The application of signal isolator in the wiring of non-electric analog sensors

The isolation mode is divided into: optical isolation, which has the function of isolation, distribution equipment, transformation, dispatch and alarm identification, and the input to output of the isolator has 2000VAC voltage resistance level between the four ends of the switching power supply to the ground. Its characteristics are transformer isolation: stable characteristics, long life, strong load working capacity, high isolation compressive strength, but the power circuit is complex, processing technology requirements are higher, such as EW series product signal isolator; Optical isolation: smooth characteristics, strong anti-interference, simple route, cheap cost, service life and isolation compressive strength slightly low transformer isolation, such as BETIC series product signal isolator; These two kinds of isolation signal isolators have been widely used in many hydropower plant projects in recent years. They reasonably deal with the isolation of switching power supply and analog data signals in the automatic control system and sensor work of the detection system in the natural environment of the hydropower plant, resist the damage of DC interference signals and lightning overvoltage, and ensure the measurement accuracy of the sensor and the smooth and reliable operation of the system optimization.

The volume is slightly larger than the basic wiring terminal, and the sliding rail can be assembled. The input/output is on a different side from the switching power supply terminal, and the short circuit fault is reasonably avoided. At this stage, the most widely used and feasible wiring methods are: The output control circuit of the DC24V switching power supply in the control cabinet is connected to the switching power supply terminal of the signal isolator through the special terminal in the screen to supply the switching power supply of the isolator in operation. The 1 pair input data signal terminal of the isolator is connected to the 2-wire sensor (and contains the DC24V switching power supply). A pair of output data signal terminals of the isolator output 4 ~ 20mA analog output and connect to the input terminal of the in-screen analog control module. For the 3-wire sensor, the isolator 3-wire input data signal terminal is connected to the sensor (with DC24V+, public end (DC24V-) and pulse signal input), and the isolator 1 pair of output data signal terminal output 4 ~ 20mA analog is connected to the in-screen analog control module input terminal. For the 4-wire sensor, the isolator can not show the isolated DC24V switching power supply, generally use the control cabinet switching power supply to show a separate DC24V switching power supply, the sensor output 4 ~ 20mA analog data signal connected to the isolator data signal input terminal. A pair of output data signal terminals of the isolator output 4 ~ 20mA analog output and connect to the input terminal of the in-screen analog control module. The upper 2 and 3 wire sensor can perform reasonable isolation of switching power supply and analog data signal input in sensor work according to the isolator in the control cabinet, and the 4 wire sensor can perform reasonable isolation of analog data signal input according to the isolator in the control cabinet. The signal isolator can complete the isolation of the digital power amplifier analog on the spot of the hydropower plant (the sensor itself has a working switching power supply, output 4 ~ 20mA analog) and the microwave sensor analog (the sensor needs to show the switching power supply in the work and form the input/output home with the data signal output). Because of the signal isolator's high toughness isolation, distribution equipment, conversion, dispatch and alarm identification function, it reasonably ensures the stable operation of the switching power supply and analog quantity collection control module in the control cabinet, prevents the possibility of mold penetration or damage, improves the measurement accuracy, and reduces the damage of DC interference signals and lightning overvoltage.

In view of the limitations of the installation standards for non-power consumption sensors on the spot in some power plants, the analog output data signal needs to be expanded to process a 4 ~ 20mA analog data signal and transmit it to two different control and detection systems. For example, the working pressure at the inlet of the vortex shell, the working pressure at the inlet of the tail water pipe, the pulsating beverage at the inlet of the tail water pipe, the working pressure of the cover, and the purification head of the generator set are provided to the electronic computer video surveillance system of the plant, and to the application of the generator set condition detection system. Some of its individual 4 ~ 20mA power consumption analog needs to expand 2-3 4 ~ 20mA output can be used to expand the signal isolator, that is, 1 4 ~ 20mA power consumption and non-power consumption analog input, output 2 or 3 4 ~ 20mA analog through the isolator, It reasonably completes the requirements of power plant operation and detection of different separate system software, reduces project investment, simplifies secondary wiring, and solves the problems caused by on-site sensor installation in power plants.