JPH0441313B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a distance measuring device that can test the operation of a transducer while measuring it.

(Background Art) A conventional device is shown in FIG. In Figure 1, 1
is a timing generation circuit, 2 is a pulse oscillator, 3 is an amplifier, 4 is a transducer switch, 5 is a transducer, 6
is in the air, 7 is the reflector, 8 is the base, 9 is the amplifier,
10 is a shaping circuit, 11 is a flip-flop, 12
is an AND gate, 13 is a counter, and 14 is an oscillator. This device operates as follows. First, a timing pulse is generated by a timing generation circuit 1, and a pulse oscillator 2 is caused to oscillate a pulse at a transmission frequency. This pulse is amplified by an amplifier 3 and then sent to a transducer 5 via a transmitter/receiver switch 4.
The electrical signal is converted into an ultrasonic signal by the transducer 5 and sent into the air 6. This ultrasonic signal propagates through the air 6, is reflected by a reflector 7, propagates through the air 6 again, is received by the transducer 5, and is converted into an electric signal again. It passes through the transmitter/receiver switch 4 and is amplified to a certain level by the amplifier 9.
Sent to 0. The shaping circuit 10 sends out a pulse when a signal exceeding a certain threshold value is received, and sends out a pulse when a received signal exceeds a certain level. The flip-flop circuit 11 is set by the timing pulse of the timing oscillator 2 and reset by the received pulse. In other words, the Q-side output of the flip-flop 11 remains "1" only during the period from transmission to reception. This signal and the clock of oscillator 14 are connected by AND gate 12.
AND is taken and the counter 13 measures it. now,
The time from transmission to reception is T (S), the propagation speed is C (m/s), and the distance from the transducer to the reflector is L (m).
Then, L=1/2CT. Here, C can be considered to be a proportionality constant that depends on the frequency of the oscillator 14, so the frequency is determined so that L can be directly read.

This circuit has a drawback in that it is difficult to determine the difference between the case where there is no reflector 7 and the case where the transducer 5 fails because there is no difference. Although the base portion 8 is a reflector, since it is outside the directivity of the transducer 5, it cannot provide a reception level sufficient to activate the shaping circuit 10.

(Problem to be solved by the invention) The distance measuring device of the present invention transmits an ultrasonic pulse signal toward a reflector using a transducer, receives the pulse signal reflected by the reflector, and receives a predetermined first pulse signal. Amplification is performed by an amplifier set to the amplification degree, and the time from the time when the ultrasonic pulse signal is sent out by the transducer to the time when the level of the output signal of the amplifier exceeds a predetermined first threshold is measured. , a distance from the transducer to the reflector is measured based on the time, and means for setting a test timing period of a predetermined length within a period in which the distance to the reflector is being measured; , during the test timing period, changing the amplification degree of the amplifier from a first amplification degree to a second amplification degree higher than the first amplification degree, or setting a threshold value for detecting the level of the output signal of the amplifier; The present invention is characterized by comprising: means for changing the first threshold value to a second threshold value lower than the first threshold value.

(Example) FIG. 2 shows an example of the present invention. Here 1-8
and 10 to 14 have the same names as in FIG. 1 and have similar functions. Reference numeral 9' denotes a variable amplification type amplifier, the amplification degree of which is variable by an amplification control circuit 16. 15 is a binary counter,
16 is an amplification control circuit. Next, the operation of the above configuration will be explained. The binary counter 15 simply counts the timing signal of the timing generator 1. The amplification control circuit 16 sets the amplification of the variable amplification type amplifier 9' for distance measurement until the count value of the binary counter 15 reaches a predetermined first count value. Thereby, the variable amplification type amplifier 9' amplifies the signal input from the transducer 5 using the first amplification degree set at the time of distance measurement, and sends it to the shaping circuit 10. The shaping circuit 10 detects the level of the output signal of the variable amplification type amplifier 9' using a predetermined first threshold value. Thereafter, the circuit operates in the same manner as the conventional circuit described with reference to FIG.

Thereafter, after the count value of the binary counter 15 reaches a predetermined first count value, the first count value is
During the test timing period until the second count value becomes larger than the count value of Switching to a second amplification degree (>first amplification degree) for the test timing period. Next, the variable amplification type amplifier 9' amplifies and transmits the signal inputted from the transmitter/receiver 5 via the transmitter/receiver switch 4 according to the second amplification degree.

Therefore, the amplification control circuit 16 controls the period set by the counter value of the binary counter 15,
That is, from the first count value to the second count value, the amplification degree of the variable amplification type amplifier 9' is set for test measurement. For example, such a period may correspond to 1 count out of 30 counts of binary counter 15, i.e. timing generator 1.
One cycle out of 30 cycles of the timing signal may be set for testing.

When the output signal of the variable gain amplifier 9' exceeds a first threshold, the shaping circuit 10 sets its output to a level that activates the reset input R of the flip-flop 11.

Furthermore, when the count value of the binary counter 15 exceeds the second count value, the amplification degree control circuit 16
Then, the amplification degree of the variable amplification type amplifier 9' is returned to the first amplification degree, and the distance measuring device operates in the same manner as when measuring the distance described above. As a result, the flip-flop 11 is reset and the carry signal of the counter 13 is no longer output, so that it can be detected that the transducer system is operating normally.

As explained above, in the first embodiment, even if there is no target reflector during the test, the amplification of the receiving section can be increased and the transmission/reception system can be tested using reflections from the foundation. Malfunctions can be detected early.

In the first embodiment, a binary counter is used to operate the test circuit, but it is not necessary; even if the test timing is generated by a circuit incorporating a binary counter in the timing generator 1, the same effect can be obtained. will occur. It is also possible to use a switch instead of a binary counter and to perform the test when the switch is on.

Further, instead of increasing the amplification degree, a second threshold value lower than the first threshold value of the shaping circuit may be set at the time of testing, and a similar effect can be obtained.

(Effects of the Invention) Since the present invention has a test circuit, it has the advantage of being able to easily discover failures, and can be used in ultrasonic distance measuring devices such as water level gauges and depth sounders.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional distance measuring device, and FIG. 2 is a block diagram of a first embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Timing generation circuit, 2... Pulse oscillator, 3... Amplifier, 4... Transducer/receiver switch, 5...
...Transducer/receiver, 6...Air, 7...Reflector, 8...
Basic part, 9... Amplifier, 9'... Variable amplification type amplifier, 10... Shaping circuit, 11... Flip-flop, 12... AND gate, 13... Counter,
14...Oscillator, 15...Binary counter, 16...Amplification control circuit.

Claims (1)

[Claims] 1. A transducer transmits an ultrasonic pulse signal toward a reflector, receives the pulse signal reflected by the reflector, and sets a predetermined first amplification degree. Amplify with an amplifier, and measure the time from the time when the ultrasonic pulse signal is sent out by the transducer to the time when the level of the output signal of the amplifier exceeds a predetermined first threshold, and based on the time, In a distance measuring device for measuring the distance from the transducer to the reflector, means 1 for setting a test timing period of a predetermined length within a period in which the distance to the reflector is being measured;
11, 15, during the test timing period, changing the amplification degree of the amplifier from the first amplification degree to a second amplification degree higher than the first amplification degree, and detecting the level of the output signal of the amplifier. and means 9', 10, 16 for causing any one of changing the threshold value from the first threshold value to a second threshold value lower than the first threshold value. measuring device.