JP2010210459A - Resistance measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely detect only a rapid variation with time of voltage caused by a contact failure of a probe. <P>SOLUTION: A resistance measuring device includes: a current supply part 5 for supplying measurement current I1 to a measurement target 2 through current supply probes 3a and 3b; a voltage measurement part 6 for measuring voltage (input voltage) V2 input through voltage detection probes 4a and 4b connected with both ends of the measurement target 2; and a processing part 8 for integrating voltage values of the voltage V2 over a predefined integration section and also calculating an average voltage value of the voltage V2 over the integration section based on an integral value obtained by the integration to calculate resistance R of the measurement target 2, based on the average voltage value and a current value of the measurement current I1. The processing part 8 calculates a differential value B of the voltage value of the voltage V2 in the integration section per unit time, also compares it with a predetermined reference value A, and outputs the comparison result. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a resistance measuring apparatus configured to detect a contact failure between a current supply probe and a voltage detection probe that are brought into contact with a measurement object.

  As this type of resistance measuring device, a resistance measuring device disclosed in Patent Document 1 below is known. This resistance measuring apparatus includes time-division means for taking time-division by taking in time a voltage generated at both ends of the resistor based on a constant current supplied from a DC current source or a voltage proportional to the voltage, and time-division. Minimum value holding means for holding the minimum value of each voltage, maximum value holding means for holding the maximum value of each time-divided voltage, and minimum and maximum values held in both holding means after a predetermined measurement cycle Difference value calculating means for calculating a difference value between the two and an invalidity determining means for determining that the measurement is invalid if the difference value is larger than a predetermined reference value.

  In this resistance measurement, between the probe used to supply a constant current to the resistor and both ends of the resistor, and between the probe used to measure the voltage generated across the resistor and both ends of the resistor. When a contact failure occurs in at least one of the resistors, the time-dependent fluctuation of the voltage generated across the resistance to be measured increases, so that the difference value between the maximum value and the minimum value of the changing voltage also increases. For this reason, in this resistance measurement device, when this difference value becomes larger than the reference value, it is determined that a contact failure has occurred in the probe, and a contact failure occurring in the probe is detected with a very high probability. It is possible to do.

JP-A-3-2311162 (page 3-4, FIG. 1)

  However, the resistance measuring apparatus has the following problems to be solved. That is, in this type of resistance measuring device, hum noise of a commercial power supply may leak into the voltage across the resistance being measured. Since this hum noise is periodic, it can be easily and reliably canceled by integrating the time-division voltage over a section having the same length as the hum noise period, for example. However, the maximum value and the minimum value of the voltage generated at both ends of the resistance measured in the resistance measuring apparatus or the voltage proportional to the voltage, and the difference value thereof vary under the influence of hum noise. For this reason, the resistance measuring device described above not only has a rapid temporal variation in voltage due to poor contact of the probe, but also the periodicity of the voltage due to leakage of hum noise that can be easily canceled in this way. There is a problem to be solved in which it is erroneously determined that the measurement is invalid even if it varies over time.

  The present invention has been made to solve such a problem, and a main object of the present invention is to provide a resistance measuring device that can reliably detect only a rapid temporal change in voltage due to poor contact of a probe.

  In order to achieve the above object, the resistance measuring device according to claim 1 is a current supply unit that supplies a constant DC current to a measurement object via a current supply probe, and a pair of voltages connected to both ends of the measurement object. A voltage measuring unit for measuring an input voltage input via the detection probe; and integrating the voltage value of the input voltage over a predetermined integration interval and based on the integration value obtained by the integration A processing unit that calculates an average voltage value of the input voltage and calculates a resistance of the measurement object based on the average voltage value and a current value of the DC constant current, and the processing unit includes: In the integration interval, the differential value for the voltage value of the input voltage is calculated for each unit time and compared with a reference value defined in advance, and the comparison result is output.

  In the resistance measurement device according to claim 1, the processing unit integrates the voltage value of the input voltage measured by the voltage measurement unit over a predetermined integration interval, and based on the integration value, the average voltage in the integration interval A value is calculated, and a process of calculating the resistance of the measurement object based on the calculated average voltage value and the current value of the DC constant current is executed. In addition, the processing unit executes a process of calculating a differential value for the measured input voltage for each unit time and comparing it with a predetermined reference value in the integration interval, and outputs a result of the comparison. In this case, the rapid change in the measured input voltage over time is caused by a contact failure between at least one of each current supply probe and each voltage detection probe and the measurement object. Conceivable.

  Therefore, according to this resistance measurement device, based on the comparison result output from the processing unit, only a rapid temporal change due to the contact failure of each probe with respect to the input voltage measured by the voltage measurement unit, As a result of reliable detection without being affected by hum noise, it is possible to reliably prevent problems such as erroneously recognizing resistance values that include errors beyond tolerance due to poor contact as measured values. can do.

1 is a configuration diagram of a resistance measuring device 1. FIG. 6 is a waveform diagram of a voltage V2 detected by a voltage detection unit 6. FIG. It is a flowchart of a resistance measurement process.

  Hereinafter, with reference to an accompanying drawing, an embodiment of resistance measuring device 1 concerning the present invention is described.

  First, the configuration of the resistance measuring apparatus 1 will be described with reference to the drawings.

  As shown in FIG. 1, the resistance measuring device 1 is a device that measures the resistance of a measurement object 2 (in this example, a resistance value R), and includes a pair of current supply probes 3 a and 3 b and a pair of voltage detections. Probes 4a and 4b, a current supply unit 5, a voltage detection unit 6, an A / D conversion unit 7, a processing unit 8, a storage unit 9, and an output unit 10 are provided.

  One current supply probe 3 a of the pair of current supply probes 3 a and 3 b is connected to the current supply unit 5 and brought into contact with one end 2 a of the measurement object 2 as shown in FIG. 1. On the other hand, the other current supply probe 3 b is connected to the ground and brought into contact with the other end 2 b of the measurement object 2. The pair of voltage detection probes 4a and 4b are respectively connected to the input terminals of the voltage detection unit 6, and one of the voltage detection probes 4a is brought into contact with one end 2a of the measurement object 2, and the other The voltage detection probe 4 b is brought into contact with the other end 2 b of the measurement object 2.

  The current supply unit 5 is configured by a constant current source (DC constant current source) as an example, and a measurement current (DC constant current) I1 having a predetermined current value is supplied to the measurement object 2 via the current supply probe 3a. Supply to one end 2a. The measurement current I1 supplied to the measurement object 2 flows out to the ground via the current supply probe 3b that is in contact with the other end 2b of the measurement object 2. The current supply unit 5 of this example maintains the current value of the measurement current I1 at a predetermined current value by performing feedback control on the measurement current I1 while detecting the current value of the measurement current I1. For this reason, even if the contact resistance between each end 2a, 2b of the measuring object 2 and each current supply probe 3a, 3b fluctuates, the speed within a range in which feedback control by the current supply unit 5 can be responded. In the case of fluctuations (for example, the speed at which the hum noise period (50 Hz to 60 Hz) fluctuates), the measurement is performed as long as the contact state is maintained and the output voltage of the current supply unit 5 does not reach the upper limit value. The current I1 is maintained at a predetermined current value (constant current).

  As an example, the voltage detector 6 is configured by arranging an operational amplifier in the input stage, and the input impedance between the pair of input terminals is regulated to a very high value. As a result, under the condition that the measurement object 2 is not affected by noise, the current of the measurement object 2 does not flow in the voltage detection loop constituted by the voltage detection probes 4a and 4b, the voltage detection unit 6 and the measurement object 2. The voltage detection unit 6 detects the voltage (voltage between both ends) V1 generated between both ends. The voltage detector 6 amplifies a voltage (input voltage in the present invention) V2 between the pair of input terminals with a predetermined amplification factor, thereby obtaining a voltage V3 suitable for the input voltage range of the A / D converter 7. Output. In this case, as described above, even if the contact resistance between each end 2a, 2b of the measuring object 2 and each current supply probe 3a, 3b varies, the speed of the variation is about the hum noise period. When the speed is less than the fluctuation speed, the measurement current I1 flowing through the measurement object 2 is controlled to a constant current value by the current supply unit 5, and thus the voltage V1 between both ends is determined based on the resistance value of the measurement object 2. Constant voltage value. Thus, under the situation where noise (as an example, hum noise) does not leak into the voltage detection loop as described above, the voltage V2 between the pair of input terminals matches the voltage V1 between both ends, but the impedance of the voltage detection loop is Since it is extremely high, normally, the voltage V2 is in a state where a hum noise component leaks into the voltage detection loop. As a result, normally, the voltage V2 applied between the pair of input terminals of the voltage detector 6 is converted to the hum noise component (AC component of the cycle T1) in the voltage V1 (DC voltage) between both ends as shown in FIG. Is a superimposed voltage.

  The A / D converter 7 synchronizes with the sampling clock Sc (clock having a cycle shorter than an integration interval T2, which will be described later (preferably a sufficiently short cycle)), and converts the input voltage V3 into digital data D1 with a predetermined resolution. Convert and output. The processing unit 8 is constituted by a CPU, and calculates a voltage V2 input to the voltage detection unit 6 based on the digital data D1 output from the A / D conversion unit 7, and calculates the calculated voltage V2. A differential process for calculating the differential value B, an average process for removing a hum noise component, a resistance value calculation process, and the like are executed. The storage unit 9 includes a ROM and a RAM, and stores an operation program for the processing unit 8 and a reference value A for the differential value B in advance. The storage unit 9 also functions as a work memory for the processing unit 8. The output unit 10 includes a display device as an example, and displays the result of the resistance measurement process executed by the processing unit 8.

  Next, operation | movement of the resistance measuring apparatus 1 is demonstrated with reference to FIGS. In addition, one current supply probe 3a and one voltage detection probe 4a are previously brought into contact with one end 2a of the measurement object 2, and the other current supply probe 3b and the other voltage detection probe 4b are measured. It is assumed that the body 2 is in contact with the other end 2b.

  In the resistance measuring apparatus 1, in the operating state, the current supply unit 5 starts supplying the measurement current I <b> 1 to the measurement object 2. In addition, the voltage detection unit 6 starts an operation of amplifying the voltage V2 between the pair of input terminals and outputting the voltage V3 to the A / D conversion unit 7, and the A / D conversion unit 7 converts the voltage V3 to digital. The operation of converting to data D1 and outputting is started. In this state, the processing unit 8 starts executing the resistance measurement process 50 shown in FIG.

  In the resistance measurement process 50, the processing unit 8 first starts measurement (time measurement) of the integration interval T2. As an example, the integration interval T2 is defined as one cycle T1 of a hum noise component that is assumed to leak into the voltage V2, but is defined as n times the cycle T1 (n is a natural number of 2 or more). You can also. Next, the processing unit 8 executes a voltage calculation process (step 51). In this voltage calculation process, the processing unit 8 acquires the digital data D1 from the A / D conversion unit 7, and uses the acquired digital data D1 as the amplification factor of the voltage detection unit 6 and the resolution (1) of the A / D conversion unit 7. Is converted into a voltage V2 based on the voltage corresponding to the bit) and stored in the storage unit 9. The processing unit 8 executes this voltage calculation process every time digital data D1 is input from the A / D conversion unit 7.

  Subsequently, the processing unit 8 performs differentiation processing (step 52). In this differentiation process, the processing unit 8 firstly stores the voltage V2 (also referred to as “voltage V2a” for ease of understanding of the invention) stored in the storage unit 9 in the voltage calculation process executed immediately before, and this voltage. The absolute value ΔV2 (= | V2a−V2b) of the difference from the other voltage V2 calculated immediately before V2 and stored in the storage unit 9 (also referred to as “voltage V2b” for easy understanding of the invention) |) Is calculated. As an example, a configuration is employed in which the absolute value ΔV2 is calculated based on a difference between two voltages V2 that are separated by one cycle of the sampling clock Sc, but m cycles of the sampling clock Sc (m is 2). Of course, a configuration may be adopted in which the absolute value ΔV2 is calculated based on the difference between the voltages V2 separated by the above natural number). Next, the processing unit 8 divides the absolute value ΔV2 by the period of the sampling clock Sc, thereby obtaining the differential value (rate of change per unit time) B of the voltage V2 for each period of the sampling clock Sc (per unit time in the present invention). ) And stored in the storage unit 9 in correspondence with the voltage V2a.

  Next, the processing unit 8 compares the calculated differential value B with the reference value A stored in the storage unit 9 (step 53). When the differential value B is larger than the reference value A, that is, in FIG. As shown in the figure, when the voltage V2a greatly fluctuates with respect to the voltage V2b (in the figure, a state in which the voltage V2a has greatly decreased is shown as an example), that is, when the fluctuation over time is large, contact failure ( Information indicating the occurrence of a contact error is displayed on the output unit 10 (step 54). For example, when avoiding erroneous detection due to superimposition of hum noise, the reference value A is defined in advance as a value of about 0.01% of the maximum value of the digital data D1 output from the A / D conversion unit 7, for example. Has been.

  In this case, even if the contact resistance between the pair of current supply probes 3a and 3b and the respective end portions 2a and 2b of the measuring object 2 fluctuates slowly, the current supply unit 5 performs measurement by feedback control as described above. In order to keep the current value of the current I1 constant by following the change of the contact resistance, the differential value B does not become larger than the reference value A, and the pair of voltage detection probes 4a and 4b and the measurement object Even if the contact resistance between the end portions 2a and 2b of the body 2 varies to some extent, as long as the contact state is maintained, the input impedance of the voltage detection unit 6 is extremely high in the first place. Is hardly affected by the voltage value of the voltage V2 input to. Therefore, when these two points are taken into consideration, the large fluctuation of the voltage V2a with respect to the voltage V2b is caused by at least one of the pair of current supply probes 3a and 3b and each end 2a of the measurement object 2 in contact with the one. , 2b occurrence of a state in which the contact resistance suddenly fluctuates (occurrence of contact failure), and measurement in which at least one of the pair of voltage detection probes 4a, 4b is in contact with this It is considered that at least one of the occurrences of the state in which the contact resistance between each of the end portions 2a and 2b of the object 2 fluctuates rapidly (occurrence of contact failure) is shown. Therefore, when information indicating the occurrence of contact failure is displayed on the output unit 10, it is determined that contact failure has occurred in at least one of the pair of current supply probes 3a and 3b and the pair of voltage detection probes 4a and 4b. It becomes possible to do. In addition, even if the resistance value R of the measurement object 2 is calculated based on the voltage V2 calculated when the contact failure occurs in this way, the error included in the calculated resistance value R increases, so that the processing unit When the step 54 is executed, the resistance measurement process is immediately terminated.

  On the other hand, as a result of the comparison in step 53, when the differential value B is less than or equal to the reference value A, that is, when the fluctuation of the voltage V2a is small with respect to the voltage V2b, specifically, only the fluctuation caused by leakage of the hum noise component. In this case, since it is considered that no contact failure has occurred in any of the pair of current supply probes 3a and 3b and the pair of voltage detection probes 4a and 4b, the processing unit 8 performs the integration interval T2 (see FIG. Step 51 to Step 53 are repeatedly executed while determining whether or not (see 2) has ended (Step 55). As a result, the voltage V2 calculated in the integration interval T2 is sequentially stored in the storage unit 9 at the cycle of the sampling clock Sc.

  Thereafter, when it is determined in step 55 that the integration interval T2 has ended, the processing unit 8 performs an averaging process (step 56). In this averaging process, the processing unit 8 reads all the voltages V2 calculated in the integration interval T2 from the storage unit 9 and adds (integrates) them, and calculates a total value (integration value in the present invention) in the integration interval T2. The average voltage value V2av of the voltage V2 is calculated by dividing by the number of the voltages V2. In this case, as described above, since the integration interval T2 is defined to be the same length as one cycle T1 of the hum noise component, the hum noise component is canceled by this averaging process. Therefore, the average voltage value V2av of the voltage V2 indicates the voltage V1 between both ends shown in FIG.

  Finally, the processing unit 8 executes a resistance value calculation process (step 57). In this resistance value calculation process, the processing unit 8 uses the average voltage value V2av of the voltage V2 (that is, the average voltage value of the voltage V1 between both ends) as the current value (known) of the measurement current I1 supplied from the current supply unit 5. ), The resistance value R of the measuring object 2 is calculated and stored in the storage unit 9 and displayed on the output unit 10. Thereby, the resistance measurement process is completed.

  Thus, in the resistance measuring apparatus 1, the processing unit 8 calculates the differential value B for the voltage value of the voltage V2 for each unit time (one cycle of the sampling clock Sc) and the reference value A defined in advance. The comparison process is executed in the integration interval T2, and the comparison result is output to the output unit 10. Specifically, when the differential value B exceeds the reference value A, that is, when a sudden change with time in the voltage V2 is detected, the processing unit 8 causes the output unit 10 to display the occurrence of contact failure. In this case, a rapid temporal change in the voltage V2 is caused between at least one of the current supply probes 3a and 3b and the voltage detection probes 4a and 4b and the end portions 2a and 2b of the measurement object 2. This is thought to be due to the occurrence of poor contact. Therefore, according to the resistance measuring apparatus 1, only a rapid temporal change of the voltage V2 due to the contact failure of each of the probes 3a, 3b, 4a, and 4b is detected based on the information displayed on the output unit 10. As a result, it is possible to reliably detect the resistance value R including an error exceeding an allowable value due to the occurrence of a contact failure, thereby reliably preventing a problem that the resistance value R is erroneously recognized as a measured value. can do.

  In addition, this invention is not limited to said structure. For example, the processing unit 8 calculates the voltage V2 based on the digital data D1 output from the A / D conversion unit 7, and has been described above for the example in which the differential processing is executed based on the voltage V2. After the digital data D1 is temporarily stored in the storage unit 9, a differentiation process is executed based on the stored digital data D1, and a voltage V2 is calculated based on the digital data D1 in an averaging process executed thereafter. A configuration for calculating the average voltage value V2av can also be employed. Further, the example of performing resistance measurement by a four-wire system provided with a pair of current supply probes 3a and 3b and a pair of voltage detection probes 4a and 4b has been described above. However, the current supply probe 3a and the voltage detection probe 4a are shared. Of course, the current supply probe 3b and the voltage detection probe 4b can be applied to two-wire resistance measurement.

DESCRIPTION OF SYMBOLS 1 Resistance measuring apparatus 2 Measuring object 2a One edge part 2b The other edge part 3a, 3b Current supply probe 4a, 4b Voltage detection probe 5 Current supply part 6 Voltage detection part 8 Processing part 10 Output part A Reference value B Differential value T2 integration interval V2av Average voltage value I1 Measurement current

Claims (1)

A current supply unit that supplies a constant DC current to the measurement object via a current supply probe; a voltage measurement unit that measures an input voltage input via a pair of voltage detection probes connected to both ends of the measurement object; Integrating the voltage value of the input voltage over a predetermined integration interval and calculating the average voltage value of the input voltage in the integration interval based on the integration value obtained by the integration, A processing unit that calculates the resistance of the measurement object based on the value and the current value of the DC constant current,
The said process part is a resistance measuring apparatus which compares with the reference value prescribed | regulated previously, calculating the differential value about the voltage value of the said input voltage for every unit time in the said integration area, and outputs the result of the comparison.

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