An intelligent 4~20ma two-wire photoelectric level transmitter

Abstract

The invention relates to an intelligent 4-20mA two-wire photoelectric level transmitter, which is characterized in that it includes a processor, a power conversion circuit connected to the processor, a photoelectric sensor control detection unit, a DA converter and a HART communication unit ; Among them, the processor controls the acquisition of the photoelectric sensor and controls the detection unit to obtain the liquid level signal. The liquid level signal is converted into a 4-20mA standard signal through the DA converter, and the 4-20mA carrier through the HART communication unit complies with the Bell202 international standard protocol. Realize two-way digital communication between transmitter and control room. It has the advantages of low power consumption, wide power supply range, super error correction capability for sensor data, high stability and reliability, and reduced maintenance intensity of on-site personnel.

Description

technical field [0001] The invention relates to an intelligent 4-20mA two-wire photoelectric level transmitter. Background technique [0002] Steel strip level gauges are widely used in the measurement of oil storage tanks, and infrared photoelectric sensors are used to detect liquid levels in steel strip level gauges. At present, in the field automation information management and control system, the application of 4-20mA signal has been generally recognized, and more and more steel strip level gauges with 4-20mA output have been widely used. However, due to the limitations of the processing circuit of the photoelectric liquid level transmitter currently in use, the transmitter generally adopts a three-wire system, two of which are power supplies, and one is a 4-20mA signal output. The working conditions of this circuit are relatively high and There are many disadvantages and deficiencies: In places where there are intrinsically safe explosion-proof requirements, it is very...

AI Technical Summary

Problems solved by technology

However, due to the limitations of the processing circuit of the photoelectric liquid level transmitter currently in use, the transmitter generally adopts a three-wire system, two of which are power supplies, and one is a 4-20mA signal output. The working conditions of this circuit are relatively high and There are many shortcomings and deficiencies: In the use places with intrinsically safe explosion-proof requirements, because the transmitter requires high power supply voltage and large working current, it is very difficult to select a safety barrier; the three-wire working mode of the transmitter will also cause on-site engineering The increase of cable cost; the transmitter has no carrier HART digital interface in the form of 4-20mA three-wire output, and the two-way data transmission with the control room cannot be realized, and the maintenance of the instrument is difficult; the key part of the infrared photoelectric sensor for liquid level detection of the transmitter The logic processing of the ordinary gate circuit is adopted, and the data error rate is high; the long-term working aging of the infrared photoelectric sensor of the transmitter changes the transmission characteristics, and the increase of the matching deviation causes the working stability to decrease; the gray code band of the sensing liquid level is made Strict process requirements, high production costs, and high intensity of on-site operation and maintenance

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