JP2001165972A - Insulation-resistance measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an insulation-resistance measuring apparatus, in which a frequency at the lowest noise level is used as the frequency of a measuring signal because the influence of noise due to changes in usage environment is avoided, in which the filtration characteristic of an input filter is made to agree automatically with the frequency of a commercial power supply and by which an insulation resistance can be measured, irrespective of whether the commercial power supply is turned on or off. SOLUTION: In this apparatus, a switched capacitor filter is used for the input filter of a detection signal, insulation resistance is measured by using the frequency at the lowest noise level existing in a low-voltage electrical circuit, the erasure band of the input filter is made to agree automatically with the frequency of the commercial power supply and its harmonics, and the input filter is removed from the detection circuit, when the commercial power supply is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation resistance measuring device for measuring the insulation resistance of an electric circuit, and more particularly to an insulation resistance measuring device configured to accurately measure the insulation resistance of a low-voltage circuit. Things.

[0002]

2. Description of the Related Art FIGS. 9 and 10 are block diagrams of a conventional insulation resistance measuring instrument.

FIG. 9 shows a conventional insulation resistance measuring device,
The measurement of the insulation resistance of a low-voltage path using the insulation resistance measurement device will be described. 1 is a high-voltage path, 2 is a low-voltage path, 3 is a transformer, C is the capacitance of the low-voltage path to ground, and R is the insulation resistance between the low-voltage path and ground. Reference numeral 6 denotes an insulation resistance measuring device. The insulation resistance measuring device 6 includes a filter 60, a synchronous detection unit 62, a display unit 63, a signal generation unit 64, and a power amplification unit 6.
5, a detection transformer 8, and an injection transformer 9. Reference numeral 10 denotes a ground line.

Next, measurement of insulation resistance on a low-voltage path using the insulation resistance measuring device 6 will be described.

[0005] First, a signal generator 64 of the insulation resistance measuring instrument 6 generates a signal having a frequency different from the frequency of the commercial power supply flowing through the low-voltage piezoelectric path to obtain a measurement signal. The measurement signal is applied to the power amplifier 65. After the power is amplified by the power amplifying unit 65, the power is injected into the ground line 10 via the injection transformer 9. The injected measurement signal is set to a predetermined voltage value, and flows from the ground line 10 through a circuit that returns to the ground line 10 through a parallel circuit of the low piezoelectric path 2, the ground capacitance C, and the insulation resistance R. Is detected by the detection transformer 8 together with the current from the commercial power supply, and is applied to the filter 60.

The filter 60 has a filtering characteristic in which the frequency of the injected measurement signal is set as a pass band, and outputs only the signal of the frequency, that is, the signal of the measurement frequency to the synchronous detection unit 62. The detection unit 62 performs synchronous detection on the signal. Since the voltage of the measurement signal injected into the ground line 10 is known as described above, the value of the insulation resistance R is obtained from the obtained current value, and the value is displayed on the display unit 63.

In FIG. 10, reference numerals 1 to 10 and reference numerals 60 to 65 denote the same block circuits as those shown in FIG. 9, and a description of these same parts will be omitted. That is, in this conventional example, an input filter 70 is added between the injection transformer 9 and the filter 60 in the conventional example shown in FIG.

In this conventional example, the voltage of the measurement signal injected from the injection transformer 9 via the signal generator 64 via the power amplifier 65 is very small as compared with the voltage of the commercial power supply existing in the low piezoelectric path 2. The signal-to-noise ratio of the measurement signal detected from the detection transformer 8 is very poor. Therefore, an input filter 70 is added,
The filtering characteristic of (1) is added to the filter 60 after improving the signal-to-noise ratio of the measurement signal as a band elimination characteristic with the frequency of the commercial power supply as the center frequency. Subsequent operations are the same as those in FIG.

[0009]

However, in order to accurately measure the insulation resistance of the low-voltage path, a low-noise frequency included in the low-voltage path is used as a measurement signal, and the pass band of the filter 60 is reduced. It is necessary to match the center frequency with the frequency of the measurement signal.

However, as the filter 60 of the insulation resistance measuring device 6 according to the prior art, a filter having a band-pass characteristic whose filtering characteristic is fixed is usually used. For this reason, even if the frequency of the noise included in the low-voltage path changes due to the conditions of the use environment, etc.
Cannot be changed, and even if the filter 60 changes due to aging or the like, the filter 60 cannot cope with the change. Therefore, there was a problem that accurate insulation resistance measurement could not be performed. Also, since the filtering characteristic of the input filter 70 is fixed similarly to the filter 60, the center frequency of the band elimination characteristic shifts when the frequency of the commercial power supply fluctuates or is affected by temperature change, aging, and the like. There is a problem that sufficient erasing characteristics cannot be obtained.

The present invention has been developed to solve each of the above problems. In order to measure the insulation resistance with high accuracy while avoiding the influence of noise accompanying a change in the use environment,
A first object is to make it possible to select the lowest frequency of the noise as the frequency of the measurement signal.

It is a second object of the present invention to automatically match the notch center frequency (center frequency of band elimination) of a conventional input filter having band elimination characteristics with the frequency of a commercial power supply. It is a third object of the present invention to enable measurement of insulation resistance irrespective of off / on of a commercial power supply.

[0013]

In order to achieve the first object, according to claim 1, an electric circuit comprising a detection transformer, a filter, a synchronous detector, a display, a signal generator, a power amplifier, and an injection transformer. In the insulation resistance measuring device for measuring the insulation resistance, a switched capacitor filter and a frequency multiplier are used in place of the filter, and a frequency controller and a voltage controlled oscillator are used in place of the signal generator. A noise detection unit is additionally provided between the output side of the capacitor filter and the input side of the frequency control unit. The frequency control unit, the voltage control oscillation unit, and the frequency multiplication unit are configured based on the noise of the electric circuit detected by the detection transformer. Using a switched capacitor filter and a noise detector to determine the frequency at which the output from the noise detector is the least, and having the determined frequency The signal for measurement is generated from the voltage control oscillator under the control of the frequency controller, and the signal for measurement is applied to the power amplifier, the frequency multiplier, and the synchronous detector. The power amplification unit amplifies the power and injects it into the ground line of the electric circuit via the injection transformer. The frequency multiplication unit multiplies the frequency of the measurement signal applied to the frequency multiplication unit by multiplying the switched capacitor filter. So that the filtering characteristic of the switched capacitor filter has a band-pass characteristic centered on the pass band at the same frequency as the frequency of the measurement signal, and the detection signal from the detection transformer is switched by the switch. An insulation resistance measuring instrument which is applied to the synchronous detection unit via a capacitor capacitor filter and displays an output from the synchronous detection unit on a display unit It is characterized.

According to a second aspect of the present invention, in the insulation resistance measuring device according to the first aspect, the frequency control unit of the insulation resistance measurement device includes an operation unit, a control unit, and a clock oscillation unit. , A frequency reduction unit, a first counter, a first digital-to-analog conversion unit, a comparator, a second counter, and a second digital-to-analog conversion unit. A control unit, a clock oscillation unit, a second counter, a second digital-to-analog conversion unit, a voltage control oscillation unit, a frequency multiplication unit, a switched capacitor filter, a noise detection unit, a comparator, a frequency reduction unit, a first counter, Using the first digital-to-analog conversion unit, a frequency with the least output from the noise detection unit is determined, and a signal having the determined frequency is converted to the second frequency.
The counter, the second digital-to-analog converter, and the voltage-controlled oscillating unit generate the measurement signal, and apply the measurement signal to the power amplifier, the frequency multiplier, and the synchronous detector. The measurement signal is power-amplified by the power amplification unit and injected into a ground line of an electric circuit via an injection transformer, and the frequency multiplication unit multiplies the frequency of the measurement signal applied to the frequency multiplication unit. And applying the same to the switched capacitor filter so that the filtering characteristic of the switched capacitor filter has a band-pass characteristic centered on a pass band at the same frequency as the frequency of the measurement signal. Is applied to the synchronous detection unit via the switched capacitor filter, and an output from the synchronous detection unit is displayed on a display unit. Is characterized in Unishi was insulation resistance meter.

According to a third aspect of the present invention, an insulation resistance of an electric circuit including a detection transformer, an input filter, a filter, a synchronous detection unit, a display unit, a signal generation unit, a power amplification unit, and an injection transformer. In an insulation resistance measuring device for measuring a signal amplification unit, one or more input switched capacitor filters, a bandpass filter, a signal adjustment unit and an input frequency multiplication unit instead of the input filter,
A signal detected by the detection transformer is applied to an input frequency multiplier through a bandpass filter and a signal adjuster, and an output from the input frequency multiplier is applied to the one or more input switched capacitor filters. The center frequency of the band elimination characteristic of the one or more input switched capacitor filters is made to match the frequency of the fundamental wave or the plurality of higher harmonics of the commercial power supply of the electric circuit, respectively, and the measurement signal generated in the signal generation unit. To the power amplifier and the synchronous detector,
The measurement signal is power-amplified in a power amplification unit and injected into a ground line of an electric circuit via an injection transformer, and a detection signal from the detection transformer is input to the signal amplification unit, the one or more input switched capacitor filters. And an insulation resistance measuring instrument which applies the output from the synchronous detection section to the detection section through a filter and displays the output on the display section.

According to a fourth aspect of the present invention, an insulation resistance of an electric circuit including a detection transformer, an input filter, a filter, a synchronous detector, a display, a signal generator, a power amplifier, and an injection transformer is provided. In the insulation resistance measuring device, a signal amplifier, one or more input switched capacitor filters, a bandpass filter, a signal adjuster, and an input frequency multiplier are used instead of the input filter, and the filter is replaced with the filter. It is configured using a switched capacitor filter and a frequency multiplier, applies a detection signal detected by a detection transformer to an input frequency multiplier through a bandpass filter and a signal adjuster, and outputs the output from the input frequency multiplier as described above. Band elimination characteristics of one or more input switched capacitor filters applied to one or more input switched capacitor filters The center frequency is adjusted to be equal to the frequency of the fundamental wave or multiple harmonics of the commercial power supply of the electric circuit, and the measurement signal generated in the signal generator is applied to the power amplifier, the frequency multiplier, and the synchronous detector. Then, the measurement signal is power-amplified in the power amplification unit and injected into the ground line of the electric circuit via the injection transformer, and the frequency of the measurement signal applied to the frequency multiplication unit is multiplied in the frequency multiplication unit. The filter is applied to a switched capacitor filter so that the filtering characteristic of the switched capacitor filter has a band-pass characteristic centered on the pass band at the same frequency as the frequency of the measurement signal. The signal is sent to the signal amplification unit,
The present invention is characterized in that an insulation resistance measuring device is applied to a synchronous detection unit via a plurality of input switched capacitor filters and the switched capacitor filter, and an output from the synchronous detection unit is displayed on a display unit.

According to a fifth aspect of the present invention, there is provided an electric circuit comprising a detection transformer, an input filter, a filter, a synchronous detector, a display, a signal generator, a power amplifier, and an injection transformer. A signal amplifying unit, one or more input switched capacitor filters, a bandpass filter, a signal adjusting unit, an input frequency multiplying unit, an input comparator, and a switch instead of the input filter. And the switch is
The path of the detection signal detected by the detection transformer is divided into a first path (detection transformer, signal amplifier, one or more input switched capacitor filters, switches, filters) and a second path (detection transformer, signal amplifier). , Switch, filter), and applies a detection signal detected by the detection transformer to the input comparator via a bandpass filter, and applies a reference voltage to the input comparator. Controlling the switch by an output obtained by comparing the two inputs, switching the first path and the second path by the switch, and detecting a detection signal detected by the detection transformer. , Applied to the input frequency multiplier through the band pass filter and the signal adjuster,
The output from the input frequency multiplier is applied to the one or more input switched capacitor filters, and the center frequencies of the band elimination characteristics of the one or more input switched capacitor filters are respectively set to the fundamental frequency of the commercial power supply in the electric circuit. To match the frequency of the multiple harmonics, apply the signal generated in the signal generation section as a measurement signal to the power amplification section and the synchronous detection section, and amplify the measurement signal in the power amplification section. And injects the detection signal from the detection transformer to the synchronous detection unit via the first path or the second path via an injection transformer, and outputs the signal from the synchronous detection unit. Is displayed on the display unit.

In order to achieve the above-mentioned second and third objects, an electric circuit comprising a detection transformer, an input filter, a filter, a synchronous detector, a display, a signal generator, a power amplifier, and an injection transformer. A signal amplifying unit, one or more input switched capacitor filters, a bandpass filter, a signal adjusting unit, an input frequency multiplying unit, an input comparator, and a switch instead of the input filter. And a switch using a switched capacitor filter and a frequency multiplying unit in place of the filter. The switch switches the path of the detection signal detected by the detection transformer to a first path (detection transformer, signal amplifying unit). , One or more input switched capacitor filters, switches, switched capacitor filters) and second
(A detection transformer, a signal amplifying unit, a switch, a switched capacitor filter), and a detection signal detected by the detection transformer is applied to the input comparator through a bandpass filter, and a reference voltage is applied. Controlling the switch by an output obtained by comparing the two inputs in the input comparator.
The switch is used to switch between the first path and the second path, and a signal detected by the detection transformer is
Applying to the input frequency multiplier through the band pass filter and the signal adjuster, applying the output from the input frequency multiplier to the one or more input switched capacitor filters,
The center frequency of the band elimination characteristics of the one or more input switched capacitor filters is made to match the frequency of the fundamental wave or the plurality of harmonics of the commercial power supply in the circuit, respectively, and the signal generated in the signal generator is measured. The measurement signal is applied to the power amplification unit, the frequency multiplication unit and the synchronization detection unit as a signal for use, and the measurement signal is amplified in the power amplification unit and injected into a ground line of an electric circuit via an injection transformer. The frequency of the measurement signal applied to the frequency multiplier is multiplied and applied to the switched capacitor filter to pass the same frequency as the frequency of the measurement signal through the filtering characteristic of the switched capacitor filter. A band pass characteristic having a center of a band is provided, and a detection signal from the detection transformer is supplied to the first path or the second path. Is applied to the synchronous detection portion through the road, it is characterized in the insulation resistance measuring device configured to display on the display unit the output of the synchronous detection unit.

In order to achieve the first, second and third objects, the present invention provides a detecting transformer, an input filter,
In an insulation resistance measuring device for measuring insulation resistance of an electric circuit including a filter, a synchronous detection unit, a display unit, a signal generation unit, a power amplification unit, and an injection transformer, a signal amplification unit instead of the input filter and one or more input switches Using a switched capacitor filter, a bandpass filter, a signal adjusting unit, an input frequency multiplying unit, an input comparator and a switch, using a switched capacitor filter and a frequency multiplying unit in place of the filter, and replacing the signal generating unit. Using a frequency control unit and a voltage control oscillation unit, a noise detection unit is additionally provided between the output side of the switched capacitor filter and the input side of the frequency control unit, and the switch is detected by a detection transformer. The path of the detected signal is changed to a first path (detection transformer, signal amplifier, one or more input switched capacitor filters, Switch, a switched capacitor filter) and a second path (detection transformer, signal amplifying unit, switch, switched capacitor filter). The detection signal detected by the detection transformer is input to the above-mentioned input through a bandpass filter. A reference voltage is applied to the input comparator while being applied to the comparator, and the switch is controlled by an output obtained by comparing the two inputs in the input comparator. A signal detected by the detection transformer is applied to an input frequency multiplier through the bandpass filter and a second signal amplifier, and an output from the input frequency multiplier is output. The voltage is applied to the one or more input switched capacitor filters, and the central frequency of the band elimination characteristic of the one or more input switched capacitor filters is reduced. The numbers are set so as to match the frequencies of the fundamental wave to the multiple harmonics of the commercial power supply on the electric circuit, respectively, and the noise of the electric circuit detected by the detection transformer is switched through the first path or the second path and switched. Capacitor filter, noise detector, frequency controller,
A voltage having the least output from the noise detection unit is obtained by using the voltage control transmission unit and the frequency multiplication unit, and a signal having the obtained frequency is generated from the voltage control oscillation unit under the control of the frequency control unit for measurement. The measurement signal is applied to the power amplification unit, the frequency multiplication unit, and the synchronization detection unit, and the measurement signal is power-amplified in the power amplification unit and injected into a ground line of an electric circuit via an injection transformer. At the same time, the frequency multiplying unit multiplies the frequency of the measurement signal applied to the frequency multiplying unit and applies the frequency to the switched capacitor filter, thereby changing the filtering characteristic of the switched capacitor filter to the measurement signal. The detection signal from the detection transformer is transmitted to the first path so as to have a band-pass characteristic having the same frequency as the frequency as the center of the pass band. Is characterized by a second path through was applied to the synchronous detection portion, the insulation resistance measuring device so as to display on the display unit the output of the synchronous detection unit.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments shown in the drawings.

FIGS. 1 and 2 are block diagrams showing a first embodiment of the present invention, and FIG. 3 shows voltage waveforms at various parts shown in FIG.

In FIG. 1, reference numeral 1 denotes a high-voltage path, 2 denotes a low-voltage path to which a low voltage stepped down by a transformer 3 is applied, 3 denotes a transformer, C denotes a low-voltage path of the low-voltage path, and R denotes a low-voltage path 2.
Is an insulation resistance measurement device, and 6 is an insulation resistance measurement device. The configuration of the insulation resistance measurement device 6 is a switched capacitor filter 61 (SCF), a synchronous detection unit 62, and a display unit 63.
, A power amplifier 65, a frequency multiplier 66, a noise detector 67, a frequency controller 68, a voltage controlled oscillator 69
(VCO), a detection transformer 8, and an injection transformer 9, and reference numeral 10 denotes a ground line.

That is, the embodiment shown in FIG. 1 uses a switched capacitor filter 61 and a frequency multiplier 66 in place of the conventional filter 60 shown in FIG. 9, and a frequency controller 68 in place of the signal generator 64. Voltage control oscillator 69
And a noise detection unit 67 is further added.

Next, using the insulation resistance measuring instrument 6 of the present invention,
The operation of the insulation resistance measuring device 6 in the low piezoelectric path 2 will be described.

First, prior to the measurement of the insulation resistance, the frequency of the lowest noise level contained in the low-voltage piezoelectric path is checked, and the insulation resistance is measured using the signal of the frequency with the lowest noise level. When the frequency control unit 68 is set to the noise level detection mode in order to detect the noise level, the frequency control unit 68 causes the voltage control oscillation unit 69 to oscillate a step-like signal sequentially from a low frequency to a high frequency. Control. At this time, the frequency control unit 68 sets the synchronous detection unit 62 and the power amplification unit 65 so as not to operate by means not shown.

The stepped signal oscillated by the voltage controlled oscillator 69 is supplied to the frequency multiplier 66 and the frequency multiplier 6
6 multiplies the signal and supplies it to a switched capacitor filter 61 having bandpass characteristics.

Here, the switched capacitor filter 6
1 has a characteristic that its filtering characteristic changes depending on the frequency of the signal to be applied, so that the frequency of the signal supplied from the frequency multiplier 66 to the switched capacitor filter 61 is
The signal from the frequency multiplier 66 is received by selecting the multiplication value of the frequency multiplier so that the center frequency of the pass band of the switched capacitor filter 61 and the frequency oscillated by the voltage controlled oscillator 69 match. The filtering characteristic of the switched capacitor filter 61 changes in accordance with the stepped signal oscillated by the voltage controlled oscillator 69 so that the center frequency of the pass band coincides with the frequency of the signal.

Therefore, when the detection signal detected by the detection transformer 8 is applied to the switched capacitor filter 61,
The switched-capacitor filter 61 selectively outputs only a narrow-band signal that matches the frequency oscillated by the voltage-controlled oscillation unit 69 to the noise detection unit 67 from the detection signal.

The noise detector 67 detects the output from the switched capacitor filter 61 and sequentially sends the output to the frequency controller 68. The frequency control unit 68 sequentially receives the output from the switched capacitor filter 61, detects the frequency with the lowest noise level, controls the voltage control oscillation unit 69, and changes the oscillation frequency of the voltage control oscillation unit 69 to the frequency. The following insulation resistance is measured with the frequency fixed at the lowest noise level.

The measurement of the insulation resistance by the insulation resistance measuring device 6 will be described below. To measure insulation resistance,
When the frequency controller 68 is set to the insulation resistance measurement mode,
The frequency control unit 68 prevents the noise detection unit 67 from operating by means (not shown), and sets the synchronous detection unit 62 and the power amplification unit 65 to an operation state.

As described above, the output from the voltage controlled oscillator 69, which maintains the state of oscillating the signal of the lowest frequency of the noise level, is used as the measurement signal and the synchronous detector 6
2. Applied to the power amplifier 65 and the frequency multiplier 66.
The power amplifier 65 amplifies the measurement signal to a required voltage and injects it into the ground line 10 via the injection transformer 9.

The injected measurement signal flows from the ground line 10, the low piezoelectric path 2, the parallel circuit of the ground capacitance C and the insulation resistance R of the low piezoelectric path 2 to the ground line 10 via the ground, and this is the low piezoelectric path 2 And the switched capacitor filter 6 is detected by the detection transformer 8 together with the current of the commercial power supply flowing through the
1 is applied.

On the other hand, the measurement signal applied to the frequency multiplier 66 is added to the switched capacitor filter 61 as a signal whose frequency has been multiplied by the frequency multiplier 66, thereby providing the switched capacitor filter 61.
, The center frequency of the pass band coincides with the frequency of the measurement signal.

Therefore, the switched capacitor filter 6
1 selectively outputs, from the detection signal detected by the detection transformer 8, only a narrow-band signal whose center frequency is the frequency of the measurement signal, and applies the signal to the synchronous detection unit 62.

The synchronous detector 62 receives the signal output from the switched capacitor filter 61 and performs synchronous detection using the measurement signal received from the voltage controlled oscillator 69 as a reference signal. Except for the phase leading current due to the influence of the ground capacitance C included in the signal received from the filter 61, only the current due to the insulation resistance R is detected, and the detected current value is output to the display unit 63. The display unit 63 calculates the value of the insulation resistance R from the current value and the known voltage value of the measurement signal injected into the ground line 10 obtained by the display unit 63 by means not shown, and calculates the result. indicate. The display unit 63 can be any means such as displaying whether or not the value of the insulation resistance R is within a normal range or displaying a numerical value.

If it is considered that the environmental conditions have changed, the above-mentioned noise level detection mode is set at any time, the frequency with the lowest noise level is checked, and the frequency of the measurement signal is changed to the frequency with the lowest noise level. Can be reset to

The switching between the noise level detection mode and the insulation resistance measurement mode can be automatically performed.

If the frequency of the measurement signal applied to the ground line 10 is lower than the frequency of the current (commercial power supply) flowing through the low piezoelectric path 2, the filtering characteristics of the switched capacitor filter 61 are applied to the ground line 10. A low-pass characteristic having a pass band equal to or lower than the frequency of the measurement signal may be used.

FIG. 2 shows an embodiment in which the inside of the frequency control unit 68 of the insulation resistor shown in FIG. 1 is shown in detail. All parts other than the frequency control unit 68 are the same as those in FIG.

In FIG. 2, reference numeral 681 denotes an operation unit, 682 denotes a control unit, 683 denotes a clock oscillation unit, 684 denotes a frequency reduction unit, 685 denotes a first counter, and 686 denotes a first digital / analog conversion unit (first D / A converter). / A), 687 is a comparator,
688 is a second counter, 689 is a second digital-to-analog converter (second D / A), and clock oscillator 6
83, the output of the frequency reduction unit 684, the first
The output of the digital-to-analog converter 686 is the output of the second digital-to-analog converter 689. FIG.
Shows waveforms of the output shown in FIG.

Next, the operation of the insulation resistance measuring instrument 6 according to the embodiment of the present invention will be described with reference to FIGS.

When the operation section 681 is set to the noise level detection mode, the control section 682 controls the display section 63 to display the fact, activates the clock oscillation section 683, and performs synchronous detection by means not shown. The power of the unit 62 and the power amplifying unit 65 is turned off to temporarily stop the functions thereof.

The clock oscillating unit 683 oscillates the clock shown in FIG. 3 and applies it to the frequency decreasing unit 684 and the second counter 688. The second counter 688 counts the clock and sequentially outputs the count value to the second digital-to-analog converter 689.

Second digital-to-analog converter 689
Receives the count value (digital value), converts it into a staircase waveform voltage (analog value) shown in FIG. Since the voltage controlled oscillator 69 has a function of oscillating a signal having a frequency proportional to the applied voltage, the voltage controlled oscillator 69 sequentially oscillates the signals of the frequencies f1 to fm in accordance with the received staircase waveform voltage. The signal is supplied to the frequency multiplier 66.

The frequency multiplier 66 sequentially multiplies the received signal and sequentially applies the received signal to the switched capacitor filter 61 as a signal of a frequency t × f1 to a frequency t × fm.

As described above, the filtering characteristics of the switched capacitor filter 61 vary depending on the applied signal. In this case, the center frequencies of the pass bands of the switched capacitor filter 61 are the frequencies f1 to f1, respectively.
By selecting the value of t to be m, the switched-capacitor filter 61 receives the signal from the frequency multiplier 66 and filters the signals of frequencies f1 to fm to be the center frequencies of the passband, respectively. The characteristics change.

When the detection signal detected by the detection transformer 8 is applied to the switched capacitor filter 61, the switched capacitor filter 61 outputs a signal that matches the frequency of the signal oscillated by the voltage controlled oscillator 69 from the detection signal, that is, the frequency. Only the signals of f1 to frequency fm are selectively output to the noise detection unit 67 sequentially.

The noise detector 67 detects the output from the switched capacitor filter 61 and outputs a DC output.
The data is sequentially transmitted to the comparator 687.

On the other hand, the output of the clock oscillating unit 683 applied to the frequency down-converting unit 684 is reduced in frequency by the frequency down-converting unit 684, and the output shown in FIG. Send to counter 685. The first counter 685 counts the input shown in (1) and sequentially outputs the count value to the first digital-to-analog converter 686. The first digital-to-analog converter 686 receives the count value (digital value), converts the count value into a staircase waveform voltage (analog value) shown in FIG.

Here, the staircase waveform voltage sequentially supplied from the first digital-to-analog converter 686 to the comparator 687 is, as shown in FIG. 3, the frequency f1 to fm of the signal output from the switched capacitor filter 61. The first one cycle which changes sequentially until the first voltage is maintained at zero voltage, and after the one cycle is completed, it is set so as to sequentially increase to the next voltage.

The comparator 687 outputs the DC output (Ein) from the noise detector 67 and the staircase waveform voltage (Ere) supplied from the first digital / analog converter 686.
f) are sequentially compared, and when the condition of Ein <Eref is satisfied, a signal is sent to the control unit 682, and the control unit 682 that has received the signal stops the clock oscillation unit 683.

If the frequency value of the signal oscillating by the voltage control oscillating unit 69 is fk when the clock oscillating unit 683 is stopped under the control of the control unit 682, the frequency fk is the highest noise level. Is determined to be a low frequency, and a signal having the frequency fk is used as a measurement signal for measuring the insulation resistance.

The insulation resistance is measured by the insulation resistance measuring device 6 as follows.

When the operation section 681 is set to the insulation resistance measurement mode, the control section 682 controls the display section 63 to display the indication, and the synchronous detection section 62 and the power amplification section 65 by means (not shown). The power supply is connected to the power supply to make the operation state, and the noise detection unit 67 and the frequency reduction unit 68
4. The first counter 685, the first digital-to-analog converter 686, and the comparator 687 are set not to operate.

As described above, with the voltage controlled oscillator 69 oscillating at the frequency fk having the lowest noise level,
The signal of the frequency fk is used as a measurement signal,
2. Applied to the power amplifier 65 and the frequency multiplier 66, the power amplifier 65 amplifies the measurement signal to a required voltage and injects it into the ground line 10 via the injection transformer 9.

The injected measurement signal is supplied to the ground line 10,
The low-voltage path 2, the parallel circuit of the ground capacitance C and the insulation resistance R of the low-voltage path 2, flows through the ground to the ground line 10, and this is detected by the detection transformer 8 together with the current of the commercial power supply flowing through the low-voltage path, and is switched. Is added to the capacitor 61.

On the other hand, the frequency multiplying unit 66 applies the frequency t × fk, which is t times the frequency of the added measurement signal, to the switched capacitor filter 61, as described above. The filtering characteristic is such that the center frequency of the pass band matches the frequency fk of the measurement signal.

Therefore, the switched capacitor filter 6
1 selectively outputs, from the detection signal detected by the detection transformer 8, only a narrow-band signal having a center frequency of the frequency fk, and adds the signal to the synchronous detection unit 62.

The synchronous detector 62 receives the output from the switched capacitor filter 61 and performs synchronous detection using the measurement signal received from the voltage controlled oscillator 69 as a reference signal. Except for the current of the leading phase due to the influence of the ground capacitance C included in the output from the device, only the current due to the insulation resistance R is detected, and the detected current value is output to the display unit 63.
Numeral 3 calculates the value of the insulation resistance R from the current value and the voltage value of the known injected measurement signal obtained by the display unit 63 by means not shown, and displays the result. The display on the display unit 63 can be an arbitrary means such as displaying whether the value of the insulation resistance R is within a normal range or displaying a numerical value.

FIG. 4 is a block diagram showing a second embodiment of the present invention. The second embodiment will be described below.

In FIG. 4, reference numerals 1 to 6, 8 to 1
Reference numerals 0, 60, 62 to 65 are the same as in the conventional example shown in FIG. 711 is a signal amplifier, 712, 713, 714
Is a first, second, and third input switched capacitor filters (one or more input SCFs), 716 is a bandpass filter, 717 is a signal adjustment unit, and 718 is an input frequency multiplication unit.

That is, the second embodiment shown in FIG.
0, a signal amplifying unit 711, a plurality of input switched capacitor filters 712, 713, and 714 are used instead of the input filter 70 shown in the conventional example of FIG.
6, a signal adjusting unit 717 and an input frequency multiplying unit 718 are used.

Next, the operation of the insulation resistance measuring instrument 6 according to the second embodiment of the present invention will be described with reference to FIG.

The detection signal detected by the detection transformer 8 is supplied to a signal amplifier 711 and a bandpass filter 716 having bandpass characteristics.
And the band pass characteristic of the bandpass filter 716 has the characteristic that the pass frequency is a little wider with the frequency fb of the commercial power supply as the center frequency, and falls within the pass band even if the frequency fb of the commercial power supply slightly shifts. Set to about. From the detection signal detected by the detection transformer 8, the frequency fb of the commercial power is selectively output to the signal adjusting unit 717 by the bandpass filter 716, and the commercial power of the frequency fb selectively output by the signal adjusting unit 717 is output. Of the input frequency multiplier 7
18 is output.

The input frequency multiplier 718 generates a frequency 2 × fb and a frequency 3 × fb from the frequency fb of the commercial power supply, and further multiplies these by a factor p to obtain a frequency p × fb and a frequency p × fb.
× 2 × fb and the frequency p × 3 × fb, the first input switched capacitor filters 712 to
, The band elimination characteristics of the first input switched capacitor filter 712 to the third input switched capacitor filter 714 are respectively set to the frequency fb, the frequency 2 × fb, and the frequency 3 × fb. By selecting the value of p so as to be the notch center frequency, the fundamental wave, the second harmonic, and the third harmonic of the commercial power supply are eliminated.

In measuring the insulation resistance, the signal generator 64
Is applied to the power amplifier 65 and the synchronous detector 62. Thereafter, the operation up to detection by the detection transformer 8 is the same as the operation in the case of FIG. Detection transformer 8
Are sequentially applied to a first input switched capacitor filter 712 to a third input switched capacitor filter 714, and the fundamental, second and third harmonics of the commercial power supply are obtained by the above-mentioned band elimination characteristics. Filters the detected signal with improved signal-to-noise ratio by eliminating waves
Send to

The filter 60 has band-pass characteristics, and its center frequency is set to the same frequency as the measurement signal generated by the signal generator 64. Therefore, only the measurement signal is selectively output to synchronize. It is applied to the detector 62. The subsequent operation is the same as the operation in FIG.

In the above embodiment, the first to third input switched capacitor filters 712 to 714 are used to improve the signal-to-noise ratio. Is a configuration of one input switched capacitor filter for only the fundamental wave, and selects the number of input switched capacitor filters and the order of harmonics for arbitrary harmonics depending on the state of waveform distortion of the commercial power supply. It is possible.

FIG. 5 is a block diagram showing a third embodiment of the present invention. The third embodiment will be described below.

In FIG. 5, reference numerals 1 to 6, 8 to 10
And 62 to 65 are the same as those in the conventional example shown in FIG.
Reference numerals 61 and 66 are the same as those in FIG. Reference numeral 711
Steps 716 to 718 are the same as those in FIG.

That is, the third embodiment shown in FIG.
0, a switched capacitor filter 61 and a frequency multiplier 66 are used instead of the filter 60, and a signal amplifier 711, a first input switched capacitor filter 712 through a third input switched filter are used instead of the input filter 70. This uses a capacitor filter 714, a bandpass filter 716, a signal adjusting unit 717, and an input frequency multiplying unit 718.

Next, the operation of the insulation resistance measuring device 6 according to the third embodiment of the present invention will be described with reference to FIG.

In measuring the insulation resistance, the signal generator 64
Is applied to the synchronous detector 62, the power amplifier 65, and the first frequency multiplier 66. The power amplifier 65 amplifies the measurement signal to a required voltage and injects it into the ground line 10 via the injection transformer 9. Thereafter, the operation up to detection by the detection transformer 8 is the same as the operation of the first embodiment shown in FIG.

The signal detected from the detection transformer 8 is transmitted to the first
4 through the input switched capacitor filter 712 through the third input switched capacitor filter 714 to output a detection signal with an improved signal-to-noise ratio to the switched capacitor filter 61. Is the same as

The subsequent operation of measuring the insulation resistance is the same as the above-described operation in the insulation resistance measurement mode in FIG.

FIG. 6 is a block diagram showing a fourth embodiment of the present invention. The fourth embodiment will be described below.

In FIG. 6, reference numerals 1 to 6, 8 to 1
Reference numerals 711 to 714 and 716 to 718 are the same as those in the conventional example shown in FIG.
Is the same as Reference numeral 715 is a switch, 719 is an input comparator, and terminal V.ref is an input terminal for a reference voltage.

That is, the fourth embodiment shown in FIG.
0 instead of the input filter 70 shown in FIG.
1, using a first input switched capacitor filter 712 to a third input switched capacitor filter 714, a bandpass filter 716, a signal adjusting unit 717, and an input frequency multiplying unit 718, an input comparator 719, and a reference voltage input Terminal V.ref is added.

Next, the operation of the insulation resistance measuring device 6 according to the fourth embodiment of the present invention will be described with reference to FIG.

The detection signal detected by the detection transformer 8 is filtered by a band-pass filter 716 having a band-pass characteristic, and only the frequency of the commercial power supply is input to the input comparator 719 and the signal adjusting unit 717.
Is added to The input comparator 719 further has a terminal V.ref.
, And compares the reference voltage with the voltage based on the trademark power supply input to the input comparator 719 via the bandpass filter 716 to obtain an input comparator 719
The switch 715 is controlled by the output of.

The switch 715 switches the path of the detection signal detected by the detection transformer 8 to the first path (detection transformer 8,
The signal amplifying unit 711, the first to third input switched capacitor filters 712 to 714, the switch 715 and the filter 60) and the second
(The detection transformer 8, the signal amplifying unit 711, the switch 715, and the filter 60).

When the input from the bandpass filter 716 is higher than the reference voltage, the input comparator 719 determines that the commercial power supply is on, sets the first path, and sets the input from the bandpass filter 716 as input. Is lower than the reference voltage, it is determined that the commercial power supply is off, and the switch 715 is controlled to switch to the second path.

When the commercial power is off, the bandpass filter 71
6, there is almost no output, so that the input frequency multiplying unit 71
8, the operations of the first input switched capacitor filter 712 to the third input switched capacitor filter 714 become unstable, and these circuits become unnecessary, so that the signal from the signal amplification unit The output is sent directly to the filter 60 via the switch 715.

The switch 715 and the input comparator 719
The operation other than the operation related to FIG.

FIG. 7 is a block diagram showing a fifth embodiment of the present invention. The fifth embodiment will be described below.

In FIG. 7, reference numerals 1 to 6, 8 to 1
Reference numerals 0, 62 to 65 are the same as those in the conventional example shown in FIG.
Reference numerals 61 and 66 are the same as those in FIG. Reference numerals 711 to 714 and 716 to 718 are the same as those in FIG. 71
9 and the terminal V.ref are the same as in FIG.

That is, the fifth embodiment shown in FIG.
0, a switched capacitor filter 61 and a frequency multiplier 66 are used in place of the filter 60, and a signal amplifier 711, first input switched capacitor filters 712 to third input switched are used in place of the input filter 70. A capacitor filter 714, a bandpass filter 716, a signal adjuster 717, and an input frequency multiplier 718 are used, and an input comparator 719 and an input terminal V.ref of a reference voltage are added.

Next, the operation of the insulation resistance measuring device 6 according to the fifth embodiment of the present invention will be described with reference to FIG.

The signal amplifying section 711, the first to third input switched capacitor filters 712 to 714, the band pass filter 716, the signal adjusting section 717, the input frequency multiplying section 718, and the switch 715
The operation of the input comparator 719 is the same as the operation of FIG. The operation other than the above is the same as the operation in the case of FIG.

FIG. 8 is a block diagram showing a sixth embodiment of the present invention, which will be described below based on the sixth embodiment.

In FIG. 8, reference numerals 1 to 6, 8 to 1
Reference numerals 0, 62, 63 and 65 are the same as those in the conventional example shown in FIG. Reference numerals 61 and 66 to 69 are the same as those in FIG.
Reference numerals 711 to 714 and 716 to 718 are the same as those in FIG. Reference numeral 719 and terminal V.ref are the same as those in FIG.

That is, the sixth embodiment shown in FIG.
0, a switched capacitor filter 61 and a frequency multiplier 66 are used instead of the filter 60, and a signal amplifier 711, a first input switched capacitor filter 712 through a third input switched filter are used instead of the input filter 70. A capacitor filter 714, a bandpass filter 716, a signal amplifying unit 717 and an input frequency multiplying unit 718 are used, and a frequency control unit 68 and a voltage controlled oscillator 69 are used instead of the signal generating unit 64. The comparator 719 adds a reference voltage input terminal V.ref.

Next, the operation of the insulation resistance measuring instrument 6 according to the sixth embodiment of the present invention will be described with reference to FIG.

A switched capacitor filter 61, a frequency multiplier 66, a noise detector 67, a frequency controller 68,
The operation of detecting the frequency with the lowest noise level using the voltage controlled oscillator 69 and using the signal of this frequency as the measurement signal is the same as the operation in FIG.

Operations other than those described above are the same as those in the case of the fifth embodiment shown in FIG. The frequency control unit 68 shown in FIG. 8 is replaced with the operation unit 681 and the control unit 68 shown in FIG.
2. Clock oscillation unit 683, frequency reduction unit 684, first
Counter 685, first digital-to-analog converter 6
86, a comparator 687, a second counter 688, and a second digital-to-analog converter 689.

[0096]

As described above, according to the insulation resistance measuring instrument of the present invention, the lowest frequency of the noise level existing in the low piezoelectric path is detected in advance, and the frequency is applied to measure the insulation resistance. In addition, it is possible to prevent the measurement error of the insulation resistance due to noise, and it is not affected by noise even if the detection signal detected from the detection transformer is weak due to the high insulation resistance of the low piezoelectric path. There is an effect that high insulation resistance measurement can be performed.

A first input switched capacitor filter 712 to a third input switched capacitor filter 714 having band elimination characteristics are provided between the signal amplifying unit 711 and the filter 60 or the switched capacitor filter 61. By automatically matching the center frequency of each notch to the fundamental wave, second harmonic, and third harmonic of the commercial power supply, the signal-to-noise ratio in insulation resistance measurement can be greatly improved. is there.

Further, the voltage of the commercial power supply is monitored by the comparator 719. When the commercial power supply is off, the first to third input switched capacitor filters 712 to 714 are bypassed by the switch 715. This also has the effect that the insulation resistance can be measured regardless of whether the commercial power is on or off.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of an insulation resistance measuring device according to the present invention.

FIG. 2 is a detailed block diagram showing a first embodiment of the insulation resistance measuring device according to the present invention.

FIG. 3 is a diagram showing output waveforms of respective units in FIG. 2;

FIG. 4 is a detailed block diagram showing a second embodiment of the insulation resistance measuring device according to the present invention.

FIG. 5 is a detailed block diagram showing a third embodiment of the insulation resistance measuring device according to the present invention.

FIG. 6 is a detailed block diagram showing a fourth embodiment of the insulation resistance measuring device according to the present invention.

FIG. 7 is a detailed block diagram showing a fifth embodiment of the insulation resistance measuring device according to the present invention.

FIG. 8 is a detailed block diagram showing a sixth embodiment of the insulation resistance measuring device according to the present invention.

FIG. 9 is a block diagram showing a conventional insulation resistance measuring instrument.

FIG. 10 is a block diagram showing a conventional insulation resistance measuring instrument.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... High-voltage path 2 ... Low-voltage path 3 ... Transformer C ... Low-voltage path ground resistance R ... Low-voltage path insulation resistance to ground 6 ... Insulation resistance measuring instrument 8 ... Detection transformer 9 ... Injection transformer 10 ... Grounding line 60 ... Filter 61 ... switched capacitor filter 62 ... synchronous detector 63 ... display 64 ... signal generator 65 ... power amplifier 66 ... frequency multiplier 67 ... noise detector 68 ... frequency controller 69 ... voltage control oscillator 681 ... operation Unit 682 control unit 683 clock oscillation unit 684 frequency reduction unit 685 first counter 686 first digital-analog converter 687 comparator 688 second counter 689 second digital-analog converter 711 ... Signal amplification section 712 first input switched capacitor filter 713 second input switched capacitor filter 714: third input switched capacitor filter 715: switch 716: bandpass filter 717: signal adjuster 718: input frequency multiplier 719: input comparator

Claims (7)

[Claims] A detecting transformer, a filter, a synchronous detector,
In an insulation resistance measuring device for measuring an insulation resistance of an electric circuit including a display unit, a signal generation unit, a power amplification unit, and an injection transformer, a switched capacitor filter and a frequency multiplication unit are used instead of the filter, and the signal generation unit is used. Instead, a frequency control unit and a voltage control oscillation unit are used, and a noise detection unit is additionally provided between the output side of the switched capacitor filter and the input side of the frequency control unit, and the electric circuit detected by the detection transformer is used. From the noise, a frequency control unit, a voltage control oscillation unit, a frequency multiplication unit, a switched capacitor filter, and a noise detection unit are used to obtain a frequency with the least output from the noise detection unit, and a signal having the obtained frequency is obtained. Is generated from the voltage controlled oscillator under the control of the frequency controller, and is used as a measurement signal. It is applied to the frequency multiplier and the synchronous detector, and the measurement signal is power-amplified in the power amplifier and injected into a ground line of an electric circuit via an injection transformer, and is also applied to the frequency multiplier in the frequency multiplier. The frequency of the added measurement signal is multiplied and applied to the switched capacitor filter, and the filtering characteristic of the switched capacitor filter is set to a band whose center is a pass band at the same frequency as the frequency of the measurement signal. A pass characteristic is provided, a detection signal from the detection transformer is applied to the synchronous detection unit through the switched capacitor filter, and an output from the synchronous detection unit is displayed on a display unit. And insulation resistance measuring instrument. 2. The insulation resistance measurement device according to claim 1, wherein the frequency control unit of the insulation resistance measurement device includes an operation unit, a control unit, a clock oscillation unit, a frequency reduction unit, a first counter,
It comprises a first digital-to-analog converter, a comparator, a second counter, and a second digital-to-analog converter. The operation unit, the control unit, the clock oscillating unit, the second A counter, a second digital-to-analog converter, a voltage controlled oscillator, a frequency multiplier, a switched capacitor filter, a noise detector, a comparator,
Using a frequency down converter, a first counter, and a first digital-to-analog converter, a frequency at which the output from the noise detector is minimized is determined, and a signal having the determined frequency is determined by the second counter, the second counter. 2, a measurement signal generated by the operation of the digital-to-analog conversion unit and the voltage control oscillation unit, and the measurement signal is applied to the power amplification unit, the frequency multiplication unit, and the synchronous detection unit, and the measurement signal is
The power amplifying unit amplifies the power and injects it into a ground line of an electric circuit via an injection transformer. The frequency multiplying unit multiplies the frequency of the measurement signal applied to the frequency multiplying unit by multiplying the switched capacitor. Applied to the filter to change the filtering characteristics of the switched capacitor filter,
A bandpass characteristic having the same frequency as the frequency of the measurement signal as the center of the passband is provided, and a detection signal from the detection transformer is applied to the synchronous detection unit via the switched capacitor filter. An insulation resistance measuring instrument characterized in that an output from a synchronous detection section is displayed on a display section. 3. An insulation resistance measuring device for measuring insulation resistance of an electric circuit comprising a detection transformer, an input filter, a filter, a synchronous detector, a display, a signal generator, a power amplifier, and an injection transformer, wherein the input filter is replaced with the input filter. A signal amplifier, one or more input switched capacitor filters,
It is configured using a bandpass filter, a signal adjustment unit and an input frequency multiplication unit, and a signal detected by the detection transformer is applied to the input frequency multiplication unit via the bandpass filter and the signal adjustment unit. The output is applied to the one or more input switched capacitor filters, and the center frequencies of the band elimination characteristics of the one or more input switched capacitor filters are respectively set to the frequencies of the fundamental wave to the multiple harmonics of the commercial power supply in the electric circuit. And apply the measurement signal generated in the signal generation unit to the power amplification unit and the synchronous detection unit, and power-amplify the measurement signal in the power amplification unit and supply the electric signal through the injection transformer. The detection signal from the detection transformer is injected into a ground line, and the detection signal is passed through the signal amplification unit, the one or more input switched capacitor filters, and the filter. Is applied to the wave portion, the insulation resistance measuring instrument is characterized in that so as to display on the display unit the output from the synchronous detection unit. 4. An insulation resistance measuring device for measuring the insulation resistance of an electric circuit comprising a detection transformer, an input filter, a filter, a synchronous detector, a display, a signal generator, a power amplifier, and an injection transformer, wherein the input filter is replaced with the input filter. A signal amplifier, one or more input switched capacitor filters,
Using a bandpass filter, a signal adjustment unit and an input frequency multiplication unit,
Further, the filter is constituted by using a switched capacitor filter and a frequency multiplier in place of the filter, and a detection signal detected by a detection transformer is applied to an input frequency multiplier through a bandpass filter and a signal adjuster, and the input frequency multiplier is applied. The output from the section is applied to the one or more input switched capacitor filters, and the center frequency of the band rejection characteristic of the one or more input switched capacitor filters is respectively changed from the fundamental wave to the multiple harmonics of the commercial power supply in the electric circuit. The frequency of the wave is made to match, the measurement signal generated in the signal generator is applied to the power amplifier, the frequency multiplier and the synchronous detector, and the power for the measurement signal is amplified in the power amplifier. The signal is injected into the ground line of the electric circuit via the injection transformer, and the frequency of the measurement signal applied to the frequency multiplier in the frequency multiplier. Is applied to the switched capacitor filter, and the filtering characteristic of the switched capacitor filter is set to have a band-pass characteristic centered on a pass band at the same frequency as the frequency of the measurement signal. To the synchronous detection unit via the signal amplification unit, the one or more input switched capacitor filters, and the switched capacitor filter, and output from the synchronous detection unit is displayed on a display unit. An insulation resistance measuring device characterized by the following. 5. An insulation resistance measuring device for measuring the insulation resistance of an electric circuit comprising a detection transformer, an input filter, a filter, a synchronous detector, a display, a signal generator, a power amplifier, and an injection transformer, wherein the input filter is replaced with the input filter. A signal amplifier, one or more input switched capacitor filters,
It is configured using a bandpass filter, a signal adjusting unit, an input frequency multiplying unit, an input comparator, and a switch. The switch switches the path of the detection signal detected by the detection transformer into a first path (detection transformer, signal amplification And a function of switching between one or more input switched capacitor filters, switches, and filters) and a second path (detection transformer, signal amplifying unit, switch, and filter). Applying a reference voltage to the input comparator via a bandpass filter, applying a reference voltage to the input comparator, and controlling the switch by an output obtained by comparing the two inputs in the input comparator; To switch between the first path and the second path. The detection signal detected by the detection transformer is transmitted to the band-pass filter and the signal adjustment unit. And applying the output from the input frequency multiplier to the one or more input switched capacitor filters to obtain the center frequency of the band elimination characteristic of the one or more input switched capacitor filters. To the frequencies of the fundamental wave to the multiple harmonics of the commercial power supply of the electric circuit, respectively, and apply the signal generated in the signal generation unit as a measurement signal to the power amplification unit and the synchronous detection unit, and The signal is power-amplified in the power amplifying unit, injected into a ground line of an electric circuit via an injection transformer, and a detection signal from the detection transformer is sent to the synchronous detection unit via the first path or the second path. The insulation resistance measuring device, wherein the output is applied to the display and the output of the synchronous detection unit is displayed on the display unit. 6. An insulation resistance measuring device for measuring the insulation resistance of an electric circuit comprising a detection transformer, an input filter, a filter, a synchronous detector, a display, a signal generator, a power amplifier, and an injection transformer, wherein the input filter is replaced with the input filter. A signal amplifier, one or more input switched capacitor filters,
A band filter, a signal adjusting unit, an input frequency multiplying unit, an input comparator and a switch are used, and a switched capacitor filter and a frequency multiplying unit are used instead of the above filter, and the switch is detected by a detecting transformer. The path of the detected signal is changed to a first path (detection transformer, signal amplifier, one or more input switched capacitor filters,
A function of switching between a switch and a switched capacitor filter) and a second path (a detection transformer, a signal amplifying unit, a switch and a switched capacitor filter). A reference voltage is applied to the input comparator, and a reference voltage is applied to the input comparator. The switch is controlled by an output obtained by comparing the two inputs at the input comparator, and the first path is controlled by the switch. And the second path is switched, a signal detected by the detection transformer is applied to an input frequency multiplier through the bandpass filter and a signal adjuster, and an output from the input frequency multiplier is output to the first frequency multiplier. To a plurality of input switched capacitor filters,
The center frequency of the band elimination characteristic of the plurality of input switched capacitor filters is made to match the frequency of the fundamental wave or the plurality of harmonics of the commercial power supply of the electric circuit, and the signal generated by the signal generation unit is measured. As a power amplifier, a frequency multiplier and a synchronization detector are applied, and the measurement signal is power-amplified in the power amplifier and injected into a ground line of an electric circuit via an injection transformer. The frequency of the measurement signal applied to the frequency multiplier is multiplied and applied to the switched capacitor filter, and the filtering characteristic of the switched capacitor filter is changed to the same frequency as the frequency of the measurement signal in the pass band. A bandpass characteristic having a center is provided, and a detection signal from the detection transformer is transferred to the first path or the second path. After applied to the synchronous detection portion, the insulation resistance measuring instrument is characterized in that so as to display on the display unit the output of the synchronous detection unit. 7. An insulation resistance measuring device for measuring the insulation resistance of an electric circuit comprising a detection transformer, an input filter, a filter, a synchronous detector, a display, a signal generator, a power amplifier, and an injection transformer, wherein the input filter is replaced with the input filter. A signal amplifier, one or more input switched capacitor filters,
A bandpass filter, a signal adjusting unit, an input frequency multiplier, an input comparator and a switch are used, and a switched capacitor filter and a frequency multiplier are used instead of the filter, and a frequency controller and a signal generator are used instead of the signal generator. A voltage control oscillator is used, and a noise detection unit is additionally provided between the output side of the switched capacitor filter and the input side of the frequency control unit, and the switch detects the detection signal detected by the detection transformer. The path is divided into a first path (detection transformer, signal amplifier, one or more input switched capacitor filters, switches, switched capacitor filters) and a second path (detection transformer, signal amplifier, switch, switched capacitor). Filter), and has a function of switching the detection signal detected by the detection transformer through the bandpass filter to the input comparator. In addition, a reference voltage is applied to the input comparator, and the switch is controlled by an output obtained by comparing the two inputs in the input comparator, and the first path and the second path are controlled by the switch. A signal detected by the detection transformer is applied to an input frequency multiplier through the band pass filter and a second signal amplifier, and an output from the input frequency multiplier is output from the above-mentioned 1 to It is applied to a plurality of input switched capacitor filters so that the center frequencies of the band elimination characteristics of the one or more input switched capacitor filters match the frequencies of the fundamental wave to the multiple harmonics of the commercial power supply in the electric circuit, respectively. None, from the noise of the electric circuit detected by the detection transformer, via the first path or the second path, the switched capacitor filter, the noise detection unit, Number control unit,
A voltage having the least output from the noise detection unit is obtained by using the voltage control transmission unit and the frequency multiplication unit, and a signal having the obtained frequency is generated from the voltage control oscillation unit under the control of the frequency control unit for measurement. The measurement signal is applied to the power amplification unit, the frequency multiplication unit, and the synchronization detection unit, and the measurement signal is power-amplified in the power amplification unit and injected into a ground line of an electric circuit via an injection transformer. At the same time, the frequency multiplying unit multiplies the frequency of the measurement signal applied to the frequency multiplying unit and applies the frequency to the switched capacitor filter, thereby changing the filtering characteristic of the switched capacitor filter to the measurement signal. The detection signal from the detection transformer is transmitted to the first path so as to have a band-pass characteristic having the same frequency as the frequency as the center of the pass band. Insulation resistance meter being characterized in that so as to through the second path is applied to the synchronous detection unit, the display unit the output of the synchronous detection unit.