JPH0413979A - Resistance value measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the measurement of a resistance value even in a short time and accurately by arranging a constant current source to run a constant current to an object desired to measure a resistance value, an A/D converter to convert a voltage across the object to be measured into a digital data and a control/arithmetic circuit which calculates and outputs the resistance value. CONSTITUTION:A switch 12 is interposed between an object 1 to be measured and a constant current source 11 which runs a constant current I to the object 1 desired to measure a resistance value R. An A/D converter 13 converts a voltage V across the object 1 to be measured into a digital data. A control/ arithmetic circuit 15 controls an amplifier 14 of a gain 1 for matching impedance interposed between the object 1 to be measured and the A/D converter 13, the switch 12 and the A/D converter 13 to perform a computation by a specified system. The control/arithmetic circuit 15 is given information beforehand to determine the necessity of judging whether the voltage V is in vibration or not. This enables the measurement of a resistance value R in a short time and accurately even when the resistance value R of the object 1 to be measured is large.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an apparatus for measuring the resistance value of an object to be measured, such as a resistor.

``Prior Art'' Conventionally, such a resistance value measuring device includes a constant current source 51 that flows a constant current I through the object to be measured 1 whose resistance value R is to be measured, as shown as a device 50 in FIG. A switch 52 inserted between the constant current source 51 and the object to be measured 1, the object to be measured 1
An A/D that converts the voltage between both ends of the
A converter 53, an amplifier 54 with a gain of 1 for impedance matching inserted between the device under test 1 and the A/D converter 53, and a control circuit 55 for controlling the switch 52 and the A/D converter 53. With the object 1 connected to the device 50, the control circuit 55 turns on the switch 52 at time to as shown in FIG.
By supplying the measurement signal SP from 5 to the A/D converter 53, the A/D converter 53 converts the voltage across the object 1 to digital data, and calculates the resistance value of the object 1 from the digital data. A method for finding R is being considered.

That is, as shown in FIG. 7, the voltage ■ is determined by the time constant C- formed by the resistance value R of the device under test 1 and the input capacitance C at the point where the device under test 1 is connected from the time point to, as shown in FIG.
R increases as an exponential function and reaches the final value R・■ at time tχ after time Tx determined by time constant C−R. Therefore, by setting the above time ty after time tx, A/D
In the converter 53, (J
The resistance value R can be determined by determining R·■ as digital data and dividing it by the known constant current ■.

"Problem to be Solved by the Invention J" However, in the conventional resistance value measuring device described above, the voltage across the object to be measured 1 from the time to when the switch 52 is turned on due to the resistance value R of the object to be measured 1 is If the time Tχ until the time point tx when ■ reaches the final value R-1 changes and the resistance value R becomes large, the time Tx becomes longer, so the resistance value R
If is large, a long time must be allowed for the time Tx, and there is an inconvenience that it takes a long time to measure the resistance value R.

SUMMARY OF THE INVENTION Therefore, the present invention provides a device for measuring the resistance value of an object to be measured such as a resistor, which can measure the resistance value of the object to be measured in a short time and accurately even when the resistance value of the object to be measured is large. This is what I did.

[Means for Solving the Problems] The invention according to claim 1 includes a constant current source that flows a constant current () through an object to be measured whose resistance value R is to be measured, and a voltage across the object to be measured as digital data. In addition to the A/D converter that converts the current to the object under test, the time required for the voltage across the object to reach the final value R-1 from the time when the current starts flowing from the constant current source to the object under test is Voltage across the object to be measured at a first time point after a sufficiently short predetermined time and a second time point after the predetermined time period from this first time point ■1
and ■2 are obtained as digital data from the above A/D converter, and from the digital data V+"/I
(2V1-V2) and convert it into the above resistance value R
A control calculation circuit is provided that outputs as follows.

In the invention of claim 2, in addition to a resistor (a constant current source that flows a constant current I to the object to be measured whose iR is to be measured, and an A/D converter that converts the voltage across the object to be measured into digital data) and a first one after a predetermined time sufficiently shorter than the time required for the voltage across the object to reach the final value R-1 from the time when the current starts flowing from the constant current source to the object to be measured. a voltage V1 across the object to be measured at a second time point after the predetermined time period from the first time point, and a third time point after the predetermined time period from the second time point;
V2 and v3 are obtained as digital data from the A/D converter, and from the digital data (vz
-V, )/Vl and (■IVZ)/(vz -V
1), and when this ratio or difference is within a certain range, Vl2 is calculated from the above digital data.
/I (2v, -y2) and outputs it as the resistance value R. If the ratio or difference is not within the certain range, the voltage across the object to be measured becomes the final value R. The voltage across the object under test at the fourth point after the time when it is expected to reach −1 is the voltage
A control calculation circuit is provided which obtains digital data from the /D converter, calculates v a / r from the digital data, and outputs this as the resistance value R.

"Function" When a current is passed through the object to be measured from the constant current source of the resistance value measuring device, if the voltage V across the object does not oscillate, the voltage The time constant C formed by the resistance value R of the object to be measured and the input capacitance C at the point where the object to be measured of the device is connected from the time point to when the object starts flowing.
-R as an exponential function and reaches the final value R-1 at time tx after a time Tx determined by time constant C-R.

Therefore, a time tI after a predetermined time T which is sufficiently shorter than the above time Tx from the time to, a time t2 after the above time T1 from a time L1, and the above time T from the time t2,
The voltage V1 between both ends of the measured object at time t3 after passing through
V2 and V3 are expressed as, and from equations (1) and (2), 2V+ ■2, so I (2V.

V2). Also, since ■1 R ■2 ■1 R, it becomes ■1. However, the above is for the case where the voltage V between both ends of the measured object does not oscillate, but if the voltage V oscillates when a current is passed through the measured object because the measured object has an inductance, (1) Equation 2~(8) does not hold.

The invention of claim 1 is applicable to the case where it is clear in advance that the voltage (2) across the object to be measured does not oscillate when a current is passed through the object, and in this case, immediately after the second time t2, (5 ) is calculated, and the calculation result is output as the resistance value R of the measured object, so even if the resistance value R of the measured object is large, the resistance value R can be calculated quickly and accurately. can be measured.

The invention of claim 2 is applicable to the case where it is not clear in advance whether or not the voltage between both ends of the object to be measured will oscillate or there is a possibility that it will oscillate when a current is passed through the object, and in this case, Immediately after the third time t3, the ratio or difference between the left and right sides of equation (8) is determined, and depending on whether the ratio or difference is within a certain range, the voltage between both ends of the object to be measured oscillates. When it is determined that the voltage ■ is not oscillating, the right side of equation (5) is calculated immediately after that, and the calculation result is output as the resistance value R of the object to be measured. By this, even if the resistance value R of the object to be measured is large, it is possible to measure the resistance value R accurately in a short time, and when it is determined that the voltage ■ is oscillating, the voltage ■ The resistance value R of the object to be measured is determined from the voltage (4) across the object to be measured at a fourth time t4 after the time when is expected to reach the final value R-1.

"Example" FIG. 1 shows an example of the resistance value measuring device of the present invention.

The resistance value measuring device of this example, as shown as a device 10 in the same figure, has a constant current I
1, a switch 12 inserted between the constant current source 11 and the object to be measured 1, and an A/D converter 1 to convert the voltage across the object to be measured 1 into digital data.
3. An amplifier 14 with a gain of 1 for impedance matching inserted between the object under test 1 and the A/D converter 13, and a switch 12 and the A/D converter 13 as described later.
It is provided with a control calculation circuit 15 that controls and performs calculations to be described later. The control arithmetic circuit 15 is specifically constituted by a microprocessor, and executes the following control and arithmetic operations according to a program as shown in FIG. However, the control calculation circuit 15 is given information in advance as to whether or not it is necessary to determine whether or not the voltage (2) is oscillating.

With the object to be measured 1 connected to the device 10, the control calculation circuit 15 first turns on the switch 12 in a process 21. As shown in Figure 2, Figure 3 or Figure 4,
The time point when the switch 12 is turned on will be referred to as time point to below.

Next, proceeding to process 22, FIG.
As shown in the figure, time t after a predetermined time T has elapsed from time to
1, by supplying the measurement signal SP to the A/D converter 13, the A/D converter 13 measures the voltage (2) across the device under test 1 at time t1. That is, the A/D converter 13 converts the voltage ■1 into digital data. Here, the time T is the resistance value of the device under test 1 when the voltage V between both ends of the device under test 1 does not oscillate as shown in FIG. 2 or 3 when a current is passed through the device under test 1. The voltage V from time to when rising as an exponential function with a time constant C−R formed by R and the input capacitor 1c at the point where the device 10 is connected to the device under test 1.
The time is set to be sufficiently short compared to the time Tx until the time tx reaches the final value R·I. Next, in process 23, measurement data of the voltage V is taken in from the A/D converter 13 and stored.

Next, proceed to process 24 to
As shown in the figure, by supplying the measurement signal SP to the A/D converter 13 at a time L2 after the above-mentioned time T1, the A/D converter 13 receives a Have the students measure the voltage ■2. That is, the voltage (2) is converted into digital data in the A/D converter 13. Next, in process 25, the measurement data of voltage 2 is taken in from the A/D converter 13 and stored.

Next, proceeding to decision 26, it is determined from the information given to the control calculation circuit 15 in advance as described above whether or not it is necessary to determine whether or not the voltage V is oscillating.
If it is clear in advance that the voltage ■ does not oscillate when a current is passed through the object to be measured l, and it is determined that this determination is not necessary, then in process 27, the voltage ■ and v2 are measured. From the data (
5) Calculate the right side of the equation and calculate the dirt as the resistance value R of the object to be measured 1.
The control calculation circuit 15 outputs the signal as a signal. Therefore, at this time, the resistance value R is accurately measured immediately after time L2.

Because it is not clear in advance whether or not the voltage ■ will oscillate when a current is applied to the object to be measured 1, or because there is a possibility that the voltage oscillates, it is determined in decision 26 whether or not the voltage oscillates. When it is determined that the above-mentioned time T is required, the process proceeds to process 28, and the measurement signal S is sent to the A/D converter 13 at time t3 after the above-mentioned time T has passed from time L2 as shown in FIG. 3 or 4.
By supplying P, the A/D converter 13 measures the voltage 3 across the device under test 1 at time L3. That is, the voltage ■3 in the A/D converter 13
is converted into digital data. Then process 29
At this point, the measurement data of voltage (3) is taken in from the A/D converter 13 and stored.

Next, proceeding to process 30, the ratio between the left side and the right side of equation (8) is calculated from the measurement data of voltages 1V2 and V3 above, and then in decision 31, the ratio is within a certain range centered around 1. As shown in Figure 3, if the voltage V is not oscillating and the left side and right side of equation (8) are equal in principle as described above, the ratio will be within the above range. When it is determined that the value is within the range, the process proceeds to step 27, where the right side of equation (5) is calculated from the measurement data of the voltages vI and v2, and this is used as the resistance value R of the object to be measured 1 in the control calculation circuit. Output from 15.

Therefore, at this time, the resistance value R is accurately measured immediately after time t3.

As shown in Fig. 4, voltage ■ is oscillating and equation (8) does not hold, so at decision 31, (8
) If it is determined that the ratio between the left side and the right side of the equation is not within the above range, then the process proceeds to step 32, and the time point at which the voltage ■ is expected to reach the final value R-1 as shown in FIG. 4 is determined. By supplying the measurement signal SP to the A/D converter 13 at a subsequent fourth time point L4, the A/D converter 1
3 to measure the voltage v4 between both ends of the device under test 1 at time L4. That is, the A/D converter 13 converts the voltage 4 into digital data.

Next, in process 33, V, /I is calculated from the measurement data of this voltage (4), and this is calculated as the resistance (I
It is output from the control calculation circuit 15 as IR. Therefore, at this time, the resistance value R is measured immediately after time t4.

In addition, in process 30, the difference between the left side and the right side of equation (8) is calculated, and in decision 31, it is determined whether or not the voltage V is oscillating by determining whether the difference is within a certain range. It may be determined.

Effects of the Invention j As described above, according to the invention of claim 1 or 2, even if the resistance value of the object to be measured is large, the resistance value can be measured accurately in a short time.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a state in which an object to be measured is connected to an example of the resistance value measuring device of the present invention, FIGS. 2, 3, and 4 are time charts for explaining its operation, and FIG. The figure is a flowchart showing an example of a control and calculation program executed by the control calculation circuit, FIG. 6 is a diagram showing a state in which an object to be measured is connected to an example of a conventional resistance value measuring device, and FIG. , is a time chart for explaining its operation.

Claims (2)

[Claims] (1) A constant current source that flows a constant current I through the object to be measured whose resistance value R is to be measured; an A/D converter that converts the voltage across the object to digital data; A first point in time after a predetermined time sufficiently shorter than the time required for the voltage between both ends of the object to be measured to reach the final value R·I from the time when the current starts flowing from the constant current source, and this first point in time. Voltages V_1 and V_ across the object under test at a second point in time after the predetermined time from
2 as digital data from the A/D converter, and from that digital data V_1^2/I (2V
_1-V_2) and a control arithmetic circuit that calculates the calculated value as the resistance value R. A resistance value measuring device. (2) a constant current source that flows a constant current I through the object to be measured whose resistance value R is to be measured; an A/D converter that converts the voltage across the object to digital data; A first point in time after a predetermined time sufficiently shorter than the time required for the voltage across the object to be measured to reach the final value R·I from the time when the current starts flowing from the constant current source, this first point in time; The voltages V_1, V_2, and V_3 across the object to be measured at a second time point after the predetermined time period and a third time point after the predetermined time period from the second time point are converted into digital data from the A/D converter. and from that digital data (V_2-V_
1) /V_1 and (V_3-V_2)/(V_2-V_1
) is calculated, and when this ratio or difference is within a certain range, V_1^2 is calculated from the above digital data.
/I(2V_1-V_2) and outputs it as the resistance value R. If the ratio or difference is not within the certain range, the voltage across the object to be measured becomes the final value R. Determining the voltage V_4 across the object to be measured at a fourth point after the time when it is expected to reach I as digital data from the A/D converter,
A control calculation circuit that calculates V_4/I from the digital data and outputs it as the resistance value R. A resistance value measuring device.