JP5634816B2 - Resistance meter - Google Patents

Description

  The present invention relates to an ohmmeter including a meter portion on which a voltage scale and a resistance scale are written on the surface of one scale plate on which one pointer swings.

  As this type of resistance meter, the present applicant has already developed a resistance meter (insulation resistance meter) disclosed in Non-Patent Document 1 below. In addition, the applicant of the present application has already developed a ground resistance meter constituted by substantially the same circuit as this insulation resistance meter. These ohmmeters include a meter section, a pair of test leads (in the case of a ground ohmmeter, a ground side test lead and a wire side test lead), a mode switch, a major switch, a red LED, and a measurement section. The meter portion is configured by being described on an arc in which the voltage scale and the resistance scale are different over the entire range of the deflection angle of one pointer on one scale plate. The pair of test leads are connected to both ends of the measurement target whose resistance is to be measured. In the earth resistance meter, in order to measure the ground resistance of the ground electrode as a measurement object by the two-electrode method, the ground side test lead of the pair of test leads is connected to the ground electrode, and the electric wire side test lead is used for commercial use. Connected to the neutral line of the power line. Further, in these ohmmeters, when measuring a voltage (AC voltage) generated between both ends of a measurement object, a pair of test leads is connected to each end of the measurement object.

  In the insulation resistance meter, the mode changeover switch selects the operation mode of the measurement unit from a plurality of measurement voltages (for example, 125V, 250V, 500V) and supplies the insulation resistance to the measurement object. The mode is switched to one of a resistance measurement mode for measurement and a voltage measurement mode for measuring a voltage generated between both ends of the measurement target. On the other hand, in the earth resistance meter, the mode changeover switch includes an operation mode by the measurement unit, a resistance measurement mode for measuring the ground resistance while supplying a predetermined measurement voltage between the ground electrode and the neutral wire, and grounding Switch to one of the voltage measurement modes that measure the voltage between the pole and the neutral wire.

  The measure switch is operated in this resistance measurement mode for the measurement unit set in the resistance measurement mode. The red LED is used when the measurement unit is operating in resistance measurement mode (specifically, when a measurement voltage is output between a pair of test leads) and when the measurement unit is set in resistance measurement mode. When the voltage between a pair of test leads exceeds a predetermined threshold value (for example, in a ground resistance meter, the wire side test lead to be connected to the neutral wire of the commercial power line is a live wire Is lit by the measuring unit.

  The measurement unit outputs the measurement voltage between the pair of test leads when the measure switch is operated in the resistance measurement mode, and measures the current flowing in the pair of test leads in this state, Based on the measured current, the resistance of the object to be measured is measured, and the ground resistance measured on the resistance scale of the meter unit is indicated by swinging the pointer. Further, the measurement unit controls lighting of the red LED when the measure switch is operated in the resistance measurement mode (when the measurement voltage is output).

  On the other hand, when the measurement switch is not operated in the resistance measurement mode (when the measurement voltage is not output), the measurement unit measures the voltage between the pair of test leads (in the ground resistance meter, the potential of the ground side test lead) Measure the voltage on the voltage scale of the meter unit by swinging and moving the pointer, and measure the measured voltage and the above threshold value (for ground resistance meter) As an example, AC20V) is compared. As a result of this comparison, when the measured voltage is equal to or higher than the threshold value, the measurement unit controls lighting of the red LED and shifts to the lighting state.

  With the above configuration, these ohmmeters measure the resistance to be measured by supplying a measurement voltage between a pair of test leads by operating the measure switch while the resistance measurement mode is selected with the mode switch. It is possible to do. In addition, while operating the major switch, the red LED is lit to notify that a high voltage is generated between the pair of test leads, so that it is possible to prevent an electric shock. Yes. In addition, with the earth resistance meter, when the resistance measurement mode is selected with the mode selector switch, the red LED lights even when the measure switch is not operated and the wire side test lead is accidentally connected to the live wire. Then, since it is notified that the electric wire side test lead is erroneously connected, it is possible to reconnect the electric wire side test lead from the live electric wire to the neutral wire. At this time, since the voltage of the electric wire side test lead is indicated by the pointer on the voltage scale of the meter unit, it is possible to check the voltage applied to the electric wire side test lead. In these ohmmeters, the voltage to be measured can be measured by selecting a voltage measurement mode with a mode switch.

Hioki Electric Co., Ltd. homepage / insulation resistance meter, [Searched on September 21, 2010] Internet <URL: http://hioki.jp/pdf/field/IR40-3450sJ2-9YE-03K.pdf>

  However, the ohmmeter has the following problems to be solved. That is, in these ohmmeters, when a resistance measurement mode is selected and a voltage is input between a pair of test leads when the measure switch is not operated ( When it is mistakenly connected to the live wire), the red LED is turned on, and the voltage input between the pair of test leads on the voltage scale of the meter unit is indicated by the operated pointer. As a result, the operator recognizes that the voltage value on the voltage scale indicated by the pointer of the meter unit is the voltage input between the pair of test leads (in the ground resistance meter, the voltage on the electric wire side test lead). be able to.

  However, in these ohmmeters, the resistance scale is written together with the voltage scale in the meter section, and the swung pointer is in a state indicating the resistance value on the resistance scale as well as the voltage value on the voltage scale. The ohmmeter has a problem to be solved that an operator unfamiliar with the ohmmeter may mistakenly recognize that the resistance value on the resistance scale indicated by the pointer is the resistance to be measured. Existing.

  The present invention has been made to solve such a problem, and has as its main object to provide an ohmmeter that can avoid erroneous recognition.

In order to achieve the above object, an ohmmeter according to claim 1 is a meter unit configured to indicate a resistance scale indicated by one pointer on one scale plate, and among a resistance measurement mode and a voltage measurement mode. a mode switch for selecting one of the major switch for switching on and off of the resistance measurement, the alarm output unit, a connector test lead is connected, is connected to the connector when the resistance measuring mode while measuring the resistance to be measured via the test leads are provided with a measuring unit for measuring a voltage to be measured via the test leads connected to the connector when the voltage measurement mode, the measuring unit includes a power supply circuit, a current meter, equipped with a voltmeter and processing circuit, the ammeter and the voltmeter is always connected to the connector, the process Road measurements, when the major switch has not been operated in a state in which the resistance measurement mode is selected by the mode switch, the Rutotomoni controls the meter part to stop the operation of the pointer by the voltmeter actuates the alarm output portion when voltage with a predefined threshold voltage, which is the measurement by comparing the above said predefined threshold, the resistance measured by the mode switch When the major switch is operated in a state where the mode is selected, the power supply circuit is controlled to output either one of the measurement voltage and the measurement current, and the current measured by the ammeter And measuring the resistance of the object to be measured based on the voltage measured by the voltmeter and controlling the meter unit to drive the pointer To Ru it was pointed the resistance measured on the resistance scale by.

The resistance meter according to claim 1, wherein the measuring unit (processing circuit), a major switch in a state where the resistance measuring mode is selected by the mode selector switch is at the non-operation, was Rutotomoni, measured to stop the operation of the pointer Activate the alarm output when the voltage is above the threshold.

  Therefore, according to this ohmmeter, when the measurement switch is not operated during resistance measurement, the alarm output unit is activated when a voltage is erroneously input to the measurement unit. At the same time, the operation of the pointer is stopped by the measuring unit, and the pointer is in a state indicating ∞ on the resistance scale, that is, in a state where an effective resistance value is not indicated on the resistance scale. For this reason, the operator may cause a situation in which the resistance value is erroneously read as the resistance to be measured due to the pointer indicating an effective resistance value on the resistance scale (occurrence of erroneous recognition). It is possible to reliably confirm that the voltage is erroneously input to the measurement unit by operating the alarm output unit while avoiding it with certainty.

It is explanatory drawing for demonstrating the connection state to the grounding electrode 41 and the commercial power source line 44 of the grounding resistance meter 1. FIG. 1 is a configuration diagram of a ground resistance meter 1. FIG. It is a front view of the earthing resistance meter 1 in the state where the pointer 22 is located at the initial position.

  Hereinafter, embodiments of the resistance meter will be described with reference to the accompanying drawings. In this example, the ground resistance meter 1 will be described as an example of the resistance meter.

  First, the configuration of the ground resistance meter 1 will be described with reference to FIGS.

  The ground resistance meter 1 includes a housing 2, a meter unit 3, a ground side test lead 4, an electric wire side test lead 5, a mode switch 6, a major switch 7, an alarm output unit 8, and a measurement unit 9. As shown in FIG. 1, the housing 2 is provided with a meter unit 3, a mode switch 6, a major switch 7 and an alarm output unit 8 on the front surface thereof. The housing 2 is provided with connectors 11 and 12 to which the ground side test lead 4 and the wire side test lead 5 are connected on the upper surface (upper side surface).

  The meter unit 3 includes a scale plate 21, a pointer 22, and a drive circuit (not shown). The drive circuit drives the pointer 22 on the surface of the scale plate 21 by an angle corresponding to the voltage of the control signal S1 output from the measurement unit 9. In this example, as an example, the drive circuit uses the position indicated by the broken line in FIG. 1 as the initial position of the pointer 22 (position not driven by the drive circuit; 0 V on the voltage scale 23 and ∞ on the resistance scale 24). The pointer 22 is swung leftward (counterclockwise) by a swing angle θ corresponding to the voltage of the control signal S1. On the surface of the scale plate 21, the voltage scale 23 and the resistance scale 24 have different arcs (on concentric circles) over the entire range of the swing angle θ of the pointer 22 (the range from the initial position to the maximum swing position indicated by a one-dot chain line). It is written on the arc). The pointer 22 indicates the numerical value “0” on the voltage scale 23 and the symbol “∞” on the resistance scale 24 at the initial position described above. The meter unit 3 employs a configuration in which the pointer 22 swings around a fulcrum (a configuration that rotates), but a configuration in which the pointer 22 moves linearly can also be employed. The voltage scale 23 and the resistance scale 24 are written in parallel in parallel along the moving direction of the pointer.

  The mode change switch 6 is composed of a rotary switch as an example, and a switch position for selecting a voltage measurement mode for measuring an AC voltage (a position where a symbol “˜V” is written) and a resistance measurement mode for measuring a ground resistance. One of the switch positions (positions where the symbol “Ω” is indicated) can be selected. The mode changeover switch 6 generates mode information Dm indicating the selected mode and outputs it to the measurement unit 9. When the mode changeover switch 6 is set to the switch position where the symbol “OFF” is set, the meter unit 3, the alarm output unit 8, and the measurement unit 9 from the battery (not shown) mounted in the housing 2. Shut off the power supplied to the.

  The major switch 7 is configured as a push switch as an example, and generates and outputs a control signal S2 when operated (for example, pressed), thereby turning resistance measurement on (measurement start) and off (measurement end). Switch. The alarm output unit 8 is configured by a red LED (red light emitting diode) as an example. The alarm output unit 8 is alarm-controlled by a drive signal S3 output from the measurement unit 9. In this example, the red LED constituting the alarm output unit 8 is controlled to be turned on and shifted to the lighting state. The alarm output unit 8 is non-alarm controlled when the driving signal S3 is not output from the measurement unit 9. In this example, the red LED constituting the alarm output unit 8 is controlled to be non-lighted and is shifted to a non-lighted state. Note that the alarm output unit 8 may employ an alarm using a sound such as a buzzer instead of an alarm using light such as an LED.

  The measurement unit 9 includes a power supply circuit 31, an ammeter 32, a voltmeter 33, and a processing circuit 34, and is disposed in the housing 2. The power supply circuit 31 generates and outputs a measurement voltage Vm as an AC voltage. In this example, as an example, when the control signal S4 is input from the processing circuit 34, the power supply circuit 31 generates and outputs an alternating voltage having a predetermined voltage value (for example, AC 50V) as the measurement voltage Vm. As an example, the ammeter 32 is disposed between the power supply circuit 31 and the connector 12 to which the wire-side test lead 5 is connected, and measures a current value I1 of a current (measurement current) flowing through the wire-side test lead 5. And output to the processing circuit 34. The voltmeter 33 measures the voltage generated between the connectors 11 and 12 (that is, between the ground-side test lead 4 and the wire-side test lead 5: that is, the voltage to be measured) with reference to the potential of the ground-side test lead 4. The voltage value V1 is output to the processing circuit.

  The processing circuit 34 is configured by a CPU and a memory or dedicated hardware, and is a mode (one of a voltage measurement mode and a resistance measurement mode) indicated by mode information Dm output from the mode switch 6. In addition to the operation, in the resistance measurement mode, two operation modes (live line detection mode) are further determined based on the operation state of the major switch 7 (operating state or non-operating state) indicated by the control signal S2. And voltage output mode).

  Specifically, when operating in the voltage measurement mode, the processing circuit 34 outputs a voltage control signal S1 corresponding to the voltage value V1 measured by the voltmeter 33 to the meter unit 3, By driving (shaking) the pointer 22 with respect to the drive circuit, the voltage value V <b> 1 is indicated on the voltage scale 23.

  When the processing circuit 34 is operating in the resistance measurement mode and the measure switch 7 is not operated (not pressed in this example) (in the live line detection mode), the control signal of zero voltage is used. S1 is output to the meter unit 3 (or the output of the control signal S1 to the meter unit 3 is stopped) to cause the driving circuit of the meter unit 3 to maintain the pointer 22 at the initial position. In this state, the processing circuit 34 compares the voltage value V1 measured by the voltmeter 33 with a predetermined threshold value (AC80V as an example), and the voltage value V1 is equal to or higher than the threshold value. In this case, the driving signal S3 is output to the alarm output unit 8 to execute the lighting control. Thereby, the alarm output part 8 transfers to a lighting state. On the other hand, when the voltage value V1 is less than the threshold value, the processing circuit 34 stops the output of the drive signal S3 to the alarm output unit 8 and executes the non-lighting control. Thereby, the alarm output part 8 transfers to a non-lighting state.

  The processing circuit 34 outputs the control signal S4 to the power supply circuit 31 when the operation is in the resistance measurement mode and the measure switch 7 is operated (in the voltage output mode). While outputting the alternating voltage of the voltage value prescribed | regulated previously, the drive signal S3 is output with respect to the alarm output part 8, and lighting control is performed. In this state, the processing circuit 34 determines the resistance (resistance) between the ground-side test lead 4 and the wire-side test lead 5 based on the current value I1 measured by the ammeter 32 and the voltage value V1 measured by the voltmeter 33. Value). Further, the processing circuit 34 outputs a control signal S1 having a voltage corresponding to the measured resistance (resistance value) to the meter unit 3 to drive (swing) the pointer 22 with respect to the driving circuit of the meter unit 3. Thus, the resistance (resistance value) is indicated on the resistance scale 24.

  Next, the ground resistance measurement operation by the ground resistance meter 1 will be described with reference to FIGS. As an example, as shown in FIG. 1, a measured ground electrode 41 (hereinafter also referred to as a ground electrode 41) grounded to the ground G is used as a measurement object, and the ground resistance Rx is used as an outlet 42 installed indoors. An example of measurement by the two-electrode method will be described. In this case, a commercial power supply line 44 (live wire 45 and neutral wire 46) connected to the secondary winding of the pole transformer 43 is connected to the pair of power supply terminals 42 a and 42 b of the outlet 42. They are connected via a master breaker 48, a leakage breaker 49, and a branch breaker 50 disposed inside. A ground electrode 41 is connected to the ground terminal 42 c of the outlet 42 through a distribution board 47. Note that a resistance Ro in the figure is a grounding resistance of the neutral wire 46. In the two-electrode method, the combined resistance (Ro + Rx) of each ground resistance Rx and Ro is measured as the ground resistance.

  First, as a pretreatment for the measurement using the ground resistance meter 1, the ground side test lead 4 is connected to the ground terminal 42c of the outlet 42, and the electric wire side test lead 5 is connected to the power terminal 42b (neutral wire 46) of the outlet 42. Connected to the power supply terminal).

  Next, the mode change switch 6 is operated to measure the resistance of the mode change switch 6 at the switch position indicated by the symbol “OFF” in accordance with the switch position indicated by the symbol “Ω” as shown in FIG. Select a mode. Thereby, the supply of power to the meter unit 3, the alarm output unit 8 and the measurement unit 9 is started from the battery mounted in the housing 2, and the ammeter 32 outputs the current value I1 in the measurement unit 9, and the voltage The total 33 outputs the voltage value V1. Since the mode changeover switch 6 is in the switch position indicated by the symbol “Ω”, it outputs mode information Dm indicating the resistance measurement mode. On the other hand, since the major switch 7 has not been operated (because it has not been pressed yet), the control signal S2 is not output from the major switch 7. Therefore, the processing circuit 34 operates in the above-described live line detection mode.

  In this live line detection mode, the processing circuit 34 outputs a zero voltage control signal S1 to the meter unit 3, and maintains the pointer 22 in the initial position as shown in FIG. Let Further, the processing circuit 34 compares the voltage value V1 measured by the voltmeter 33 with a predetermined threshold value. In this case, when the wire-side test lead 5 is normally connected to the power supply terminal 42b of the outlet 42, the voltage of the wire-side test lead 5 with reference to the potential of the ground-side test lead 4 is at most about several tens of volts AC. is there. For this reason, since the voltage value V1 is less than the threshold value, the processing circuit 34 stops the output of the drive signal S3 to the alarm output unit 8 and executes the non-lighting control. Thereby, the operator can confirm that the electric wire side test lead 5 is normally connected to the power supply terminal 42b of the outlet 42 because the alarm output unit 8 is not lit in the resistance measurement mode. .

  On the other hand, when the wire-side test lead 5 is mistakenly connected to the power terminal 42a of the outlet 42 (power terminal connected to the live wire 45), the wire-side test lead 5 with reference to the potential of the ground-side test lead 4 is used. The voltage becomes AC100 volts or more. For this reason, since the voltage value V1 is equal to or greater than the threshold value, the processing circuit 34 outputs the drive signal S3 to the alarm output unit 8 and executes the lighting control. Thereby, the operator can confirm that the electric wire side test lead 5 is erroneously connected to the power terminal 42a of the outlet 42 because the alarm output unit 8 is lit in the resistance measurement mode. As a result, the electric wire side test lead 5 can be normally reconnected to the power terminal 42 b of the outlet 42. Since the voltage value V1 becomes less than the threshold value due to this reconnection, the processing circuit 34 stops the output of the drive signal S3 to the alarm output unit 8 and executes the non-lighting control. Thereby, the alarm output part 8 transfers to a non-lighting state.

  In the live line detection mode, the pointer 22 is maintained at the initial position by the processing circuit 34 as described above. For this reason, the occurrence of a situation where the resistance value indicated by the swung (driven) pointer 22 on the resistance scale 24 is erroneously read as the combined resistance (Ro + Rx) is reliably avoided.

  Subsequently, when the measure switch 7 is operated in a state where the electric wire side test lead 5 is normally connected to the power supply terminal 42b of the outlet 42, the processing circuit 34 is in the resistance measurement mode. Operates in voltage output mode.

  In this voltage output mode, the processing circuit 34 outputs the control signal S4 to the power supply circuit 31 to start outputting the measurement voltage Vm. As a result, the measurement voltage Vm is output to the connector 12 via the ammeter 32, and therefore, the electric wire side test lead 5, the power supply terminal 42 b of the outlet 42, the neutral wire 46, the ground G, the ground electrode 41, and the grounding of the outlet 42. A current flows through a path to the connector 11 via the terminal 42c and the ground side test lead 4. The ammeter 32 measures and outputs the current value I1 of this current. Further, the processing circuit 34 outputs a drive signal S3 to the alarm output unit 8 to execute lighting control. Further, the processing circuit 34 measures the resistance (resistance value) between the ground side test lead 4 and the electric wire side test lead 5 based on the current value I1 and the voltage value V1, and responds to the measured resistance (resistance value). A voltage control signal S 1 is output to the meter unit 3. In the meter unit 3, the drive circuit drives (swings) the pointer 22 by the swing angle θ corresponding to the voltage of the control signal S1. Thereby, the resistance (resistance value) is indicated on the resistance scale 24 by the pointer 22.

  Therefore, the operator can measure the combined resistance (Ro + Rx) by reading the resistance (resistance value) indicated by the pointer 22 in the meter unit 3. Further, since the alarm output unit 8 is lit, the operator can recognize that a high measurement voltage Vm is output from between the ground side test lead 4 and the wire side test lead 5. As a result, the occurrence of an accidental electric shock is greatly reduced.

  In addition, when the voltage measurement mode is selected by operating the mode changeover switch 6 to match the switch position indicated by the symbol “˜V”, the meter unit 3, the alarm from the battery mounted in the housing 2 Supply of power to the output unit 8 and the measurement unit 9 is started, and in the measurement unit 9, the voltmeter 33 outputs the voltage value V1. Further, since the mode changeover switch 6 is in the switch position indicated by the symbols “˜V”, it outputs mode information Dm indicating the voltage measurement mode. Therefore, the processing circuit 34 operates in the voltage measurement mode described above.

  In this voltage measurement mode, the processing circuit 34 outputs a voltage control signal S 1 corresponding to the voltage value V 1 output from the voltmeter 33 to the meter unit 3. In the meter unit 3, the drive circuit drives (swings) the pointer 22 by the swing angle θ corresponding to the voltage of the control signal S1. Thus, the voltage V1 of the voltage to be measured in the voltage measurement mode, that is, the voltage between the connectors 11 and 12 (in this example, the voltage between the ground side test lead 4 and the wire side test lead 5) is It is indicated on the scale 23.

  As described above, in the ground resistance meter 1, the processing circuit 34 of the measuring unit 9 operates in the live line detection mode when the measure switch 7 is not operated in the state where the resistance measurement mode is selected by the mode changeover switch 6. Then, voltage measurement of the electric wire side test lead 5 (between the ground side test lead 4 and the electric wire side test lead 5) is performed with the potential of the ground side test lead 4 as a reference in a state where the operation of the pointer 22 is stopped. When the measured voltage value V1 of the electric wire side test lead 5 is equal to or greater than the threshold value, the lighting control is performed on the alarm output unit 8.

Therefore, according to this ground resistance meter 1, when measuring the combined resistance (Ro + Rx), the electric wire side test lead 5 was erroneously connected to the power terminal 42a of the outlet 42 (the power terminal connected to the live wire 45). However, since the voltage value V1 of the electric wire side test lead 5 becomes AC100 volts or more and becomes the threshold value or more, the alarm output unit 8 is subjected to alarm control (lighting control in this example), and the alarm state (this example) Will shift to the lighting state. At the same time, the operation of the pointer 22 is stopped by the processing circuit 34, and the pointer 22 is maintained in a state indicating ∞ on the resistance scale 24, that is, in a state not indicating an effective resistance value on the resistance scale 24. The For this reason, the operator erroneously reads that the resistance value is the combined resistance (Ro + Rx) due to the pointer 22 indicating an effective resistance value on the resistance scale 24 (error recognition). while reliably avoiding the occurrence) (while prevented), by turning on the alarm output unit 8 (alarm from the alarm output unit 8), the power supply terminal 42a of electric wire test lead 5 outlet 42 (active wire 45 It is possible to confirm that it is connected to the wrong side. Thereby, since the operator can normally reconnect the electric wire side test lead 5 to the power terminal 42b of the outlet 42, the combined resistance (Ro + Rx) can be reliably measured.

  In the ground resistance meter 1 described above, the processing circuit 34 controls the alarm output unit 8 to the non-lighting state when operating in the voltage measurement mode, but adopts a configuration for shifting to the lighting state. You can also.

  In addition, as an example of the ohmmeter, the ground ohmmeter 1 has been described as an example. However, the operation of the pointer 22 is performed when the measure switch 7 is not operated in the state where the resistance measurement mode is selected by the mode changeover switch 6. Even when the voltage measurement of the measurement target is performed in the stopped state and the measured voltage is equal to or higher than the threshold value, the alarm output unit 8 is activated to shift to the alarm state. Of course it is good.

  In the ground resistance meter 1 and the insulation resistance meter described above, a configuration is used in which the measured voltage is displayed by pointing the voltage scale 23 written on the meter unit 3 with the pointer 22. In addition, it is possible to adopt a configuration in which a voltage is displayed by employing a level meter constituted by an LED or an LCD. In this configuration, the processing circuit 34 executes control for maintaining the LED and LCD of the level meter in a non-lighted state instead of the control for stopping the operation of the pointer 22 with respect to the meter unit 3 having the voltage scale 23.

  In the ground resistance meter 1 and the insulation resistance meter described above, a configuration in which the power supply circuit 31 outputs the measurement voltage Vm is employed. However, a configuration in which a measurement current is output may be employed.

DESCRIPTION OF SYMBOLS 1 Grounding resistance meter 3 Meter part 4 Grounding side test lead 5 Electric wire side test lead 6 Mode switch 7 Major switch 8 Alarm output part 9 Measuring part 21 Scale plate 22 Pointer 23 Voltage scale 24 Resistance scale

Claims (1)

A meter section in which a resistance scale pointed by one pointer is written on one scale plate, a mode selector switch for selecting one of a resistance measurement mode and a voltage measurement mode, and resistance measurement on Measure the resistance of the measurement object via the major switch that switches off, the alarm output unit, the connector to which the test lead is connected , and the test lead connected to the connector in the resistance measurement mode A measurement unit for measuring a voltage to be measured through the test lead connected to the connector in the voltage measurement mode,
The measurement unit includes a power supply circuit, an ammeter, a voltmeter, and a processing circuit,
The ammeter and the voltmeter are always connected to the connector,
It said processing circuit, when the major switch has not been operated in a state in which the resistance measurement mode is selected by the mode switch, Rutotomoni stops the operation of the pointer by controlling the meter unit, the voltmeter When the measured voltage is equal to or higher than the predetermined threshold by comparing the voltage measured by the above and a predetermined threshold, the alarm output unit is activated, and the mode selector switch When the measure switch is operated in a state in which the resistance measurement mode is selected, the power supply circuit is controlled to output either one of the measurement voltage and the measurement current, and is measured by the ammeter. Measuring the resistance of the object to be measured based on the measured current and the voltage measured by the voltmeter, and controlling the meter unit to Ohmmeter Ru was pointed the resistance measured on the resistance scale by driving the.

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