JPH0274888A - Ultrasonic wave detector - Google Patents

Abstract

PURPOSE:To detect even a body to be detected at a detecting limit stably by adjusting the amplitude in a circuit in correspondence with the magnitude of a signal because the magnitude of the reflected wave signal from a reflecting body is increased and decreased in correspondence with the relative humidity of air. CONSTITUTION:The tip of a reflecting body 9 which is provided in a protruding pattern from the front surface of a case 1 is positioned in front of an ultrasonic wave piezoelectric transducer 2. An A/D converter 10 and an amplitude correcting means 8 constituted with a CPU are provided in a detecting circuit which is housed in the case 1. The reflected wave from the reflecting body 9 is found by a signal which is received with the ultrasonic wave piezoelectric transducer 2 after a preset specified time is elapsed from the time when the ultrasonic wave has been transmitted from the ultrasonic wave piezoelectric transducer 2. Since the reflected wave from the reflecting body 9 is changed with the humidity of air, amplitude is corrected with the amplitude correcting means 8 so that the amplitude is increased when the received signal of the reflected wave from the reflecting body 9 becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic detection device that uses ultrasonic waves emitted from an ultrasonic transducer to confirm the presence or absence of an object to be detected and to measure the distance.

(Prior art) Fig. 3 is a block circuit diagram of a conventional ultrasonic detection device, in which an ultrasonic transducer 2 provided on the front of a case 1 is composed of a piezoelectric element, etc., and converts electrical signals into mechanical amplitude and This is a transducer that exchanges mechanical amplitude into an electrical signal.This ultrasonic transducer 2 is driven by a drive circuit 3 in a case 1 to emit ultrasonic waves, which hit an object to be detected and are reflected. The reflected wave returns to the ultrasonic transducer 2. Here, it is converted into an electric signal, amplified by an amplifier circuit 4, passed through a comparator 5, and then enters a distance measuring means 6 consisting of a CPU, from wave transmission to wave reception. The circuit has a circuit configuration that determines whether or not there is an object to be detected within a predetermined area by measuring the elapsed time.

[Problem to be solved by the invention]

In the above-mentioned conventional ultrasonic detection device, since the received signal obtained is a reflected wave, it is inevitably small, so to compensate for this, an amplification circuit 4 having a constant amplification factor is provided. However, the size of the object to be detected (area of the reflective surface)
may not necessarily be large enough to be detected.

This includes not only the size of the detected object itself but also the size of the effective reflection area depending on the position of the detected object. When this size is a detectable claw tool, it is largely affected by the condition of the air, which is the medium of ultrasonic waves. For example, the relative humidity of the air changes the attenuation rate of the sound, making it undetectable. There is. In other words, there is a problem in that the size of the detectable object varies depending on changes in humidity. As a countermeasure to this, there is a method of equipping the ultrasonic detection device with a humidity sensor and using this to process and correct the received signal, but this makes the ultrasonic detection device expensive and reduces its value as a practical product. lose.

In view of the above-mentioned circumstances, an object of the present invention is to provide an ultrasonic detection device that corrects the attenuation rate of sound due to the relative humidity of the air in an inexpensive manner and can stably detect objects to be detected that are at the detection limit. It is about providing.

[Means to solve the problem]

In this invention, the sound attenuation rate due to the relative humidity of the air is corrected by the following method. In other words, an ultrasonic transducer is provided on the front of the case, a detection circuit is housed inside the case, and the ultrasonic transducer intermittently emits ultrasonic pulses until the reflected waves return to the ultrasonic transducer. In ultrasonic detection devices that measure time and distance to detected objects, a reflector is installed in front of the ultrasonic transducer attached to the front of the case, and an analog/digital converter is installed in the detection circuit built into the case. An amplification factor correction means comprised of a CPU and a CPU was added, and the amplification factor was corrected based on the reflected wave from the reflector.

[For production]

Since the reflected wave from the reflector provided in front of the ultrasonic transducer changes depending on the humidity of the air, the amplification factor correction means compares the received signal due to the reflected wave with a plurality of set values to reduce the received signal. If so, increase the amplification factor.

〔Example〕

Fig. 1 is a block circuit diagram of an ultrasonic detection device according to an embodiment of the present invention, and Fig. 2 is a perspective view of the same device, in which the same parts as those shown in Fig. 3 are given the same symbols and explained. is omitted. This embodiment differs from conventional ultrasonic detection devices in that the tip of a reflector 9 protruding from the front surface of the case 1 is located in front of the ultrasonic transducer 2, and the detection circuit built into the case 1 Analog/digital converter 10 and C
This is the addition of an amplification factor correction means 8 constituted by a PU.

In such a configuration, the reflected wave by the reflector 9 can be known from the signal received by the ultrasonic transducer 2 after a predetermined period of time has passed since the ultrasonic transducer 2 emits an ultrasonic wave. can. Furthermore, since the reflected wave from the reflector 9 changes depending on the humidity of the air (for example, the higher the humidity, the smaller the reflected wave becomes), the amplification factor correction means 8 uses the amplification factor when the reflected wave reception signal from the reflector 9 becomes smaller. is corrected to make it higher.

〔Effect of the invention〕

In this invention, since the magnitude of the reflected wave signal from the reflector increases or decreases depending on the relative humidity of the air, the attenuation factor can be corrected by adjusting the degree of amplification in the circuit according to the magnitude of this signal. Even objects to be detected that are at the detection limit can be detected stably against changes in humidity. Note that the only additional parts are the reflector and the analog/digital converter, and the amplification factor correction means simply adds a software function to the conventional CPU, and the parts are essentially the same, so it is inexpensive. Depending on the configuration, it is possible to provide an ultrasonic detection device that can perform stable detection.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of an ultrasonic detection device according to an embodiment of the present invention, FIG. 2 is a perspective view of the same device, and FIG. 3 is a block circuit diagram of a conventional ultrasonic detection device. 1: Case, 2: Ultrasonic transducer, 8: Amplification factor correction means,
9: Reflector, 10: Analog/digital converter.

Claims (1)

[Claims] 1) An ultrasonic transducer is provided on the front of the case, a detection circuit is housed inside the case, and the ultrasonic transducer intermittently emits ultrasonic pulses until the reflected waves return to the ultrasonic transducer. In an ultrasonic detection device that measures the distance to the detected object by measuring the time of What is claimed is: 1. An ultrasonic detection device comprising: an amplification factor correcting means constituted by a reflector and a CPU; and the amplification factor is corrected based on a reflected wave from a reflector.