JP2015179012A - Frequency detection device and measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a frequency detection device which offers reduced size and cost.SOLUTION: A frequency detection device includes; an antenna 11 which receives power supply noise Sn having a frequency that is same as a power supply frequency f of an AC voltage Vac generated from a power supply circuit 2 which receives the AC voltage Vac and which outputs a detection signal S1 having a waveform similar to that of the AC supply Vac; a binarization circuit 13 which binarizes the detection signal S1 and outputs a binarized signal S2; and a processing unit 14 which performs a frequency detection process which detects the power supply frequency f by detecting a frequency of the binarized signal S2.

Description

  The present invention relates to a frequency detection device that detects a power supply frequency of an AC power supply, and a measurement device that includes the frequency detection device and measures a parameter to be measured.

  As a frequency detection device for detecting the power supply frequency of an AC power supply, the present applicant has already proposed a power supply frequency detection circuit used in an electric measuring instrument disclosed in Patent Document 1 below. This power frequency detection circuit includes a resistor, a surge absorber, a diode, a photocoupler including a light emitting diode and a light receiving transistor, an A / D converter, and an arithmetic control unit (CPU).

  In this power supply frequency detection circuit, the resistor limits the power supply voltage to a voltage level that can be applied to the light emitting diode, the surge absorber absorbs noise contained in the power supply voltage, and the diode emits a half wave of one cycle of the power supply voltage. Apply to the diode. The light emitting diode emits light when a power supply voltage is applied, and transmits a pulse signal having the same frequency as the power supply voltage to the light receiving transistor. The A / D converter converts the pulse signal from analog to digital, and the operation control unit reads the state of “H”. When the period of “H” is 16.7 ms, the power supply frequency is 60 Hz, and when it is 20 ms, 50 Hz. Is detected.

JP-A-9-43280 (2nd page, FIG. 7)

  However, the above-described frequency detection device has the following problems to be improved. That is, in this frequency detection device, a circuit component on the side of a power supply voltage (commercial AC voltage) such as AC 100 V and a circuit component on the side of a weak current operation unit such as an arithmetic control unit including a CPU are insulated via a photocoupler. Because of the configuration, the circuit component on the power supply voltage side, the photocoupler, and the circuit component on the weak current operating unit side are normally mounted on one circuit board, and the circuit component on the power supply voltage side and this circuit component Since the wiring pattern for connecting the terminals must be arranged with a sufficient insulation distance corresponding to the power supply voltage, the circuit board becomes large. For this reason, this frequency characteristic device has a problem that it is difficult to reduce the size of the device because it is necessary to secure a large mounting space for the circuit board. In addition, this frequency characteristic device requires not only the circuit component on the weak current operating unit side, but also the circuit component and the photocoupler on the power supply voltage side, so that the device cost increases as the number of components increases. is there.

  The present invention has been made in view of such a problem to be improved, and a main object of the present invention is to provide a frequency detection device that can be reduced in size and reduced in cost. Another main object is to provide a measuring apparatus including the frequency measuring apparatus.

  In order to achieve the above object, the frequency detection device according to claim 1 receives power supply noise having the same frequency as the power supply frequency of the AC voltage generated from the power supply circuit to which the AC voltage is input, and the waveform of the AC power supply. An antenna that outputs a detection signal having a similar waveform, a binarization circuit that binarizes the detection signal and outputs it as a binarized signal, and detects the power supply frequency by detecting the frequency of the binarized signal And a processing unit that executes frequency detection processing.

  According to a second aspect of the present invention, there is provided a measurement apparatus according to the first aspect, an A / D conversion unit that samples a measurement target signal acquired from a measurement target and converts it into digital data, and a predetermined number of the digital signals. A calculation unit that calculates a parameter to be measured based on data, and the calculation unit is configured to calculate the number for the calculation process based on the power supply frequency detected by the frequency detection device. Is specified.

  According to the frequency detection device of claim 1, an electronic component that operates at a low voltage (a low voltage such as +5 V, for example, a low voltage compared to an AC voltage that is a commercial voltage) such as a binarization circuit and a processing unit. Therefore, it has an electronic component to which an alternating voltage that is a high voltage is applied and an electronic component to which a low voltage is applied, and these electronic components are connected in an electrically insulated state. Unlike conventional frequency detection devices that use photocouplers, all electronic components and wiring with an insulation distance that is extremely shorter than the insulation distance that must be secured for electronic components and wiring patterns to which AC voltage is applied The pattern can be placed on a circuit board. Thereby, according to this frequency detection apparatus, an apparatus can be reduced in size significantly. In addition, electronic components to which an AC voltage is applied (high-voltage electronic components) and photocouplers are generally expensive, but according to this frequency detection device, such electronic components can be made unnecessary. Costs can be reduced.

  Moreover, according to the measuring apparatus of Claim 2, since the frequency detection apparatus of Claim 1 which can be reduced in size is provided, a measuring apparatus can also be reduced in size easily. Moreover, according to this measuring apparatus, the product cost of the measuring apparatus can be reduced by providing the frequency detecting apparatus according to claim 1 capable of reducing the product cost.

It is a block diagram which shows each structure of the frequency detection apparatus 3 and the insulation resistance measuring apparatus 1 which has this frequency detection apparatus 3. FIG. 3 is a circuit diagram of the frequency detection device 3. FIG. It is explanatory drawing for demonstrating operation | movement of the insulation resistance measuring apparatus 1. FIG.

  Hereinafter, embodiments of a frequency detection device and a measurement device will be described with reference to the accompanying drawings.

  The insulation resistance measuring device 1 shown in FIG. 1 is an example of a “measuring device” configured to include a “frequency detecting device”, and includes a power supply circuit 2, a frequency detecting device 3, and a resistance measuring circuit 4 to perform measurement. A parameter of the object 100 (specifically, a resistance value (insulation resistance value in this example) R between the pair of parts P1 and P2 in the measurement object 100) is measured.

  As an example, the power supply circuit 2 is configured as a switching power supply circuit having an insulating transformer, and an AC voltage Vac (in this example, AC 100 V of commercial frequency (50 Hz or 60 Hz) input to the primary winding side of the insulating transformer. ) To generate and output a DC voltage Vdc for operating each component constituting the insulation resistance measuring apparatus 1.

  The frequency detection device 3 includes an antenna 11, a filter circuit 12, a binarization circuit 13, and a processing unit 14, and is configured to be able to detect the power supply frequency f of the AC voltage Vac. The antenna 11 is a wiring pattern (loop pattern or zigzag wiring pattern formed on the surface of a circuit board (not shown) on which the filter circuit 12, the binarization circuit 13, the processing unit 14, and the like are mounted. As shown in FIG. 2, it is formed in a zigzag shape. Further, the antenna 11 is disposed in the non-contact state (separated state) with respect to the power supply circuit 2 in the vicinity of the power supply circuit 2, specifically, in the vicinity of the primary side of the insulation transformer of the power supply circuit 2. . The antenna 11 has one end open and the other end connected to the filter circuit 12. With this configuration, the antenna 11 receives power supply noise (hum noise) Sn having the same frequency as the power supply frequency of the AC voltage Vac generated from the power supply circuit 2 to which the AC voltage Vac is input, and AC based on the power supply noise Sn. A detection signal S1 having a waveform (AC waveform) similar to the waveform of the voltage Vac is output.

  The filter circuit 12 is composed of a low-pass filter, and passes a signal having the same frequency as the power supply frequency f of the AC voltage Vac input to the power supply circuit 2 and blocks a signal having a frequency exceeding the power supply frequency f. (It shall also include passing the signal level significantly attenuated). Thereby, the filter circuit 12 removes high frequency components (such as switching noise components radiated from the power supply circuit 2) included in the detection signal S1. In this example, as an example, the filter circuit 12 includes a capacitor (bypass capacitor) 12a disposed between the other end of the antenna 11 and a reference potential portion (ground G), as shown in FIG. However, it can also be constituted by various low-pass filters such as an RC filter using a resistor and a capacitor and an LC filter using a coil and a capacitor.

  As an example, the binarization circuit 13 includes an active filter including an operational amplifier 13a, an input resistor 13b, two feedback resistors 13c and 13d for gain setting, and a feedback capacitor 13e. As an example, the operational amplifier 13 a is configured as a non-inverting amplifier by feedback resistors 13 c and 13 d and operates at +5 V, which is one of the DC voltages Vdc output from the power supply circuit 2. Further, the operational amplifier 13a amplifies the detection signal S1 with a very large gain and outputs it when the resistance value of the feedback resistor 13d is set to a sufficiently large value with respect to the resistance value of the feedback resistor 13c. Specifically, when the positive detection signal S1 is input, the operational amplifier 13a amplifies the detection signal S1 to the power supply voltage (+5 V in this example) and outputs the amplified signal. On the other hand, when the negative voltage detection signal S1 is input, the operational amplifier 13a amplifies and outputs the detection signal S1 to a reference potential (the potential of the ground G, 0 volts).

  With this configuration, the operational amplifier 13a detects a detection signal S1 as an AC signal input via the input resistor 13b as a rectangular wave signal (high level is + 5V and low level is 0 volts (ground potential)). A signal having the same frequency as the detection signal S1 and a duty ratio of 0.5), that is, a binary signal (digital data) S2 is converted and output. In the operational amplifier 13a, the feedback capacitor 13e is connected in parallel to the feedback resistor 13d connected between the output terminal and the inverting input terminal. Therefore, the resistance value of the feedback resistor 13d and the capacitance value of the feedback capacitor 13e. It functions as an active low-pass filter whose cutoff frequency is the frequency specified by. Thereby, the operational amplifier 13a removes the high frequency component contained in the input detection signal S1, and outputs the binarized signal S2.

  In this example, the binarization circuit 13 includes the operational amplifier 13a configured as a non-inverting amplifier. However, the operational amplifier 13a can also be configured as an inverting amplifier. S1 can be converted into a rectangular wave signal having an H level of +5 V and an L level of 0 volts, that is, a binarized signal (digital data) S2, and can be output. In this example, the operational amplifier 13a functions as an active low-pass filter by connecting the feedback capacitor 13e to the operational amplifier 13a. However, when the filter circuit 12 can sufficiently remove unnecessary frequency components. Of course, a configuration in which the feedback capacitor 13e is not connected may be adopted. Although not shown, a binarization circuit may be configured by an amplification circuit that amplifies the detection signal S1 and a comparator that binarizes the signal amplified by the amplification circuit with a threshold value. However, it is preferable to configure the binarization circuit 13 with one operational amplifier 13a as in the circuit configuration shown in FIG. 2 from the viewpoint of simplifying the configuration.

  In addition, even if a binarization circuit that uses the amplifier circuit and the comparator as described above is slightly complicated (complex compared to the binarization circuit 13 having the configuration shown in FIG. 2), Since the frequency detection device 3 of this example is composed of only electronic components that operate at a low voltage compared to a frequency detection device configured to use a conventional photocoupler, the frequency detection device 3 should be mounted in a sufficiently small mounting space. Is possible.

  The processing unit 14 includes, for example, a plurality of A / D converters and a CPU (all not shown). The processing unit 14 operates based on an operation program stored in advance in the storage unit 24 to be described later, and performs frequency detection processing (processing for detecting the power supply frequency f of the AC voltage Vac), thereby detecting the frequency. It functions as a component of a part of the device 3. In addition, the processing unit 14 operates based on the operation program and executes arithmetic processing (processing for calculating the resistance value R) as will be described later, thereby constituting a part of the insulation resistance measuring device 1. Also functions as (calculation unit).

  As shown in FIG. 1, the resistance measurement circuit 4 includes a voltage output unit 21, a current detection unit 22, a voltage detection unit 23, a storage unit 24, an output unit 25, and a processing unit 14. The voltage output unit 21 is composed of, for example, a DC power supply that can change the output voltage, and is controlled by the processing unit 14 to thereby control the DC voltage Vo (for example, DC 500 V, DC) of the test voltage value specified by the processing unit 14. DC voltage of a high test voltage value such as DC 1000V) is output between the pair of probes PL1 and PL2.

  The current detection unit 22 is disposed in the output loop of the DC voltage Vo by the voltage output unit 21, detects the current (DC current) Ii flowing in the output loop, and detects the detected current Ii (from the measurement object 100). A voltage signal Si whose voltage value changes in proportion to the current value of the acquired measurement target signal) is generated and output to the processing unit 14. The voltage detection unit 23 detects the voltage Vi generated between the pair of probes PL1 and PL2 when the current Ii flows in the output loop of the DC voltage Vo, and detects the detected voltage Vi (the other voltage acquired from the measurement object 100). A voltage signal Sv whose voltage value changes in proportion to the voltage value of the measurement target signal) is generated and output to the processing unit 14.

  As described above, the processing unit 14 functions as a part of the components of the insulation resistance measuring apparatus 1, samples the voltage signal Si output from the current detection unit 22 with an A / D converter, and converts it into digital data Di. At the same time, the voltage signal Sv output from the voltage detector 23 is sampled by the A / D converter and converted into digital data Dv, and the CPU stores the digital data Di and Dv in the storage unit 24.

  The storage unit 24 includes, for example, a semiconductor memory such as a RAM or an HDD (Hard disk drive). The output unit 25 is configured by a display device such as an LCD as an example, and displays the resistance value R of the measurement target 100 calculated by the processing unit 14 on the screen. It is also possible to employ a configuration in which the output unit 25 is configured by an external interface circuit, a radio circuit, or the like, and the resistance value R calculated by the processing unit 14 is transmitted to an external device.

  Next, the operation of the frequency detection device 3 will be described with reference to the drawings together with the operation of the insulation resistance measurement device 1. It is assumed that the probes PL1 and PL2 are connected in advance to the pair of portions P1 and P2 where the resistance value (insulation resistance value) R in the measurement target 100 is to be measured.

  In this state, when the power is turned on as shown in FIG. 3 (when supply of the AC voltage Vac to the power supply circuit 2 is started), the power supply circuit 2 starts generating the DC voltage Vdc. Thereby, each component which comprises the insulation resistance measuring apparatus 1 starts operation | movement. Further, power supply noise Sn is generated from the power supply circuit 2 with the start of supply of the AC voltage Vac to the power supply circuit 2.

  As shown in FIG. 3, the frequency detection device 3 starts outputting the binarized signal S2 as soon as the operation starts. Specifically, in the frequency detection device 3, the antenna 11 receives the power supply noise Sn and outputs the detection signal S <b> 1 to the binarization circuit 13 through the filter circuit 12. At this time, high frequency components such as switching noise components included in the detection signal S1 are removed by the filter circuit 12. Further, the binarization circuit 13 converts the detection signal S1 into a binarization signal S2 having the same frequency as the detection signal S1 (that is, the same frequency as the frequency f of the AC voltage Vac) and outputs the binarized signal S2 to the processing unit 14.

  As shown in FIG. 3, the processing unit 14 functions as a component that constitutes a part of the frequency detection device 3 as soon as the operation is started, and executes a frequency detection process. In this frequency detection process, the processing unit 14 inputs the binarized signal S2 from the frequency detection device 3, and measures the period T of the binarized signal S2. For example, the processing unit 14 synchronizes with an internal reference clock (a clock that is sufficiently shorter than the cycle T), and then from the time when the binarized signal S2 shifts from the low level to the high level, then from the low level to the high level. The number of reference clocks (the number included in one period T) up to the time of shifting to the level is counted, and the period T is measured by multiplying this count value by the time of one period of the reference clock. In this case, the process part 14 can also employ | adopt the structure which measures the period T for several minutes, and measures these averages as the last period T. FIG.

  Note that in an AC voltage having a commercial frequency such as the AC voltage Vac, the frequency f is either 50 Hz or 60 Hz. Therefore, the period T corresponding to the frequency f of the AC voltage Vac is either one of 20 ms when the frequency f is 50 Hz and 16.7 ms when the frequency f is 60 Hz. Accordingly, a reference clock count value (first count value) at a time of 20 ms and a reference clock count value (second count value) at a time of 16.7 ms are respectively calculated in advance, and the first count value is calculated. The count value range having a margin above and below (a margin considering the variation in the frequency of the AC voltage Vac) is defined as a first count range for detecting 20 ms and stored in the storage unit 24 in advance. The storage unit 24 defines the range of the count value with margins above and below the second count value as the second count range for detecting 16.7 ms (the upper limit value is less than the lower limit value of the first count value). In advance. Then, the processing unit 14 compares the count value obtained by counting as described above with the first count range and the second count range stored in the storage unit 24, and the count value is the first count. When it is included in the range, it is measured that the cycle of the AC voltage Vac is 20 ms (that is, the frequency f is 50 Hz), and when the count value is included in the second count range, the cycle of the AC voltage Vac is 16.7 ms. It is also possible to employ a configuration for measuring that the frequency f is 60 Hz.

  This configuration will be described with a specific example. When the period of the reference clock is 200 μs, the first count value is 100 and the second count value is 83.5. Therefore, by providing a margin above and below each count value, for example, the first count range is defined as 91 to 124 and the second count range is defined as 71 to 90. Therefore, when the count value is included in the first count range, the processing unit 14 measures that the cycle of the AC voltage Vac is 20 ms (that is, the frequency f is 50 Hz), and the count value falls within the second count range. When included, it can be measured that the cycle of the AC voltage Vac is 16.7 ms (that is, the frequency f is 60 Hz).

  Further, the processing unit 14 causes the storage unit 24 to store at least one of the measured period T and the frequency f (= 1 / T) calculated based on the period T as a value indicating the frequency of the AC voltage Vac. Thereby, the frequency detection process is completed.

  Thereafter, the processing unit 14 repeatedly determines whether or not a measurement start instruction (not shown) output from the measurement start switch is input when an operation is performed on a measurement start switch (not shown) provided in the insulation resistance measuring apparatus 1. To detect.

  As illustrated in FIG. 3, the processing unit 14 functions as a component that constitutes a part of the resistance measurement circuit 4 and executes arithmetic processing when detecting the input of the measurement start instruction. In this calculation process, the processing unit 14 first executes an output start process for starting the output of the DC voltage Vo to the voltage output unit 21 of the resistance measurement circuit 4. As a result, the voltage output unit 21 starts to output the DC voltage Vo (DC voltage whose voltage value is defined as the test voltage value) between the pair of probes PL1 and PL2.

  In this case, the voltage output unit 21 increases the voltage value of the DC voltage Vo from the initial 0 volt to the test voltage value within a predetermined time t1, and maintains the test voltage value after reaching the test voltage value. . As a result, the DC voltage Vo of the test voltage value is supplied between the pair of parts P1 and P2 of the measurement object 100, and a current (DC current) is generated between the pair of parts P1 and P2 due to the supply of the DC voltage Vo. Ii flows.

  In the resistance measurement circuit 4, the current detection unit 22 detects this current Ii and outputs a voltage signal Si to the processing unit 14. Further, the voltage detection unit 23 detects the voltage Vi generated between the pair of parts P1 and P2 and outputs the voltage signal Sv to the processing unit 14. The processing unit 14 continuously converts the input voltage signal Si into the digital data Di, and continuously converts the input voltage signal Sv into the digital data Dv.

  Further, as shown in FIG. 3, the processing unit 14 converts the converted digital data Di, when a predetermined time t1 elapses from the time when the output of the DC voltage Vo is started to the voltage output unit 21. Dv is acquired (data is acquired) by the number (predetermined number) included in one cycle T (= 1 / f) measured in the frequency detection process, and stored in the storage unit 24.

  The processing unit 14 executes a calculation process of the resistance value R and an output process of the calculated resistance value R to the output unit 25 after the completion of the data acquisition. When calculating the resistance value R, the processing unit 14 first calculates the current value of the current Ii. In this case, the processing unit 14 calculates the average value “Dave” for the digital data Di for one period T stored in the storage unit 24, and calculates the current value of the current Ii based on the calculated average value “Dave”.

  The power supply noise Sn is superimposed on the current Ii and the voltage Vi. Since the voltage Vi is a high voltage such as DC 1000 V with respect to the voltage Vi, for example, even if the power noise Sn of about several mV is superimposed, it can be ignored. However, since the current value of the current Ii is extremely small, the influence of the superimposed power supply noise Sn cannot be ignored. Therefore, the waveform of the power supply noise Sn is the same sine wave as that of the AC voltage Vac, and the sine wave has a feature that the average value for one cycle of the sampling value becomes zero. In this example, the processing unit 14 uses the characteristics of this sine wave to calculate the average value “Dave” of the digital data Di affected by the superimposed power supply noise Sn as described above. The influence of Sn is eliminated.

  Next, the processing unit 14 calculates a voltage value of the voltage Vi. As described above, since the influence of the superimposed power supply noise Sn can be ignored for the voltage Vi, that is, the digital data Dv for one cycle T stored in the storage unit 24 has almost the same value, so the processing unit 14 Calculates the voltage value of the voltage Vi based on any one of the digital data Dv. For the digital data Dv, the influence of the power source noise Sn may be eliminated by calculating the average value Dvave in the same manner as for the digital data Di.

  Subsequently, the processing unit 14 calculates a resistance value (insulation resistance value) R between the pair of parts P1 and P2 of the measurement target 100 based on the calculated current value of the current Ii and the voltage value of the voltage Vi. And stored in the storage unit 24. In addition, the processing unit 14 outputs the calculated resistance value R to the output unit 25 to display the resistance value R on the screen.

  Finally, as illustrated in FIG. 3, the processing unit 14 performs output stop processing for stopping the output of the DC voltage Vo for the voltage output unit 21 of the resistance measurement circuit 4. As a result, the voltage output unit 21 stops the output of the DC voltage Vo between the pair of probes PL1 and PL2. Thereby, the arithmetic processing is completed, and the measurement of the resistance value R by the insulation resistance measuring device 1 is completed.

  Further, in the insulation resistance measuring apparatus 1 of this example, the processing unit 14 executes the frequency detection process immediately after the power is turned on to obtain the frequency f (or period T) of the AC voltage Vac, and the obtained frequency f A configuration in which (or period T) is used in arithmetic processing is adopted. Therefore, the time required to execute this arithmetic processing is mainly a predetermined time (waiting time) t1 for waiting for the DC voltage Vo to rise to the test voltage value, and 1 of the AC voltage Vac for data acquisition. It becomes almost equal to the total time with the time for the period.

  In addition to these times, the time required for the calculation of the resistance value R and the output to the output unit 25 and the time required for the control for starting and stopping the output of the AC voltage Vac to the voltage output unit 21 are also required. However, these times are the operating times of the hardware such as the processing unit 14 and are extremely short compared to the waiting time t1 and the time of one cycle of the AC voltage Vac. Therefore, as described above, the time required to execute this arithmetic processing can be considered to be substantially equal to the total time of the waiting time t1 and the time of one cycle of the AC voltage Vac.

  Therefore, in the insulation resistance measuring apparatus 1 of this example, at any test voltage value, 20 ms sufficient for the DC voltage Vo to surely rise to this test voltage value is secured for the waiting time t1. (In FIG. 3, as an example, the waiting time t1 is indicated by about 15 ms, which is longer than the time during which the DC voltage Vo rises to the test voltage value), and one cycle T of the AC voltage Vac for data acquisition Even if the minute time is longer than 16.7 ms and 20 ms, the resistance value R can be calculated and displayed on the output unit 25 within 50 ms at the latest from the start of the arithmetic processing.

  As described above, in the frequency detection device 3, the power supply noise (hum noise) Sn caused by the AC voltage Vac is received by the antenna 11, and the detection signal S 1 output from the antenna 11 is binarized by the binarization circuit 13. The signal is converted into S2, and the processing unit 14 detects the frequency of the AC voltage Vac based on the binarized signal S2.

  Therefore, according to the frequency detection device 3, the low voltage of the binarization circuit 13 and the processing unit 14 (low voltage such as + 5V which is a lower voltage than the AC voltage Vac which is the commercial voltage (AC100V)). Therefore, the electronic component includes an electronic component to which an AC voltage Vac that is a high voltage is applied and an electronic component to which a low voltage is applied. Unlike conventional frequency detection devices that use photocouplers to connect in an insulated state, the insulation distance is much shorter than the insulation distance that must be secured for electronic components and wiring patterns to which AC voltage Vac is applied. Thus, all electronic components and wiring patterns can be arranged on the circuit board. Thereby, according to this frequency detection apparatus 3, an apparatus can be reduced in size significantly. In addition, electronic components to which the alternating voltage Vac is applied (high-voltage electronic components) and photocouplers are generally expensive, but according to the frequency detection device 3, such electronic components can be made unnecessary. Product costs can also be reduced.

  Further, according to the insulation resistance measuring apparatus 1, the insulation resistance measuring apparatus 1 can be easily downsized by providing the frequency detecting device 3 that can be downsized as described above. Moreover, according to this insulation resistance measuring device 1, the product cost of the insulation resistance measuring device 1 can be reduced by providing the frequency detection device 3 capable of reducing the product cost as described above.

  In the above example, the insulation resistance measurement device 1 is described as an example of a measurement device to which the frequency detection device 3 is applied. However, the measurement device is not limited to the insulation resistance measurement device 1, and from the measurement target. The frequency detection device 3 can be applied to various measurement devices in which the acquired measurement target signal is affected by the power supply noise Sn.

  In the above example, the frequency detection device 3 is input to the power supply circuit 2 based on the power supply noise Sn emitted from the power supply circuit 2 built in the insulation resistance measurement device 1 together with the frequency detection device 3. The frequency f (or period T) of the AC voltage Vac is detected, and the frequency detection device 3 includes an antenna 11, a filter circuit 12, a binarization circuit 13, a processing unit 14, a storage unit 24, and an output unit 25. It is configured as an independent device (a device not incorporated in another device), and configured to detect the frequency f (or period T) of the AC voltage Vac input to any other device. You can also

DESCRIPTION OF SYMBOLS 1 Insulation resistance measuring apparatus 2 Power supply circuit 3 Frequency detection apparatus 11 Antenna 13 Binarization circuit 14 Processing part Di Digital data Ii Current Ii
R Resistance value S1 Detection signal S2 Binary signal Sn Power supply noise Vac AC voltage

Claims (2)

An antenna for receiving a power supply noise having the same frequency as the power supply frequency of the AC voltage generated from a power supply circuit to which the AC voltage is input and outputting a detection signal having a waveform similar to the waveform of the AC power supply;
A binarization circuit that binarizes the detection signal and outputs the binarized signal;
A frequency detection apparatus comprising: a processing unit that executes a frequency detection process for detecting the power supply frequency by detecting a frequency of the binarized signal. A frequency detection device according to claim 1;
An A / D converter that samples a measurement target signal acquired from the measurement target and converts the signal into digital data;
A calculation unit that executes a calculation process for calculating the parameter to be measured based on a predetermined number of the digital data;
The said calculating part is a measuring apparatus which prescribes | regulates the said number for the said calculation process based on the said power supply frequency detected by the said frequency detection apparatus.

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