JP3145506B2 - Connection test method for 4-wire resistance measurement and 4-wire resistance measurement device capable of implementing the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a technique called a four-wire resistance measurement for accurately measuring a resistance value, especially a low resistance value, and four connection cables forming an electric path for connecting the four wires. The present invention relates to cable connection confirmation for confirming whether or not a cable (simply called a cable) is securely connected to a resistance to be measured.

[0002]

2. Description of the Related Art In a four-wire resistance measurement, a current cable for flowing a known current to the same resistance is connected to both ends of a resistance to be measured, and a known constant current is supplied to the resistance to be measured via the current cable. From the current source of the measuring instrument. In this way, in order to know the potential difference between both ends of the resistance when a known current flows through the resistance to be measured, two voltage cables connected to both ends of the resistance are connected to the connection terminals of the measuring instrument. Measure the potential difference between both ends of the voltage cable as much as possible without causing current to flow, and measure the resistance value by minimizing the error due to the resistance of the voltage cable, especially to accurately measure low resistance Technology.

FIG. 8 shows a measurement circuit for actually performing this measurement.
Shown in R in FIG._x Indicates a resistance to be measured, and L₁ , L_Four But
Each is a current cable, L_Two , L_Three Is the voltage cable
It is. The measured resistance R shown_x Connect to both ends of
Is done. Measured resistance R_x Flows a known current i from the current source
Then, the switches S1 and S2 are sequentially closed, and the resistance to be measured R _x 
Voltage V across_Two And V_Three And measure This voltage cable
Le L_Two And L_Three To the connection terminal of the measuring instrument indicated by ○
Through the switches S1 and S2 through (1, 2, 3, 4).
Into the input amplifier AMP, which is a part of the internal circuit for measurement.
Because the input amplifier AMP has high impedance,
L_Two And L_Three Current does not substantially flow through the
Table L_Two , L_Three No voltage drop due to resistance
, R_x Potential difference V between terminals_Three -V_Two Measuring accurately
Can be. Since the constant current i is known, the resistance is calculated by the following equation.
The resistance value can be determined.

[0004] _{R x = (V 3 -V 2} ) / i [Ω] ( a V ₂ measured in the ON only S1 is 8, then S2 only in the ON to measure V _3.)

[0005]

In the four-wire resistance measurement, when the current cables (L ₁ and L ₄ ) are disconnected or disconnected (the disconnection also indicates disconnection), the resistance to be measured is determined. No current flows. At this time, the potential difference between the resistance terminals to be measured may be 0 V and measurement may be erroneously made as R _x = 0 [Ω]. The voltage cable (L ₂ and L ₃₎
If the cable is disconnected, the input to the internal circuit for measurement 6 in FIG. 8 becomes open and the measured value becomes unstable, but it is not known from the measured value which cable is disconnected.

[0006] The four cables L shown in FIG.
_1, L _2, L _3, well the probable one cable of the L ₄ is added to the case described as if disconnected. (1) L ₁ is broken: for measuring a current does not flow to the measured resistance R _x, the voltage between V _2, V ₃ equal zero V,
_Rx is erroneously determined to be zero Ω by the above equation. In this case, since the measured value is stable, it is not known that a trouble has occurred. (2) L ₂ is disconnected: voltage corresponding to V ₂ is Teirazu, therefore, be unstable measured value of R _x is (become unscheduled value addition to indeterminate), and the trouble has occurred can be seen . (3) L ₃ is disconnected: voltage corresponding to V ₃ is Teirazu, therefore, the measured value of R _x becomes unstable, the trouble has occurred can be seen. (4) L ₄ is broken: measuring a large no-load voltage of a state similar to the infinite resistance as measured resistance is connected, V _2, V ₃ are both overload (constant current source It means that trouble has occurred.

As described above, the cables L ₂ , L ₃ , L ₄
If only one wire is broken, the measured value is unstable or overloaded, which indicates that a trouble has occurred.
Cable L ₁ is when the disconnection is erroneously measured not know the trouble. In other words, do not know that the trouble has occurred from the disconnection of L ₁ is a measurement result.

[0008] Thus, it will be trouble when the disconnection of L ₁ is not known prior to measurement, since the measurement value and do not know before the measurement Again disconnection of L ₁ other than the cable can not be obtained, prior to the measurement in Tei' was way It is very convenient and convenient to know if there is a break in the cable and which cable is broken.

Further, since the number of disconnections of the cable is not limited to one but may be two or more, it is possible to determine which and which ones are disconnected by taking this into consideration. It is more convenient.

The present invention solves these problems and determines whether or not a cable is disconnected before calculating the value of the resistance to be measured, and determines which cable is disconnected.
It is another object of the present invention to provide a means for determining which cable is disconnected from which cable.

[0011]

Means for Solving the Problems and the Function Thereof
The present invention relates to a method using a measuring instrument capable of performing a wire resistance measurement, and the measuring instrument. The measuring instrument has a current source for flowing a known fixed current to the resistance to be measured, and the current is supplied via two current cables L ₁ and L ₄ connected to the connection terminals of the measuring instrument. The current flows through the measuring resistor _Rx . Then, two voltage cables L ₂ and L ₃ for measuring the potential difference between both ends of the resistance _{Rx to} be measured are also connected to the connection terminals of the measuring instrument to prepare for the measurement.

According to the present invention, the measurement is prepared in this way.
The connection between the two voltage cables and the reference, with reference to the potential of one of the connections to which the current cable is connected (usually grounded), to check before the measurement whether the connection of the two cables is complete. The voltage of the connection terminal of the other current cable is measured. At this time, a switch for measuring not only the voltage of the connection terminal of the two voltage cables but also the voltage of the connection terminal of the current cable which is not used as a reference by using the switches S1 and S2 in the prior art. S3 (see FIG. 1) is provided. However, this switch S3 are those provided normally by measurement using a cable of L ₁ and L ₃ by the 2-wire resistance measurements, but which has not been provided in the 4-wire.

Using the switch S3, three voltages are measured by the switches S1 and S2, and the connection of the four cables is confirmed by the voltages.

Normally, each cable has no disconnection.
Even if there is a disconnection, there is often only one disconnection. Therefore, if there is any one disconnection, it is only necessary to determine as follows based on the above three voltages.

[0015] That is, the reference side of the voltage measure the voltage at the connecting terminals of the cable it is cable L ₄ is disconnected if overloaded, not so, the cable L ₃ is disconnected if it shows a value close to 0 , then measure the voltage of the connection terminal of the current cable is not a reference side which cable L ₁ is disconnected if overload, the voltage of the connection terminal of the voltage cable not following reference side connection terminal of the current cable is not its reference side If the value of the cable L
_It is better to make the determination in the order that ₂ is disconnection.

In this case, when the connection terminal of the voltage cable other than the reference side shows a voltage close to the overload, it is determined that the measurement range is not appropriate and the constant current flowing through the resistance _Rx to be measured is determined. If the process of reducing the value of is added, it becomes more convenient for the actual measurement of _Rx .

Next, a case will be described in which the possibility that two or more disconnections are generated is not limited to one. If confirmation work is performed including this possibility, more reliable work can be performed faster.

In the four-wire resistance measurement targeted by the present invention, 2
A total of four cables, one current cable and two voltage cables, are used. If any of the cables is connected to _Rx without disconnection, any two of the four connection terminals to which these four cables are connected are used. If one is selected and it is checked whether or not power is supplied between these two terminals, power should be supplied.
If any of these four cables are broken,
There must be a combination of connection terminals that are not energized. An energization test is performed using this concept.

There are six combinations in which any two of the four cables are combined. For all of the six types, an energization test is performed to determine whether energization from one connection terminal to another connection terminal is performed. I do. Four of these six energization tests check the connection via the measured resistance _Rx , and the remaining two test the connection between the two cables through the connection terminal without passing through the _Rx. It will be. Then, if all of the six energization tests are energized, it can be determined that there is no broken cable. If one cable is disconnected, three of the six are not energized. If two cables are disconnected, only one of the six is energized. This method cannot distinguish between a case where three cables are broken and a case where all cables are broken. However, in a normal case, there is one broken wire, two broken wires, and Not only can it be distinguished when there are two or more breaks, but by analyzing the results of these six types of energization tests, as long as the resistance _Rx to be measured is not over the range that is greater than the expected value, any cable or any Which cable is disconnected can be determined.

Then, it is also possible to judge that the range is over by the six kinds of energization tests, so if one or two wires are broken, which cable or which and which cable is broken. Can be determined. In order to easily perform this, in the six continuity tests corresponding to the above six cases, if a result of non-conduction is obtained each time, a different evaluation value determined for each time is given. In other words, it is possible to obtain the convenience that it is possible to determine which cable or which and which cable is broken by the sum of all the evaluation values.

As a device for facilitating the six kinds of energization tests, a relay selection circuit incorporating a relay contact is provided inside the connection terminal of the measuring instrument, and the relay is operated to turn on and off the contact. By selecting OFF, it is possible to configure a circuit capable of performing the above six kinds of conduction tests. In other words, a relay selection circuit is incorporated between the four connection terminals of the measuring instrument and the measuring internal circuit of the measuring instrument, and the relays are selectively and sequentially operated, thereby enabling the above-mentioned 6
It is possible to configure a circuit that can automatically perform the following energization tests.

The present invention uses a 4-wire ohmmeter to measure R _x
Before calculating the resistance value of, provide a stage to automatically test whether there is a cable break, and if there is a break, indicate which cable is broken and only when there is no abnormality , _Rx . At the stage of checking whether or not these cables are disconnected, the process of determining that the resistance value of _Rx is larger than the expected range and it is better to change the measurement range is incorporated in the process of checking for the presence or absence of the above-described disconnection. As a result, the operation can be automated.

[0023]

FIG. 1 shows an embodiment of the present invention. R _x is the measured resistance, L _1, L ₄ is a current cable, L _2, L ₃ are voltage cable, ○ mark connection terminal of the measuring instrument, S1, S2, S3 are switches, AMP and A / DC is for measurement This is the internal circuit 6.
For measurement by closing in the figure's S3 as shown in Figure provided in addition to the normal S1, used in four-wire resistance measurement, S2, contacts V _2, V ₃ of the potential of the point V ₁ to the outer S3 Be able to measure with internal circuit. In a two-wire resistance measurement without using the voltage cables L ₂ and L ₃ , there is usually a switch corresponding to S3, and therefore, a resistance measurement instrument capable of two-wire and four-wire does not need to provide S3 again. In that case, the use of S3 in a four-wire system becomes a new configuration. It should be noted that the example in this figure is somewhat unsuitable because it is necessary to repeat the determination process when two or more cables are disconnected.

[0024] Using the circuit of Figure 1, according to the flowchart shown in FIG. 2, the cable L ₁ to R _x, L _2, L
_After connecting L ₃ and L ₄ to prepare for measurement, V ₁ , V ₂ ,
As it is performing judgment based on the judgment matter by measuring the V ₃ according to a predetermined order in the flowchart, if it can be determined which cable is disconnected. When it can be determined that there is no disconnection in any cable, the cable check is terminated and the resistance value of _Rx is calculated by a conventional method.

According to this flowchart, V₁ , V_Two ,
V_Three Is measured and judgment is made, R _x Is too large
The judgment that the fixed range should be changed
This can be done during the course of the decision to examine the line.

An explanation will be added to this flowchart. V
_1, V _2, V ₃ after measurement determined that V ₃ is overloaded [I], it means that large load voltage of the current source to the V ₃ L ₄ is disconnected appears. Next judgment [II] |
V ₃ |> The reference value is that if L ₃ is disconnected, V ₃ will not be close to 0 (ground potential) and will be unstable, but will be a value far from 0. A close value may be appropriately determined in advance. Next decision [III] is not whether the cable break, determination that R _x is greater than expected range (actually a constant current to flow to the R _x is too large.) Since, it is appropriate to reduce the measurement range Means that you can That is, the "proceed to the next is determined that overload" to reduce the constant current flowing through the R _x, is that again the measurement of _{V 1, V 2, V 3} . It will be certain if you re-measure all. (V ₃ may not be measured.) In this case R _x is may be displayed that too large. Since next decision [IV] is greater load voltage appearing at V ₁ when L ₁ is disconnected, is intended to see whether this voltage is pulled. The next decision [V] is supposed V ₂ is substantially equal to V ₁ unless L ₂ is disconnected, L ₂ is the V ₂ when is broken V
Since it will exhibit unstable value different from the _1, in which V ₂ is to determine the presence or absence of disconnection of L ₂ in whether substantially equal to V _1.

The flowchart of FIG. 2 can be modified.
The judgment [I] and the judgment [IV] need to be in this order, but others can be changed. Note that the judgment [III] is the judgment [I]
After is good. Further, the measurement timing of V ₁ , V ₂ , and V ₃ may be measured by the time when the data is required when making the respective judgments. Also, in the judgment [III], _Rx can be judged as overload, and when changing the measurement range, the judgment [IV] and the judgment [V] can be omitted.
V] and the determination [V], the order of determination may be more convenient.

Next, an embodiment can be performed in consideration of the possibility of disconnection of two or more of the four cables, as a matter of course.

FIG. 3 shows the embodiment. The switches S4, S5, S6, S7, S8, and S9 of the relay selection circuit 7 are used to easily perform the above-described six kinds of conduction tests between the connection terminal of the measuring instrument and the internal circuit for measurement for this embodiment. These are the contacts of the relay incorporated in the. The switches S1, S
2, S3 are provided for to perform the same function as the previous embodiment, but is intended to measure V _2, V _3, V _1, respectively, the switch S3 in particular in this embodiment the In an energization test, it is convenient to use it to determine whether or not two selected cables are energized. The switches S4 and S5 are changeover switches, and their (a and c) or (b and d) are turned on and off at the same time, respectively, and the switches (a and c) or (b and d) The relay is activated to select one of them to be on.

Using the circuit shown in FIG. 3, six patterns of energizing circuits corresponding to the six energizing tests described above are made. Then, the relay is actuated so that each of the contacts can be formed by its respective energizing circuit, and the contact is selected.

[0031] Pattern 1: cable L ₁ and L connection check current S9-S5c-L ₄ of ₄ -R _x -L ₁ -S4a-S6
Of measuring the potential of V ₁ to flow in order to see if it is or overload. L ₁ or V ₁ when either the disconnection L ₄ are the overloaded.

[0032] Pattern 2: Cable L ₁ and L ₃ of the connection check current _{S9-S5b-L 3 -R x} -L 1 -S4a-S6
Of measuring the potential of V ₁ to flow in order to see if it is or overload. L ₁ or V ₁ when either the disconnection L ₃ becomes overloaded.

[0033] Pattern 3: Cable L ₂ and L S9-S5b-L ₃ the connection check current ₃ -R _x -L ₂ -S4d-S6
Of measuring the potential of V ₁ to flow in order to see if it is or overload. V ₁ when either the disconnection of L ₂ or L ₃ becomes overloaded.

[0034] Pattern 4: Cable L ₂ and L ₄ of the connection check current _{S9-S5c-L 4 -R x} -L 2 -S4d-S6
Of measuring the potential of V ₁ to flow in order to see if it is or overload. V ₁ when either L ₂ or L ₄ is disconnected becomes overloaded.

[0035] Pattern 5: Check Connection current cables L ₁ and _{L 2 S8-S4c-L 2} -L 1 flows in the order of -S4a-S6 by measuring the potential of V _1, see if it is either overloaded . V when either L ₁ or L ₂ is a disconnection
₁ is overloaded.

[0036] Pattern 6: Check Connection current cable L ₃ and _{L 4 S9-S5c-L 4} -L 3 flows in the order of -S5a-S7 and measuring the potential of V _1, see if it is either overloaded . V when either of L ₃ or L ₄ is a disconnection
₁ is overloaded.

The potential of V ₁ is measured for the above six patterns, and it is possible to determine which cable (including a plurality) is disconnected based on the result.
Although measuring the potential of V ₁ was a One convenient means of inter-connecting jack connected to the two cable test whether current may by other means.

The current path can be obtained by selectively operating the switches of the relay selection circuit in the circuit shown in FIG. 3 using the six patterns described above, and the ON / OFF of each switch for each pattern is obtained. FIG. 4 is a diagram showing the selection, that is, the setting of the switch. Note that X in FIG.

[0039]

Indicates that either of them is on, but in that pattern (pattern 5 or pattern 6), either may be on.

V for the above six patterns₁ Potential of
Cable to check for overload or not
Are displayed in the upper row, and the judgment table is the judgment table of FIG. 5 and FIG.
The judgment states are shown in the diagrams (Part 1) and (Part 2)
did. R_x Is within the range to be measured
Time is in FIG._x Is too large than expected
Is represented in FIG. Given at the bottom of FIGS. 5 and 6.
Are the evaluation values in each pattern of the six judgments
is there. For example, L of pattern 1₁ And L_Four To check the connection
Disconnection (V₁ Overload [HI in FIGS. 6 and 7]
), The evaluation value is 32. Normal is 0
I do. The evaluation value of each pattern is
The sum of the evaluation values is shown in the rightmost column of FIGS.
Have been. Depending on the value of the evaluation, the left side of these two figures
L expressed toward₁ L_Two L_Three L _Four Cable break or
Can identify the normal state. Most three or more cables
And when R is disconnected_x Is out of range.
There is another limit.

When it is determined that _Rx is out of range, it is preferable to operate the current source to lower the constant current flowing through _Rx , that is, to change the range and repeat the energization test.

Then, the result is that everything is normal. That is, so that the sum of the evaluation value in FIG. 6 calculates the resistance value of the R _x by conventional techniques 0, will measure the value of V ₂ and V ₃ for that purpose.

[0043] While the V ₂ and V ₃ when the connection cable becomes all the normal is weighed towards the case of using the circuit of FIG. 3, S9-S5c-L ₄ a constant current at that time -R _x −
It is kept flowing in the order of L ₁ -S4a-S6. At this time, since S4c and S5a are on, first S
1 is turned on, and V ₂ is measured by the internal circuit for measurement. Then turn on the S2, off the S1, measuring the V ₃ as well. Thus, the constant current i at this time is known, and V
Since the ₂ and V ₃ is seen in the measurement, the value of R _x is calculated at.

As described above, the circuit of FIG. 3 is conveniently used for both the energization test and normal measurement. However, a modified embodiment using a comparator instead of S3 in FIG. 3 can be considered. It is shown in FIG. In this case, other parts such as a relay selection circuit have the same configuration as that of the embodiment of FIG.

[0045]

According to the present invention, it is possible to confirm before the measurement of the resistance that the cable is incomplete in the four-wire resistance measurement, so that the calculation of the resistance value can be provided with high reliability. As described above, there is no erroneous measurement, and the method of the present invention has a feature that this can be easily automated. In addition, the range of _Rx can be easily determined during the cable connection confirmation process of the present invention.
An over-detection process can be incorporated.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart for explaining operation using the circuit of FIG. 1;

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing a switch setting state of an example using the circuit of FIG. 3;

FIG. 5 is a diagram showing a determination state for determining the presence / absence of disconnection using the circuit of FIG. 3 (part 1);

FIG. 6 is a diagram showing a determination state for determining the presence / absence of disconnection using the circuit of FIG. 3 (part 2)

FIG. 7 is a circuit configuration diagram showing another embodiment replacing the circuit of FIG. 3;

FIG. 8 is a circuit configuration diagram showing an example of performing a conventional four-wire resistance measurement.

[Explanation of symbols]

1, 2, 3, 4 connection terminal 5 current source 6 internal circuit for measurement 7 relay selection circuit S1, S2, S3, S4, S5, S6, S7, S8, S
9 switches _{L 1, L 2, L 3} , L 4 Cable R _x measured resistance 8 comparator 9 micro CPU I / O port

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-288776 (JP, A) JP-A-2-259582 (JP, A) JP-A-2-259581 (JP, A) JP-A-2-259 190771 (JP, A) JP-A-2-71164 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 27/02 G01R 31/02 G01R 35/00

Claims (6)

(57) [Claims] 1. A method for confirming disconnection or disconnection of a cable, which is four connection lines to a resistance to be measured, in a four-wire resistance measurement, wherein two current cables respectively connected to both ends of the resistance to be measured. A device for measuring the voltage of the other of the connection terminals with reference to one of the connection terminals, and a device for measuring the voltage of each of the connection terminals respectively connecting the two voltage cables respectively connected to both ends of the resistance to be measured. A connection test method before performing a four-wire resistance measurement in which the connection of the four cables to the resistance to be measured is measured by measuring these three voltages. 2. One of two connection terminals for connecting two current cables connected to a resistance to be measured is connected to the resistance to be measured on the side to which the current cable based on this reference is connected. Measure the voltage at the connection terminals of the voltage cable and check whether it is overloaded, then whether it is greater than its reference value close to zero and its absolute value, Measure the voltage at the connection terminal, check if it is overloaded, and then measure the voltage at the connection terminal of the voltage cable on the other side, which is not the reference for the previous current cable. 2. The method according to claim 1, further comprising: determining whether the four cables are connected or disconnected or unconnected in an order of determining whether the voltage is sufficiently close to the terminal voltage before performing the four-wire resistance measurement. Connection line test method described above. 3. A four-wire resistance measuring instrument for performing a four-wire resistance measurement, comprising: two connection terminals for connecting two voltage cables for measuring voltages at both ends of a resistance to be measured; In addition to providing two switches for interrupting each of the two electric circuits that respectively connect the internal circuit, two current terminals that respectively connect two current terminals that respectively connect two current cables that allow a current to flow through the resistance to be measured and a current source. In order to measure the voltage of one of the two circuits that is not used as a reference for voltage measurement, the circuit to be measured and the internal circuit for measurement can be electrically connected via a switch. A four-wire resistance measuring instrument that can easily check the connection of a cable for four-wire resistance measurement. 4. A four-wire resistance measurement method comprising: connecting cables, which are four connection lines to a resistance to be measured, to a resistance to be measured, and then combining two of the four cables to obtain six types of cables. For all of the combinations, the test for whether or not the connection terminal connecting the two cables is conducted is performed six times in correspondence with the six types, and according to the results of the six tests, the covering of the four cables described above is performed. Connection test method before performing 4-wire resistance measurement to check the connection to the measured resistance. 5. In six continuity tests corresponding to all six combinations of two cables in which two of four cables are combined, if the result indicates that the connection is non-conductive each time, 5. The connection test method according to claim 4, wherein different evaluation values are given each time, and which cable is disconnected can be determined based on a total value of all the evaluation values. 6. A four-wire resistance measuring instrument for performing a four-wire resistance measurement, wherein six connection tests are performed to mechanically perform six conduction tests performed by combining two of the four cables. A relay selection circuit consisting of a combination of relay contacts that can be configured by the circuit selectively operating a switch is incorporated between the cable connection terminal of the 4-wire resistance measuring instrument and the internal circuit for measurement, and the relay is selectively selected. 4. A four-wire resistance measuring instrument according to claim 3, wherein the four-wire resistance measuring instrument is adapted to be operated.