JPH0129586Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Technical field of the invention This invention is a method of monitoring and measuring input signal levels carried out in various communication methods, by measuring the input signal level as an effective value that is directly related to its power. (Root
Mean Square RMS value)
In particular, it relates to the configuration of an rms value conversion measurement circuit that accurately and quickly measures input signals with a large fluctuation range using rms to direct current conversion IC (integrated circuit) elements, which have recently become standard packages and have become popular.

(b) Prior art and problems In any communication system, measuring the signal level at each stage of the device is considered the most basic monitoring method, and a simple method is to simply rectify the signal voltage and find the average value. A method of monitoring is being adopted. However, if the signal waveform deviates from a constant waveform such as a sine wave, the average value cannot be easily converted to an effective value, so there is a need for a measurement circuit that directly displays the effective value of the signal level. To find the effective value, there are two methods: one is to perform the calculation of square → average → square root (square root) on the input signal according to the definition formula, and the other is to equivalently find the effective value using a thermoelectric element. Recently, circuits based on these two methods have been modularized and commercially available and can be easily used as circuit elements in devices. However, all of the circuits of the effective value converting element include a low-pass filter consisting of a resistor R and a capacitor C or a device equivalent thereto as an averaging circuit, and the converting circuit has time constant characteristics. Therefore, it takes time to establish the value of the DC output voltage of the effective value conversion element circuit with a certain degree of accuracy. This establishment time becomes longer as the input level to the conversion element is lower. There is also the problem that if the input level is too high, the conversion element will be saturated and the signal will be distorted.

(c) Purpose of the invention The purpose of the present invention is to provide a measuring circuit configuration that can accurately measure the effective value of a signal level whose input level fluctuates over a wide range in a short period of time.

(d) Structure of the invention In this invention, the circuit of the effective value conversion element has a parallel configuration of a high-level conversion circuit and a low-level conversion circuit,
The low-level conversion circuit is equipped with an amplifier before the conversion element to make the input level to the conversion element almost equal to the high-level conversion circuit, and the DC output voltages of both conversion circuits are alternately switched with a changeover switch to reach a common DC level. The circuit is configured such that the measurement is performed by the detection circuit, and the measured value is converted to a true value by the level conversion circuit according to the changeover switch.

(e) Embodiment of the invention An example of the configuration of an effective value conversion measurement circuit according to the invention will be described with reference to the drawings. FIG. 1 shows an example of a circuit of an arithmetic type effective value conversion element, which consists of a square circuit of 1, an averaging circuit of 2, and a square root circuit of 3, and the effective value of the input voltage εi is measured as the DC output voltage Eo. Since the averaging circuit 3 of the conversion element includes a time constant circuit of a resistor R and a capacitor C, it takes time for the DC output voltage Eo to establish a value with constant accuracy. Figure 2 shows the characteristics of one of the commercially available arithmetic type effective value conversion elements.The horizontal axis is the input level, and the vertical axis is the effective value establishment time, which is a multiple of 1 when the input is 1V. be. From the figure, the establishment time becomes constant when the input level is several hundred mV or more, but when the input level is several mV
It can be seen that the establishment time increases by a factor of 10 when the value decreases to .
FIG. 3 shows the configuration of a measuring circuit according to the present invention, in which 10 is a high level conversion circuit, 20 is a low level conversion circuit, each of which has an effective value conversion element 4. The low level conversion circuit 20 has an amplifier 5 in front of the conversion element 4. 6 is a changeover switch, 7 is a DC level detection circuit, and 8 is a level conversion circuit. In the figure, the AC signal input εin to be measured is applied to a parallel circuit of a high level conversion circuit 10 and a low level conversion circuit 20, and is converted into DC voltages Eh and El, respectively. The DC voltages Eh and El are alternately switched by a changeover switch 6 with a fast response speed and measured by a DC level detection circuit 7, but the measured DC value is converted into a true value by a level conversion circuit 8 according to the changeover switch 4. Ru. That is, the DC voltage Eh is output as is, but the DC voltage El is converted by the amplification degree of the amplifier 5 and output as the DC voltage Eout representing a correct effective value. Note that the input signal level to the high level conversion circuit 10 is adjusted to an appropriate level so as not to saturate within the circuit.

By configuring the measurement circuit as described above, the signal level applied to the conversion element 4 during measurement will be approximately the same high level both when the input signal is low level and when the input signal is high level. Measurement errors no longer need to be considered.

(f) Effects of the invention As detailed in the above embodiments, the invention has great effects because the effective value of an AC signal input whose input level fluctuates over a wide range can be accurately measured in a short time.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of the effective value conversion element, FIG. 2 is a measurement value establishment time, and FIG. 3 is a block diagram of the effective value conversion measurement circuit. In the figure, 1 is a squaring circuit, 2 is an averaging circuit,
3 is a square root circuit, 4 is an effective value conversion element, 5 is an amplifier, 6 is a changeover switch, 7 is a DC level detection circuit, and 8 is a level conversion circuit.

Claims (1)

[Scope of utility model registration request] In an effective value conversion measurement circuit that measures AC signals with level fluctuations using an effective value DC conversion element, the conversion element circuit is configured in parallel with a high level conversion circuit and a low level conversion circuit, and a low level conversion circuit is used. An amplifier is installed in front of the conversion element to make the input level to the conversion element approximately equal to the high level level, and the DC output voltages of both conversion circuits are alternately switched with a changeover switch and measured by a common DC level detection circuit. , an effective value conversion measurement circuit characterized in that a measured value is converted to a true value by a level conversion circuit according to a changeover switch.