Ultrasonic detector


Ultrasonic transmitter transmits ultrasonic waves in a certain direction, starting timing at the same time, ultrasonic waves propagating in air, immediately returning to the obstacle on the way, returning immediately, ultrasonic reception When the reflection wave is received, it stops immediately. The speed of the ultrasonic wave is 340 m / s. According to the time t records in the timer, the distance (S) of the emission point is the obstacle (S), ie: S = 340T / 2. This is the so-called time difference measurement method.

The principle of ultrasonic ranging is known that the propagation speed of ultrasonic waves in air is known, and the measurement sound waves encountered the time when the obstacle reflects back, calculates the launch point according to the time difference of transmitting and reception. The actual distance of the obstacle. It can be seen that the principle of ultrasonic ranging is the same as the radar principle. The ranging formula is expressed as: L = C × T

formula L is the measured distance length; C is the propagation speed of ultrasonic waves in air; T is the time difference of measurement distance propagation (T is transmitted to The received time value is half).

Ultrasonic ranging is mainly applied to the distance measurement of reversing reminders, construction sites, industrial scenes, etc., although the current ranging range can reach 100 meters, but the accuracy of the measurement can only reach the centimeter level. Since the ultrasonic wave is easy to oriented, the direction is good, the strength is easy to control, and the advantage that the object does not require direct contact, is an ideal means for the liquid height measurement. In the precision level measurement, it is necessary to reach a millimeter measurement accuracy, but the current domestic ultrasonic ranging dedicated integrated circuit is only a centimeter level measurement accuracy. By analyzing the cause of the ultrasonic ranging error, improve the measurement time difference to the microsecond level, and after the compensation of the sound wave propagation speed with the LM92 temperature sensor, we design the high-precision ultrasonic ranging instrument to reach millimeters measurement accuracy.


Different from its structure and installation method, one is to install two ultrasonic transducers within the same housing, that is, received, and Type, its working principle is based on the Sonic Doppler effect, also known as Doppler type. The energy field distribution of the ultrasonic waves of the emitted ultrasonic wave has a certain direction, typically, the directional area is elliptical. The other is to place the two transducers in different locations, that is, a dispenser, referred to as a sound field type detector, and its transmitter and receiver use non-directional (ie, full-direction) Transducer or semi-directed transducer. The non-directional transducer produces a hemispherical energy field distribution mode, and the semi-directional generating a tapered energy field distribution mode.

Received, the unselected ultrasonic detector is large, can control hundreds of cubic meters of space, multiple sets of use can be alerted to a larger space.

Installing the space sealing requirements of the ultrasonic detector is high, there should be no large capacity air flow, and there is no too much doors and windows and need to be closed. The flow of ventilation and gas should be avoided. The spatial sound insulation protection protected by ultrasonic detector is good to reduce the false positives caused by external noise. Ultrasonic waves have no penetration to the object, so avoiding the shielding of the object, glass, separator, and door, etc. should be poor when used, so it should not be installed. Ultrasonic is air as a transmission medium, so the temperature and relative humidity of air can affect its detection sensitivity. When the temperature is 21 ° C, when the relative humidity is 38%, the attenuation of ultrasonic waves is most severe, and the detection range is also minimized.

Switching alarm

Switched alarm is controlling the circuit through the closure and disconnection of various types of switches, thereby triggering alarm. Common switches include a magnetron switch, a micro switch, a pressure pad, or a variety of type switches that use wires, metal strips, metal foils, etc.

The magnetron switch is also known as the magnetron or the reed switch, composed of permanent magnets and reed. The magnetron switch should avoid being mounted directly on the metal object, and the steel door special type of magnetron switch or changes to the microswitch or other type of switching device should be used when used.

Pre-type ultrasonic detector

Traditional integrated ultrasonic detector is installed above each parking space, so that the drawback is an indicator of integrated detector. Easy to be blocked by the parking lot. The front ultrasonic parking detector is used, the detector integration indicator is installed directly above the parking space, avoiding the case where the indicator is blocked.

The unique ultrasonic emission probe in the ultrasonic emission module of the front ultrasonic parking space detector makes the detection more stable, and the success rate is as high as 99.9%. The emission probe in the middle of the ultrasonic emission probe and the overall angle of the super-wave reception probe are optimally angled in the overall angle of the horizontal surface, and solve the problem of detecting the unstable windshield signal due to individual vehicles.

Because the detector is different from traditional design, it is effective to reduce the equipment cost and construction cost of the parking space, and effectively reduce construction time.


Ultrasonic detector records the bus people's traffic

Ultrasonic detection The device recorded the bus man traffic is a device that automatically records the traffic of the bus at each time of each site. The device is composed of a sensor and signal processing circuit, and the sensor is ultrasonic detector 1, the ultrasonic detector. The output end of the ultrasonic transmitter 11 and the ultrasonic receiver 12, the output end of the ultrasonic receiver 12, the output terminal of the module / digital converter 21, the digital signal processor 22, the digital signal processor 22 The output termination signal processor 31, the signal processor 31 also interfaces with the memory 32, the transmit receiver 33, and the ultrasonic detector 1 is mounted at the door frame of the door, and the ultrasonic transmitter 11 is mounted on the other side. Installing the ultrasonic receiver 12, the "RXD, TXD" end of the microcontroller IC1 in the signal processor 31 also contacts the card read signal line of the bus IC card reader 34.

Ultrasonic detector Application design of Underground Parking lot For the problem of parking in large parking lot, the parking lot boot system is used for the speed of the ultrasonic ranging from the principle of ultrasonic ranging. Algorithm, based on single-chip microcomputer and RS-485, the control program is written. This shows the rest of the parking lot in real time, and the parking population will quickly find the purpose of the parking space.

Water Near Ultrasonic Detector Emission Signal Circuit Design

Water Near Ultrasonic Detector for Deep Missing Proximity Targets and Detonation. Brere frequency offset detection principle, the detector consists of a transmitter, a conversion circuit, a receiver, and a signal processing circuit. The transmit signal is the key to the design. The clock generating circuit uses a 1MHz crystal oscillator to generate a 500 kHz ultrasonic pulse; Division control The circuit is a pulse signal having a filling frequency at 500 kHz. After synchronous detection, it becomes a pliable frequency frequency, as a filling pulse signal; the transmit signal circuit considers the matching of the water hearing, using a two-transmit tube parallel structure. Such high frequency The non-cycle narrow pulse signal has the advantages of high frequency, small energy consumption, short wavelength, small diffraction, good direction, and small radiographer, and is particularly suitable for application to deep bomb composite.

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