JP2008157750A - Resistance meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resistance meter for preventing trouble due to contact failure with a measuring object. <P>SOLUTION: The insulation resistance meter 1 includes a power supply part 2 for supplying a test voltage Vt to the measuring object 100 and formed so that it can measure the resistance value of the object 100. The resistance meter 1 includes a detection part 5 for detecting variation in an electric current value of an electric current It flowing through the object 100 to output a voltage signal Vb showing the size of the variation while the test voltage Vt is supplied thereto, a sound output part 7, and a processing part 6 causing the output part 7 to output a sound for a prescribed and definite length of time when the size of the variation in the current value of the electric current It shown by a detection signal Vb first reaches a first reference value previously stipulated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ohmmeter that measures a resistance value of a measurement object.

As this type of resistance meter, an insulation resistance meter disclosed by the applicant in Japanese Patent Application Laid-Open No. 2000-214194 is known. In this insulation resistance meter, the CPU measures the resistance value of the measured electrical device based on, for example, the current value and supply voltage input via the probe, and the measured resistance value of the measured electrical device and the set reference value When the resistance value is smaller than the reference value, the measured electrical device is determined to be defective and the buzzer is sounded. Therefore, in this insulation resistance meter, by setting a reference value in advance, it is possible to notify the state of a non-defective product or a defective product of the electric device to be measured.
JP 2000-214194 A (page 1-5, FIG. 1)

  However, the above insulation resistance meter has the following problems to be improved. That is, in this insulation resistance meter, the state of the non-defective product or the defective product of the measured electrical device is notified by comparing the measured resistance value of the measured electrical device with the reference value. In this case, when a poor contact between the electric device to be measured and the probe occurs, the measured resistance value becomes infinite and exceeds the reference value, so the buzzer does not sound. For this reason, in this insulation resistance meter, even if the electric device to be measured is a defective product, there is a possibility that it is not notified that the electric device to be measured is a defective product when a contact failure occurs. Therefore, it is preferable to improve inconvenience due to poor contact between the electric device to be measured and the probe.

  The present invention has been made in view of such a problem to be improved, and a main object of the present invention is to provide an ohmmeter that can avoid inconvenience due to poor contact with a measurement object.

  In order to achieve the above object, the ohmmeter according to claim 1 includes a power supply unit that supplies a test voltage to the measurement object, and is configured to be able to measure a resistance value of the measurement object, A detection unit that detects a change in the current value of the current flowing through the measurement object when a test voltage is supplied and outputs a detection signal indicating the magnitude of the change, a sound output unit, and the detection signal A processing unit that causes the sound output unit to output a sound for a predetermined time length when the magnitude of the indicated fluctuation first reaches a first reference value that is defined in advance.

  The ohmmeter according to claim 2 is the ohmmeter according to claim 1, wherein the processing unit has a second reference value whose magnitude of the fluctuation is less than or equal to the first reference value when the predetermined time elapses. When exceeding, the sound output unit is caused to output the sound until the magnitude of the fluctuation becomes equal to or less than the second reference value.

  The ohmmeter according to claim 3 is the ohmmeter according to claim 2, wherein the sound output unit changes the frequency according to the elapsed time of the output of the sound and outputs the sound.

  The ohmmeter according to claim 4 is the ohmmeter according to any one of claims 1 to 3, wherein the first reference value and the second reference value are defined to be the same value.

  The ohmmeter according to claim 5 is the ohmmeter according to any one of claims 1 to 4, wherein the detection unit detects the current flowing through the measurement object and indicates a current value of the current. A current detection circuit that outputs a signal; and a differentiation circuit that generates the detection signal by differentiating the signal output from the current detection circuit with respect to time.

  The resistance meter according to claim 1, wherein the processing unit outputs sound to the sound output unit at a constant predetermined time length when the magnitude of the fluctuation of the current value indicated by the detection signal first reaches the first reference value. Let In this case, for example, when supplying a test voltage to the measurement object via the probe and detecting a current flowing through the measurement object, when the measurement object and the probe are in normal contact, a high-resistance measurement object Even if it is a body (for example, when the object to be measured is a non-defective product when used as an insulation resistance meter), a charging current for charging its internal capacity flows instantaneously. For this reason, the magnitude of the fluctuation of the current value indicated by the detection signal changes only for a very short time. On the other hand, when a contact failure occurs between the measurement object and the probe, no current flows through the measurement object, so that the magnitude of the fluctuation of the current value indicated by the detection signal does not change. Therefore, according to this resistance meter, when the first reference value is set so that the fluctuation of the current value caused by the charging current can be detected, the measurement object and the probe are in normal contact. For example, sound can be output for a predetermined length of time, so that it is possible to reliably recognize a contact failure with a measurement object, and thus it is possible to reliably avoid inconveniences caused by the contact failure.

  3. The resistance meter according to claim 2, wherein when the magnitude of the fluctuation of the current value exceeds the second reference value when the predetermined time elapses, the processing section has a time when the magnitude of the fluctuation becomes equal to or less than the second reference value. Sound is output to the sound output unit. In this case, the lower the resistance value of the measurement object (for example, the defective product when used as an insulation resistance meter), the larger the current value of the current flows through the measurement object in addition to the charging current. The time until the magnitude of the fluctuation of the current value of the generated current reaches the second reference value, that is, the time until the value of the flowing current becomes stable becomes longer. Therefore, according to this resistance meter, the lower the resistance value, the longer the length of the sound is output, and as a result, when used as an insulation resistance meter, the difference in the length of the sound is discerned, so that the measurement object It is possible to reliably and easily grasp the degree of defects.

  In the ohmmeter according to claim 3, the sound output unit changes the frequency according to the elapsed time of the sound output and outputs the sound. In this case, the lower the resistance value, the longer the sound output time. Therefore, the lower the resistance value of the measurement object (for example, the poorer the product when used as an insulation resistance meter), the higher the frequency (or the lower the resistance value). The sound output section outputs from the frequency) to the low frequency (or high frequency) sound. Therefore, according to this ohmmeter, it is possible to more reliably and easily grasp the degree of failure of the measurement object by distinguishing changes in the sound frequency.

  According to the resistance meter of the fourth aspect, the first reference value and the second reference value are defined to be the same value, so that the apparatus can be configured simply.

  6. The resistance meter according to claim 5, wherein the differentiating circuit provided in the detection unit differentiates the signal indicating the current value output from the current detecting circuit with respect to time, thereby indicating the magnitude of fluctuation of the current value. Is generated. In this case, the value obtained by differentiating the signal indicating the current value is a value indicating the rate of change of the current value. Therefore, according to this ohmmeter, since the fluctuation | variation of an electric current value can be detected reliably, the contact failure with a measuring object can be recognized still more reliably.

  The best mode of an ohmmeter according to the present invention will be described below with reference to the accompanying drawings.

  First, the configuration of an insulation resistance meter 1 to which the resistance meter according to the present invention is applied will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the insulation resistance meter 1 includes probes P 1 and P 2, a power supply unit 2, a meter 4, a detection unit 5, a processing unit 6, and a sound output unit 7, and calculates an insulation resistance value R of the measurement object 100. It is configured to be measurable. In this case, the measurement object 100 generally has an internal capacitance 102 in addition to the internal resistance 101.

  The probes P1 and P2 are probes for supplying a DC test voltage (for example, several kV) Vt to be supplied (applied) to the measurement object 100 and detecting a current It described later, and measuring the insulation resistance value R. In this case, the measurement object 100 is brought into contact with both ends. The power supply unit 2 generates and outputs a test voltage Vt. The meter 4 is, for example, an analog meter, and displays the measured insulation resistance value R of the measurement object 100 by the deflection angle of the pointer. The detection unit 5 includes a current detection circuit 51 and a differentiation circuit 52. The current detection circuit 51 includes a detection resistor (not shown), detects the current It flowing through the measurement object 100 when the test voltage Vt is supplied, and outputs a voltage signal Va indicating the current value of the current It. To do. Specifically, the current detection circuit 51 outputs a voltage generated at both ends of the detection resistor as the voltage signal Va when the current It flows. In this case, since the resistance value of the detection resistor is constant, the voltage signal Va indicates a voltage value that is proportional to the current value of the current It flowing through the measurement object 100. The differentiating circuit 52 generates and outputs a voltage signal Vb (corresponding to the detection signal of the present invention) by differentiating the voltage signal Va output from the current detection circuit 51 with time. In this case, the voltage signal Vb is generated by differentiating the voltage signal Va indicating the current value of the current It with time, and indicates the magnitude of fluctuation of the current value of the current It with respect to time.

  The processing unit 6 includes a comparison circuit 61, a timer circuit 62, and an addition circuit 63. The comparison circuit 61 includes, for example, a comparator (not shown), and the voltage value of the voltage signal Vb is equal to or higher than a reference voltage value Vs (corresponding to the first reference value and the second reference value in the present invention). Sometimes a high voltage signal S1 is output, and when the voltage value of the voltage signal Vb is less than the reference voltage value Vs, a low voltage signal S1 is output. In this case, the reference voltage value Vs is set to a voltage value capable of detecting a change in the voltage signal Va when a charging current Ic described later flows. The timer circuit 62 outputs the high voltage signal S2 for a certain time T1 (predetermined time in the present invention) when the signal S1 changes from the low voltage to the high voltage. The adder circuit 63 is an OR circuit, and outputs a high voltage signal S3 when at least one of the signal S1 and the signal S2 is a high voltage, and outputs a low voltage signal S3 when both are low voltages. To do.

  The sound output unit 7 includes, for example, an oscillation circuit 71, an amplification circuit 72, and a speaker 73, and outputs a sound according to a signal S3 output from the processing unit 6. For example, as shown in FIG. 5, the oscillation circuit 71 is defined at the same time as the time T1 of the signal S2 output from the timer circuit 62 when the signal S3 output from the processing unit 6 is at a high voltage. An output signal So having a constant frequency F1 is output until the time Ta elapses, and after the time Ta elapses, an output signal So whose frequency decreases from the frequency F1 at a constant change rate according to the elapsed time T is output. To do. The time Ta when the output signal So of the frequency F1 is output from the oscillation circuit 71 and the time T1 of the signal S2 can be made different. The amplifier circuit 72 amplifies the output signal So output from the oscillation circuit 71 and outputs the amplified signal to the speaker 73. The speaker 73 outputs sound based on the output signal So.

  Next, the usage method of the insulation resistance meter 1 is demonstrated with reference to drawings.

  First, as shown in FIG. 1, the probes P <b> 1 and P <b> 2 are connected to the measurement object 100. Next, the voltage value setting button of the operation unit (not shown) is operated to set the voltage value of the test voltage Vt supplied to the measurement object 100, and then the start button is operated.

  Thereby, the power supply part 2 produces | generates the test voltage Vt of the set voltage value, and supplies it to the measuring object body 100 via the probes P1 and P2. In this case, when the contact between the probes P1 and P2 and the measurement object 100 is normal and both are electrically connected, the insulation resistance value R of the measurement object 100 (resistance value of the internal resistance 101). Regardless of the size, the charging current Ic for charging the internal capacitor 102 flows in a very short time. Therefore, the current detection circuit 51 detects the charging current Ic and outputs it as the voltage signal Va. Here, when the insulation resistance value R is large (when the measuring object 100 is a non-defective product), since the current Ir hardly flows through the internal resistance 101, the voltage signal Va is, for example, as shown in FIG. The voltage value increases gradually and then gradually decreases. At this time, the differentiating circuit 52 differentiates the voltage signal Va and outputs a voltage signal Vb. In this case, when the insulation resistance value R is large, the differentiating circuit 52 outputs a voltage signal Vb in which the time during which the reference voltage value Vs or more is shorter than the time T1 is shown in FIG. Next, the comparison circuit 61 compares the voltage value of the voltage signal Vb with the reference voltage value Vs, and as shown in FIG. 5C, the voltage signal Vb is over the reference voltage value Vs. A signal S1 that is a high voltage is output. Subsequently, the timer circuit 62 outputs a signal S2 that becomes a high voltage for a time T1 from the time when the signal S1 changes from a low voltage to a high voltage.

  Next, the adder circuit 63 adds the signal S1 and the signal S2, and the signal that becomes the high voltage over a period from when the signal S1 becomes the high voltage until both the signals S1 and S2 become the low voltage. S3 is output. In this case, since both signals S1 and S2 become low voltage after the elapse of time T1, as shown in FIG. 2 (d), the adder circuit 63 outputs a signal S3 that becomes high voltage only during time T1. Output. Next, the oscillation circuit 71 of the sound output unit 7 outputs the output signal So of the frequency F1 over the time T1. At this time, the amplifier circuit 72 amplifies the output signal So and outputs a sound having the frequency F1 during the period of time T1. As a result, when a sound is output from the speaker 73, no contact failure occurs between the probes P1 and P2 and the measurement object 100, and the measurement object is based on the length of the sound output time. It can be determined that 100 is a non-defective product. At this time, the charging current Ic mainly flows through the meter 4 for a very short time. Therefore, for example, as shown in FIG. 6A, the pointer of the meter 4 is instantaneously shaken toward the position of the scale having the low resistance value. Further, for example, a beeping sound is output from the speaker 71 over time T1. Next, the pointer of the meter 4 swings back toward the position of the high resistance value scale, and finally stops in a state where the scale of the infinite resistance value is shown.

  On the other hand, when there is no contact failure between the probes P1 and P2 and the measurement object 100 and the insulation resistance value R is slightly small (the insulation resistance value R is medium (the measurement object 100 is somewhat defective)). 3), the current Ir having a small current value flows through the internal resistor 101 in addition to the charging current Ic for charging the internal capacitor 102, so that the voltage signal Va is, for example, as shown in FIG. After the value rises momentarily, it stabilizes at a slightly lower voltage value. Therefore, the differentiating circuit 52 outputs a voltage signal Vb in which the time during which the reference voltage value Vs is equal to or greater than the time T1 is longer than the time T1, as shown in FIG. Next, as shown in FIG. 3C, the comparison circuit 61 outputs a signal S1 that becomes a high voltage over a period in which the voltage signal Vb is equal to or higher than the reference voltage value Vs. Subsequently, the timer circuit 62 outputs a signal S2 that becomes a high voltage for a time T1 from the time when the signal S1 changes from a low voltage to a high voltage.

  Next, the adder circuit 63 adds the signal S1 and the signal S2, and the signal that becomes the high voltage over a period from when the signal S1 becomes the high voltage until both the signals S1 and S2 become the low voltage. S3 is output. That is, as shown in FIG. 3D, the adder circuit 63 adds a time T1 and a time T2 that is a sum of the time Te1 from when the time T1 elapses until both signals S1 and S2 become low voltages. A signal S3 that becomes a high voltage is output. Next, the oscillation circuit 71 outputs the output signal So over time T2. In this case, the oscillation circuit 71 outputs the output signal So of the frequency F1 over the time T1 (time Ta), and after the time T1, the frequency F gradually increases according to the length of the elapsed time T thereafter. The output signal So that decreases to the time Te1 is output over the time Te1. In this case, as shown in FIG. 5, the final frequency F of the output signal So at the time when the time T2 has elapsed is a frequency F2 that is a frequency corresponding to the time T2 (corresponding to the time Te1). At this time, after the amplification circuit 72 amplifies the output signal So and outputs the sound of the frequency F1 during the period of time T1, the sound of the frequency F gradually decreasing to the frequency F2 during the period of time Te1. Output. As a result, by outputting sound from the speaker 73, it can be determined that there is no contact failure between the probes P1, P2 and the measurement object 100. Furthermore, when the sound output time is time T2, and the frequency F changes to the frequency F2, the insulation resistance value R of the measuring object 100 is determined based on the length of the sound output time and the frequency change. Can be determined to be a somewhat defective product. At this time, a current Ir having a small current value flows through the meter 4 in addition to the charging current Ic. Therefore, the pointer of the meter 4 stops in a state where a scale having a slightly smaller resistance value is shown after instantaneously swinging toward the position of the scale having a low resistance value.

  Further, when no contact failure occurs between the probes P1 and P2 and the measurement object 100 and the insulation resistance value R is small (when the measurement object 100 is a defective product), the charging for charging the internal capacitor 102 is performed. In addition to the current Ic, a current Ir having a large current value flows through the internal resistor 101, so that the voltage signal Va further increases after the voltage value instantaneously increases, for example, as shown in FIG. Stable at high voltage values. Therefore, the differentiating circuit 52 outputs a voltage signal Vb in which the time during which the reference voltage value Vs is equal to or greater than the time T2 is longer than the time T2, as shown in FIG. Next, as shown in FIG. 3C, the comparison circuit 61 outputs a signal S1 that becomes a high voltage over a period in which the voltage signal Vb is equal to or higher than the reference voltage value Vs. Subsequently, the timer circuit 62 outputs a signal S2 that becomes a high voltage for a time T1 from the time when the signal S1 changes from a low voltage to a high voltage.

  Next, the adder circuit 63 adds the signal S1 and the signal S2, and the signal that becomes the high voltage over a period from when the signal S1 becomes the high voltage until both the signals S1 and S2 become the low voltage. S3 is output. That is, as shown in FIG. 4D, the adder circuit 63 adds a time T1 and a time T3 obtained by adding up the time Te2 from when the time T1 elapses until both signals S1 and S2 become low voltage. A signal S3 that becomes a high voltage is output. Next, the oscillation circuit 71 outputs the output signal So over time T3. In this case, the oscillation circuit 71 outputs the output signal So of the frequency F1 over the time T1 (time Ta), and after the time T1, the frequency F gradually increases according to the length of the elapsed time T thereafter. The output signal So that decreases to the time Te2 is output over the time Te2. In this case, as shown in FIG. 5, the final frequency F of the output signal So at the time when the time T3 has elapsed is a frequency F3 that is a frequency corresponding to the time T3 (corresponding to the time Te2). At this time, after the amplification circuit 72 amplifies the output signal So and outputs the sound of the frequency F1 during the period of time T1, the sound of the frequency F gradually decreasing to the frequency F3 during the period of time Te2. Output. As a result, by outputting sound from the speaker 73, it can be determined that there is no contact failure between the probes P1, P2 and the measurement object 100. Furthermore, the output time of the sound is time T3, and the frequency F changes to the frequency F3 lower than the frequency F2, so that the measurement object 100 is changed based on the length of the output time of the sound and the change of the frequency. Since the insulation resistance value R is small, it can be determined that the product is defective. At this time, a large current Ir other than the charging current Ic flows through the meter 4. Therefore, for example, as shown in FIG. 6B, the pointer of the meter 4 swings toward the position of the scale having a lower resistance value, and swings to the position of the scale having a smaller resistance value. Further, the speaker 71 outputs a beeping sound whose frequency gradually decreases, for example, over time T3. Subsequently, the pointer of the meter 4 stops in a state where the scale of the small resistance value is shown.

  On the other hand, when a contact failure occurs between the probes P1 and P2 and the measurement target object 100, the measurement target object 100 regardless of the insulation resistance value R (resistance value of the internal resistance 101) of the measurement target object 100. Does not flow current It. For this reason, the current detection circuit 51 outputs the voltage signal Va indicating that the current value of the current It is zero amperes. As a result, since the voltage signal Va does not change, the voltage value of the voltage signal Vb indicates zero volts. Therefore, since the voltage value of the voltage signal Vb does not become equal to or higher than the reference voltage value Vs, the processing unit 6 does not generate the output signal So. For this reason, since no sound is output from the speaker 73, it can be determined that a contact failure has occurred between the probes P <b> 1 and P <b> 2 and the measurement object 100.

  As described above, according to the insulation resistance meter 1, when the magnitude of the fluctuation of the current value of the current It indicated by the voltage signal Vb first reaches the reference voltage value Vs, the sound output unit 7 over time T1. As a result of providing the processing unit 6 for outputting sound, the sound can be output over time T1 only when the probes P1, P2 and the measurement object 100 are in normal contact with each other. As a result of being able to reliably recognize the contact failure with the object 100, it is possible to reliably avoid inconveniences caused by the contact failure.

  Further, according to this insulation resistance meter, when the processing unit 6 determines that the voltage value of the voltage signal Vb exceeds the reference voltage value Vs when the time T1 has elapsed, the voltage value of the voltage signal Vb is less than or equal to the reference voltage value Vs. By outputting the sound to the sound output unit 7 until a certain point in time, the lower the insulation resistance value R, the longer the sound length is output. As a result, the object to be measured is identified by listening to the difference in sound length. The degree of 100 defects can be grasped reliably and easily.

  Further, according to the insulation resistance meter 1, the sound output unit 7 outputs the sound by changing the frequency F according to the elapsed time T of the sound output, so that the change in the sound frequency F is recognized. The degree of failure of the object 100 can be grasped more reliably and easily.

  Further, according to the insulation resistance meter 1, the detection unit 5 includes the differentiation circuit 52 that generates the voltage signal Vb by differentiating the voltage signal Va output from the current detection circuit 51 with respect to time. Therefore, the contact failure with the measuring object 100 can be recognized more reliably.

  In addition, this invention is not limited to said structure. For example, although the example in which the first reference value and the second reference value are defined as the same value in the present invention has been described, the first reference value and the second reference value can be defined as different values. For example, as shown in FIG. 4, a reference voltage value Vs2 (corresponding to the second reference value in the present invention) is defined, and the comparison circuit 61 causes the voltage signal Vb as shown by a broken line in FIG. The output of the high voltage signal S1 is started when the voltage value of is higher than the reference voltage value Vs, and the output of the high voltage signal S1 is stopped when the voltage value of the voltage signal Vb becomes equal to or lower than the reference voltage value Vs2. As a result, the adding circuit 63 adds the signal S1 and the signal S2, and as shown by the broken line in FIG. 4D, both the signals S1 and S2 are low voltage from the time T1 and the time T1 has elapsed. A signal S3 that is at a high voltage is output over a time T3 obtained by adding up the time Te2 until. Even in this configuration, the above-described effects can be similarly achieved. However, by defining the first reference value and the second reference value as the same value, the insulation ohmmeter 1 can be easily configured.

  In addition, the sound output unit according to the present invention can be configured using an acoustic element that outputs a sound such as a buzzer. In this configuration, the acoustic element in the sound output unit is caused to ring using the signal S3 output from the adder circuit 63 as a drive signal. Even in this configuration, the state of the non-defective / defective product of the measurement object 100 can be easily determined based on the difference in the length of the output sound. Further, the present invention can be applied to an ohmmeter configured to display a measurement value with a digital meter instead of the analog meter 4. In this configuration, the difference value of the current values for the continuously measured current It is used as a detection signal, and when the difference value first reaches the first reference value, a sound is output to the sound output unit 7 over time T1. When the difference value exceeds the second reference value at the elapse of time T1, the sound output unit 7 outputs a sound until the difference value becomes equal to or less than the second reference value. The same effect can be achieved. Furthermore, the present invention is applicable not only to the insulation resistance meter 1 but also to a resistance meter such as a multimeter.

1 is a block diagram showing a configuration of an insulation resistance meter 1. FIG. FIG. 4 is a signal waveform diagram of a voltage signal Va, a voltage signal Vb, a signal S1, and signals S2 and S3 when the insulation resistance value R of the measurement object 100 is large. It is a signal waveform diagram of the voltage signal Va, the voltage signal Vb, the signal S1, and the signal S3 when the insulation resistance value R of the measurement object 100 is medium. It is a signal waveform diagram of voltage signal Va, voltage signal Vb, signal S1, and signal S3 when the insulation resistance value R of the measurement object 100 is small. FIG. 6 is a diagram illustrating a relationship between a frequency F of an output signal So generated by an oscillation circuit 71 and an elapsed time T. It is explanatory drawing which shows the relationship between the movement of the pointer | guide of the meter 4, and the output of a sound when the insulation resistance value R of the measuring object 100 is large and small.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation resistance meter 2 Power supply part 5 Detection part 6 Processing part 7 Sound output part 51 Current detection circuit 52 Differentiation circuit 100 Measurement object F Frequency It Current So Output signal T1 Time Va, Vb Voltage signal Vs Reference voltage value Vs2 Reference voltage value Vt test voltage

Claims (5)

A resistance meter comprising a power supply for supplying a test voltage to a measurement object, and configured to be able to measure the resistance value of the measurement object,
A detection unit that detects a change in the current value of the current flowing through the measurement object when the test voltage is supplied and outputs a detection signal indicating the magnitude of the change, a sound output unit, and the detection signal And a processing unit that causes the sound output unit to output a sound for a predetermined length of time when the magnitude of the variation indicated by is first reached a first reference value defined in advance.   When the magnitude of the fluctuation exceeds a second reference value that is less than or equal to the first reference value at the elapse of the predetermined time, the processing unit continues until the magnitude of the fluctuation becomes less than or equal to the second reference value. The resistance meter according to claim 1, wherein the sound output unit outputs the sound.   The resistance meter according to claim 2, wherein the sound output unit outputs the sound by changing a frequency according to an elapsed time of the output of the sound.   The ohmmeter according to claim 1, wherein the first reference value and the second reference value are defined to be the same value.   The detection unit detects the current flowing through the measurement object and outputs a signal indicating a current value of the current, and differentiates the signal output from the current detection circuit by time. The ohmmeter according to claim 1, further comprising a differentiating circuit that generates the detection signal.

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