JPH0518706Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a level measuring device for measuring the level of an input signal.

BACKGROUND ART In order to expand the measurement range, level measuring instruments have conventionally been used in which an input signal is attenuated by an attenuator before being detected, and the attenuation amount is added to the detected level.

FIG. 1 shows a conventional level measuring device of this type.

In Fig. 1, 1 is a variable attenuator that attenuates the input signal, 2 is a detector that detects the output signal of the variable attenuator 1, and 3 is an A/D that converts the analog signal output from the detector 2 into a digital signal. Converter; 4 is an attenuator driver that provides the variable attenuator 1 with a control signal for varying the amount of attenuation so that the output level of the A/D converter 3 falls within a predetermined range; 5 is an attenuator driver for the A/D converter 3; A computing unit that adds the output signal and the amount of attenuation output by the attenuator driver 4; 6 is a display driver that drives the display 7; 7 is a display that receives the output of the display driver 6 and displays visible numbers. be.

In this conventional device, an input signal is attenuated by a variable attenuator 1, then detected by a detector 2, and an analog signal, which is the detection output, is converted into a digital signal by an A/D converter 3. The output signal of this A/D converter is output to the arithmetic unit 5 and the attenuator driver 4. When the attenuator driver 4 receives the output signal from the A/D converter, it increases or decreases the reference attenuation amount and sends a control signal to the variable attenuator 1 so that the level falls within a predetermined range. As a result, the amount of attenuation by the variable attenuator 1 is increased or decreased so that it increases when the level of the input signal is high, and decreases when the level of the input signal is low.
The output signal of the A/D converter 3 and the signal representing the amount of attenuation output from the attenuator driver 4 are
This value is displayed by the display driver 6 as a visible number on the display 7 as an input signal. Therefore, in this device, even if the input signal level differs, the attenuation amount is automatically adjusted according to the fluctuation of the input level, and the input signal level is determined from the detected output level and the attenuation amount of the attenuator. This has the advantage that the input signal level can be accurately measured over a wide range.

However, this device had the following disadvantages.

That is, when the level of the input signal becomes small and therefore the level of the output signal of the A/D converter 3 becomes small, the signal from the A/D converter 3 sent to the attenuator driver 4 becomes smaller.
The amount of attenuation of the variable attenuator 1 controlled by the output signal of is also reduced. Even if the amount of attenuation becomes zero and the level of the input signal becomes even smaller than a certain value, the level of the output signal of the A/D converter 3 will be lower than the noise level generated from the A/D converter 3 itself. Must not be. Therefore, even if the level of the input signal becomes smaller than a certain value, the output level of the A/D converter 3 does not become smaller.
Since the level of the input signal is calculated and output based on the amount of attenuation from the input signal, an erroneous value will be displayed on the display 7 due to the noise level.

It is an object of the present invention to overcome these drawbacks and provide a level measuring device that makes it possible to distinguish between correct and incorrect addition outputs of the arithmetic unit 5.

To this end, in the present invention, if the output value of the A/D converter is below a level within a predetermined range and the attenuation amount of the attenuator is zero, the output value of the calculator is determined to be incorrect. It is characterized by providing a means of warning.

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 2 shows an embodiment of the level measuring device of the present invention.

In this embodiment, a variable attenuator 1, a detector 2,
A/D converter 3, attenuator driver 4, computing unit 5,
The display driver 6 and display 7 are the same as those shown in FIG.

8 is a first comparator that detects whether the output level of the A/D converter 3 is below the noise level and outputs a detection signal if it is below the noise level, and 9 is an attenuator driver 4. This is a second comparator that outputs whether the output value representing the amount of attenuation of is zero or not, and outputs a detection signal when it is zero. 10 is a detector that outputs an alarm signal when it detects that the detection signals from the first and second comparators 8 and 9 are output simultaneously, and 11 generates an alarm display based on the alarm signal of the detector 10. This is an alarm driver that blanks the display on the display 7. 12
is an alarm indicator which displays an alarm by lighting a lamp or by sounding an alarm in response to the output signal of the alarm driver 11. Note that the upper limit of the level range output by the A/D converter can be set to a level slightly lower than the saturation level, and the lower limit can be set to a level slightly higher than the noise level.

In the level setter configured as above, the A/D
If the information converted into a signal by the converter 3 is below the noise level and the signal representing the amount of attenuation output from the attenuator driver 4 is zero, the first and second comparators 8 and 9 simultaneously output detection signals. is output, an alarm signal is output from the detector 10, which drives the alarm driver 9, and the alarm display 10 visually or sounds to notify the operator. Furthermore, the alarm driver 11 can also blank the display 6 through the display driver 5. In this way, it is possible to identify whether the measurement level is correct or incorrect.

Similarly, when the variable attenuator 1 is set manually, it is possible to distinguish between correct and incorrect settings. Further, 1 may be an amplifier.

In the embodiment shown in FIG. 2, a case is illustrated in which a combination of single elements is used, but as in the embodiment shown in FIG.
The output value of the A/D converter 3 and the variable attenuator 1 described above
It is also possible to realize correct/incorrect identification by providing software processing with a function of calculating the attenuation amount of the A/D converter 3 and detecting that the output of the A/D converter 3 is below the noise level and the attenuation amount is zero, and issuing an alarm.

As explained above, according to the present invention, it is possible to identify whether a level value is correct or incorrect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional level measuring device, and FIGS. 2 and 3 are block diagrams showing an embodiment of the present invention. 1...Variable attenuator, 2...Detector, 3...A/
D converter, 4... Attenuator driver, 5... Arithmetic unit, 6... Display driver, 7... Display device, 8, 9...
... Comparator, 10 ... Detector, 11 ... Alarm driver, 12 ... Display device, 13 ... Microprocessor.

Claims (1)

[Claims for Utility Model Registration] An attenuator that attenuates an input signal, a detector that detects an output signal of the attenuator, and an A/D converter that converts the output signal of the detector into a digital signal;
an attenuator driver that controls the amount of attenuation of the attenuator so that the output signal of the A/D converter has a level within a predetermined range, and outputs the value of the attenuation amount;
a computing unit that computes the level of the input signal from the output signal of the A/D converter and the value of the attenuation amount output by the attenuator driver; and a computing unit that computes the level of the input signal based on the output signal of the computing unit. In the level measuring device, the level measuring device includes: an alarm that outputs an alarm signal when the output signal of the A/D converter is less than the level of the predetermined range and the amount of attenuation of the attenuator is zero; A level measuring device characterized by being provided with means.