JPH06273452A - Digital sampling-type measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a measuring apparatus which can find the effective value or the mean-value rectification of repetitive waveforms up to a high frequency. CONSTITUTION:An apparatus is provided with a sample-and-hold circuit 30 which samples and holds the input signal of repetitive waveforms in synchronization with a sampling clock fs, with an A/D converter 40 which converts the output of the sample-andhold circuit 30 into a digital signal and with an operation device 70 which operates the output of the A/D converter 40. In the apparatus, a plurality of sampling clock generators 51, 52 which generate sampling clocks are installed, and one out of the plurality of sampling clock generators is selected and changed over in such a way that the frequency (f) of the input signal and the sampling clock fs do not have a relationship of f+(1/2).fs.n (where n=1, 2, 3,...) when a mark + is used as a symbol representing proportion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device for obtaining an effective value or average value rectification of a repetitive input waveform by a digital sampling method.

[0002]

2. Description of the Related Art A conventional example of this type of measuring device is shown in FIG. In the figure, 1 is a terminal to which an input signal having a repetitive waveform is applied, 2 is a sample and hold circuit, 3 is an analog / digital converter (hereinafter referred to as A / D converter), 4 is a sampling clock generator, Reference numeral 5 is an effective value calculator for obtaining an effective value of an input signal, and 6 is an output terminal.

In the apparatus having such a configuration, the repetitive waveform applied to the input terminal 1 is sampled and held in the sample and hold circuit 2 in synchronization with the sampling clock obtained from the sampling clock generator 4. At the same time, it is added to the A / D converter 3 and converted into a digital signal. The converted digital signal is added to the calculator 5 to perform an effective value calculation, and the calculation result is taken out from the output terminal 6.

In such a device, assuming that the frequency of the input signal applied to the terminal 1 is f and the frequency of the sampling clock obtained from the sampling clock generator 4 is fs, as already known. , F and fs
Has a relationship of f ◇ (1/2) · fs · n (n = 1, 2, 3, ...) (1), there is a problem that a correct calculation result cannot be obtained. The symbol ⋄ indicates "proportional".

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to obtain a measuring device capable of obtaining the effective value of a repetitive waveform up to a high frequency.

[0006]

The present invention is a sampling /
A sample and hold circuit that samples and holds an input signal having a repetitive waveform in synchronization with the clock fs, and an A that converts the output of this sample and hold circuit into a digital signal.
In a device including an A / D converter and an arithmetic unit that calculates the output of the A / D converter, a plurality of sampling clock generators that generate the sampling clocks are provided, and a frequency f of an input signal is generated. And sampling clock f
The plurality of sampling clock generators are selectively switched so that s does not have a relationship of f ◇ (1/2) · fs · n (n = 1, 2, 3, ...). .

[0007]

According to the present invention as described above, by selecting one of the plurality of sampling clock generators, the relationship between the frequency f of the input signal and the sampling clock fs does not become the above relationship. You can do it.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The device of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram showing an embodiment of the device of the present invention.
In the figure, 10 is a terminal to which a repetitive waveform of frequency f is applied as an input, 20 is an input circuit for converting the input applied from the terminal 10 into a signal of an appropriate level, 30 is a sample and hold circuit, and 40 is A. / D converter, 51, 52
Is a sampling clock generator for generating sampling clocks of frequencies fs1 and fs2, 60 is a switching circuit, 70 is an effective value calculator (digital signal processor) for obtaining the effective value of the input repetitive waveform, and 80 is It is a microprocessor (hereinafter referred to as CPU).

The switching circuit 60 switches between the sampling clock generators 51 and 52 and is controlled by the CPU 80. The output of the sampling clock generator 51 or 52 that has passed through the switching circuit 60 is used as a sampling clock by the sample and hold circuit 30 and the A /
It is provided to the D converter 40. 90 is a display, CPU8
The effective value of the input signal obtained by the arithmetic unit 70 is displayed under the control of 0. 100 is a frequency measuring circuit, the input terminal of which is connected to the terminal 10 to detect the frequency of the input signal. The detection signal is sent to the CPU 80. The operation of the apparatus having such a configuration will be described based on the flowchart shown in FIG.

Assuming that the frequency of the repetitive waveform input applied from the terminal 10 is f, the input signal of this frequency f is given to the sample and hold circuit 30, and the frequency is detected by the frequency measuring circuit 100. Are taken into the CPU 80. The CPU 80 uses this frequency f
Then, it is determined whether or not the sampling clocks fs1 and fs2 output by the sampling clock generators 51 and 52 have the relationship represented by the equation (1). fs1 is (1)
If there is no relation of expression, the sampling clock generator 51 is selected through the switching circuit 60 under the control of the CPU 80, and the sampling clock of the frequency fs1 is given to the sample and hold circuit 30 and the A / D converter 40. The input signal is sampled and held in synchronization with the clock and converted into a digital signal. This digital signal is subjected to effective value calculation in the calculator 70, and the calculation result is C
It is displayed on the display 90 under the control of the PU 80.

When the frequency f of the input signal and the sampling clock fs1 have a relationship represented by the equation (1), C
The PU 80 judges this and sends a switching signal to the switching circuit 60, switches the sampling clock generator 51 to 52, and supplies the sampling clock fs2 to the sample and hold circuit 30 and the A / D converter 40. As a result, the input signal is sampled at the clock fs2 and converted into a digital signal. The converted digital signal is subjected to effective value calculation by the calculator 70, and the value is displayed on the display 90.

As described above, according to the present invention, a sampling clock for generating sampling clocks having different frequencies is used.
Since a plurality of clock generators are provided and the sampling clock is switched according to the frequency of the input signal, it is possible to obtain an effective value up to an input signal of a high frequency at a low sampling frequency with respect to the repeated input waveform. For example, when the frequency of the first sampling clock is 20 KHz and the frequency of the second sampling clock is 19 KHz, the frequency at which the effective value cannot be correctly calculated according to the equation (1) is 190 KHz × n (n =
1, 2, 3, ...), and the effective value can be measured for a repetitive input waveform up to near 190 KHz.

In the above embodiment, the effective value measurement is explained. However, if the arithmetic unit 70 having the function of obtaining the average value rectification is used in the apparatus of FIG. 1, the apparatus of FIG. The average value rectification type measuring device can be used.

[0014]

According to the present invention, it is possible to obtain an apparatus capable of measuring the effective value or average value rectification of a high frequency input waveform.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of a measuring apparatus according to the present invention.

FIG. 2 is a flowchart for explaining the operation of the measuring device according to the present invention.

FIG. 3 is a circuit configuration diagram of an example of a conventional measuring device.

[Explanation of symbols]

 30 sample and hold circuit 40 A / D converter 51, 52 sampling clock generator 60 switching circuit 70 arithmetic unit 80 microprocessor 90 display unit 100 frequency measurement circuit

Claims (2)

[Claims] 1. A sample and hold circuit for sampling and holding an input signal having a repetitive waveform in synchronization with a sampling clock fs, an A / D converter for converting an output of the sample and hold circuit into a digital signal, and the A /
In a device provided with an arithmetic unit for obtaining an effective value of an input signal from the output of a D converter, a plurality of sampling clock generators for generating the sample clock are provided, and a symbol ⋄ is used as a symbol representing proportionality. In this case, the plurality of sampling clock generators are arranged so that the frequency f of the input signal and the sampling clock fs are not in the relationship of f ◇ (1/2) .fs.n (n = 1, 2, 3, ...) Digital sampling type measuring device that is selectively switched. 2. A sample and hold circuit for sampling and holding an input signal having a repetitive waveform in synchronization with a sampling clock fs, an A / D converter for converting the output of the sample and hold circuit into a digital signal, and the A / D converter. /
In a device equipped with an arithmetic unit for obtaining an average value of a rectified waveform diagram of an input signal from the output of a D converter,
When a plurality of sampling clock generators for generating a clock are provided and the symbol ⋄ is used as a symbol representing proportionality, the frequency f of the input signal and the sampling clock fs are f ◇ (1/2) ・ fs ・ n (n = 1, 2, 3, ...) A digital sampling type measuring device in which the plurality of sampling clock generators are selectively switched so that the relationship of (1, 2, 3, ...) Is not established.