current generator to a sample, a standard resistance connected in series to the direct current circuit, and a point between two points of the sample. A sample voltage amplifier that amplifies the voltage generated at the reference voltage, a standard voltage amplifier that amplifies the voltage generated at both ends of the standard resistance, and outputs by switching the input from the sample voltage amplifier and the input from the standard voltage amplifier. A switch, an analog-to-digital converter that digitally converts the output from the switch and outputs the output, and the current generator is turned on and off intermittently, and while the current generator is on and off. A central processing unit that performs a predetermined switching operation for each input contact of the switching device during each of the steps and calculates the electrical resistance of the sample based on the input from the analog-digital converter; Electric resistance measuring apparatus characterized by comprising a. 2. The electric resistance measuring device according to claim 1, wherein a plurality of samples are connected in series to the DC circuit,
A sample voltage amplifier for amplifying a voltage generated between two points in each sample is provided respectively, and the switching device is provided with an input contact from these sample voltage amplifiers, and the central processing unit is provided with the analog-digital converter. An electric resistance measuring device characterized by calculating the electric resistance of each sample based on the input signal of. 3. The electric resistance measuring device according to claim 1, wherein a plurality of circuit systems each including the current generator, the direct current circuit, the standard resistance, the sample voltage amplifier, and the standard voltage amplifier are provided, and the switching device includes: Input contacts from the sample voltage amplifiers and the standard voltage amplifiers are provided, and the central processing unit determines the electrical resistance of each sample in each circuit system based on the input signal from the analog-digital converter. An electric resistance measuring device characterized by calculating.