JP3248663B2 - Frequency measuring instrument - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency measuring device for measuring the frequency of a noise voltage by storing the number of peaks of an electromagnetic noise voltage waveform within a predetermined time and calculating the reciprocal of the number of peaks. Things.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional typical frequency measuring instrument F.
It is a block diagram which shows C2.

In the frequency measuring device FC2, an amplifying circuit 51 amplifies the amplitude of an AC signal to be measured, a waveform shaping circuit 52 shapes the waveform into a pulse, and an AC signal output from a reference oscillator 53 is divided by a frequency dividing circuit. The frequency is divided by 1 and the gate control circuit 55 generates a gate control signal based on the frequency-divided signal.

The gate circuit 56 allows the output pulse of the waveform shaping circuit 52 to pass for a predetermined time in the gate control signal, and the counting circuit 57 counts the passed pulse.
The arithmetic circuit 58 converts the number of counted pulses into a frequency, and uses the converted value as a frequency output.

The reference oscillator 53, the frequency dividing circuit 54, the gate control circuit 55, the gate circuit 56, the counting circuit 57, the arithmetic circuit 58 and the like are controlled by a control circuit 59 and perform cooperative operations.

[0006]

Since the conventional frequency measuring device FC2 uses a waveform shaping circuit for shaping an input signal into a waveform and converting it into a pulse, the circuit configuration of the entire frequency measuring device is complicated. However, there is a problem that the entire frequency measuring device is expensive.

In the conventional frequency measuring device FC2, the number of pulses is measured within the gate signal time, so that the accuracy of the frequency measurement is determined by the accuracy of the reference oscillator 53 which affects the gate time. In order to obtain a highly accurate measurement result, it is necessary that the reference oscillator 53 has high accuracy and high stability. Therefore, there is a problem that the reference oscillator 53 is expensive and the entire frequency measuring device becomes expensive.

An object of the present invention is to provide a frequency measuring device for measuring the frequency of electromagnetic noise which has a simple circuit configuration and is inexpensive.

[0009]

According to the present invention, a rectifier circuit and an integrating circuit having a simple circuit configuration are used instead of a circuit for shaping a waveform of an input signal used in a conventional frequency measuring instrument and converting it into a pulse. It was done.

[0010]

According to the present invention, a rectifier circuit and an integrating circuit are used instead of a circuit for shaping an input signal into a waveform and converting it into a pulse, so that the circuit configuration is simplified and a frequency measuring device for measuring the frequency of electromagnetic noise. Becomes cheaper.

[0011]

FIG. 1 is a block diagram of a frequency measuring device CF1 according to an embodiment of the present invention.

The frequency measuring device CF1 is a measuring device for detecting the voltage of electromagnetic noise transmitted through a communication line, a power line or the like by using a current probe or a high impedance probe. Part 20;
The control unit 40 includes a frequency display unit 30 and a control unit 40.
Controls the frequency measurement unit 20 and the frequency display unit 30.

FIG. 2 is a block diagram showing the frequency measuring section 20 in the above embodiment.

The frequency measuring unit 20 includes a rectifying circuit 21 for suppressing the amplitude of the detected electromagnetic noise to one half, and a signal output by the rectifying circuit 21 which is higher than the frequency of the electromagnetic noise to be measured. An integration circuit 22 for suppressing a high-frequency signal of a predetermined frequency or more; a peak count circuit 23 for counting the number of peaks of a signal output by the integration circuit 22 within a predetermined time; A storage circuit 24 for storing the number n of peaks counted in the Nth time (N is an integer of 2 or more) each time, and the number n of a plurality of peaks stored in the storage circuit 24 is determined by majority decision. An arithmetic circuit 25 for calculating the frequency of the electromagnetic noise to be detected based on the determined number of peaks and the predetermined time; a peak count circuit 23;
4 and a control circuit 26 for controlling the arithmetic circuit 25.

Since the number n of peaks determined by the majority decision is a number generated in a predetermined time, the arithmetic circuit 25 converts this number into a number per second and calculates the reciprocal of the converted number. It is a circuit that calculates and determines that the calculated value is the frequency of the electromagnetic noise to be detected. Further, the control circuit 26 controls the peak count circuit 23, the storage circuit 24, and the arithmetic circuit 25 with a clock signal, and the predetermined time is set based on the clock signal.

Next, the operation of the above embodiment will be described.

FIG. 3 is a diagram showing a state after the detected electromagnetic noise is rectified in the above embodiment.

First, as shown in FIG. 3, the electromagnetic noise voltage detected by the electromagnetic noise voltage detector 10 has its negative side electromagnetic noise suppressed by the rectifier circuit 21.

FIG. 4 is a diagram showing a state after the specified high-frequency electromagnetic noise is suppressed by the integration circuit 22 in the above embodiment.

A time constant circuit such as a CR circuit is provided in the integrating circuit 22, and the value of the harmonic component to be removed is determined according to the time constant set by the time constant circuit (measurement of this time constant). Can be adjusted arbitrarily). Therefore, the integration circuit 22 has a function of removing a harmonic component having a predetermined frequency or higher, and FIG. 4 shows a noise voltage in which high-frequency noise having a frequency higher than a specified frequency is suppressed.

FIG. 5 is an explanatory diagram of the operation in which the peak count circuit 23 counts the number n of peaks within a predetermined time in the above embodiment.

The peak count circuit 3 counts the number of peaks of the signal output by the integrator circuit 22 within the first count time (predetermined time), and the counted peak number n is "6". FIG. 5 shows an example in which the number of peaks n counted by the peak count circuit 3 during the second count time (predetermined time) and the third count time (predetermined time) is “5” and “5”, respectively. It is. The count time (predetermined time) is set based on a clock signal output from the control circuit 26.

Thereafter, the number of peaks counted by the peak count circuit 23 for the first to third times as described above is stored in the storage circuit 24 each time, and a plurality of peaks stored in the storage circuit 24 are stored. The numbers "6", "5", "5"
The majority is determined, and therefore “5” is determined as the number n of peaks. Based on the determined number of peaks “5” and the predetermined time, the arithmetic circuit 25 determines the frequency of the electromagnetic noise to be detected. Calculate. That is, since the number of peaks “5” determined by majority vote is the number generated in the predetermined time,
This number is converted to the number of peaks per second, the reciprocal of the converted number is calculated, and the calculated value is determined to be the frequency of the electromagnetic noise to be detected.

The number of peaks "6", "5", "5" stored in the storage circuit 24 is not determined by majority, but the number of peaks "6", "5", The number n of peaks may be determined based on the median value of “5”.

FIG. 6 is a flowchart showing the operation of the above embodiment.

First, a rectifier circuit 21 suppresses a half of the amplitude of the detected electromagnetic noise, and among the signals output from the rectifier circuit 21, a signal having a frequency equal to or higher than a predetermined frequency higher than the frequency of the electromagnetic noise to be measured. After the high frequency signal is suppressed by the integration circuit 22, the peak count circuit 23 counts the number n of peaks of the signal output by the integration circuit 22 within a predetermined time (S
1) The storage circuit 24 stores the number of peaks counted by the peak count circuit 23 from the first time to the Nth time (N is an integer of 2 or more) each time (S2). Predetermined number N
Only when the peak number n is stored (S3), the storage circuit 24
The arithmetic circuit 25 determines the number of the plurality of peaks stored in the memory as a majority or a median (S4). Based on the determined number of peaks and the predetermined time, the frequency of the electromagnetic noise to be detected is determined. Is calculated by the arithmetic circuit 25 (S5). Then, the calculated frequency is displayed on the frequency display section 30 (S6).

In the above embodiment, a rectifying circuit and an integrating circuit are used instead of a circuit for shaping a waveform of an input signal which is conventionally used and converting it to a pulse. A frequency measuring device for measuring the frequency of the electromagnetic noise becomes inexpensive.

Further, in the above embodiment, the clock signal of the control circuit is used instead of the expensive reference oscillator and its auxiliary circuit which are required to have high accuracy and high stability, which are conventionally used. The structure of the vessel is simplified and the economy is excellent.

In the above embodiment, the rectifier circuit 21
A logarithmic amplifier may be added to the preceding stage, whereby the level of the electromagnetic noise input to the rectifier circuit 21 is made uniform, and the reliability of the measured frequency is improved.

[0030]

According to the first aspect of the present invention, a rectifying circuit and an integrating circuit are used in place of a circuit for shaping a waveform of an input signal and converting the signal into a pulse, which has been conventionally used. And the frequency measuring device for measuring the frequency of the electromagnetic noise becomes inexpensive.

According to the second aspect of the present invention, an expensive reference oscillator which is required to have high accuracy and high stability and an auxiliary circuit therefor, which are conventionally used, are not required, so that the configuration of the frequency measuring device is simplified. And has an effect that the economy is excellent.

According to the third aspect of the present invention, the level of the electromagnetic noise input to the rectifier circuit is made uniform, and the reliability of the measured frequency is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a frequency measuring device CF1 according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a frequency measuring unit 20 in the embodiment.

FIG. 3 is a waveform diagram showing a state after rectification of detected electromagnetic noise in the embodiment.

FIG. 4 is a diagram showing a state after a specified high-frequency electromagnetic noise is suppressed by an integrating circuit in the embodiment.

FIG. 5 is an explanatory diagram of an operation in which the peak count circuit counts the number n of peaks within a predetermined time in the embodiment.

FIG. 6 is a flowchart showing the operation of the embodiment.

FIG. 7 is a block diagram showing a conventional typical frequency measuring device FC2.

[Explanation of symbols]

 FC1: frequency measuring device, 10: electromagnetic noise voltage detecting unit, 20: frequency measuring unit, 21: rectifying circuit, 22: integrating circuit, 23: peak count circuit, 24: storage circuit, 25: arithmetic circuit, 26: control circuit , 30 ... frequency display unit, 40 ... control unit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-274471 (JP, A) JP-A-52-139475 (JP, A) JP-A-4-268467 (JP, A) JP-A-2- 285269 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 23/10 G01R 29/00

Claims (3)

(57) [Claims] 1. A measuring instrument for detecting a voltage of electromagnetic noise transmitted through a communication line or a power line using a current probe or a high impedance probe, wherein the rectifier circuit suppresses a half of the amplitude of the detected electromagnetic noise. And an integration circuit for suppressing a high-frequency signal of a predetermined frequency or more higher than the frequency of the electromagnetic noise to be measured among the signals output by the rectifier circuit; and a peak of a signal output within a predetermined time by the integration circuit. Peak counting means for counting the number; this peak counting means is first to
Storage means for storing the number of peaks counted in the N-th time (N is an integer of 2 or more) each time; and determining the number of the plurality of peaks stored in the storage means by majority or median, Calculating means for calculating the frequency of the electromagnetic noise to be detected based on the determined number of peaks and the predetermined time. 2. The frequency measuring device according to claim 1, wherein the predetermined time is set based on a clock signal of a control circuit for controlling each of the circuits or each means. 3. The frequency measuring device according to claim 1, wherein a logarithmic amplifier is added to a stage preceding the rectifier circuit.