Transmitters convert electrical analog signals
In many applications controlled by single-chip microcomputer, transmitters are used to convert signals that cannot be directly measured by single-chip microcomputers into electrical analog signals that single-chip microcomputers can process, such as current transmitters, pressure transmitters, temperature transmitters, flow changers transmitter, etc.
Most of the early transmitters are of voltage output type, that is, the measurement signal is converted into 0-5V voltage output, the signal power is less than 0.05W, and the digital signal is converted by the analog/digital conversion circuit for the microcontroller to read and control. However, when the signal needs to be transmitted over a long distance or the grid interference is large in the use environment, the use of the voltage output sensor is greatly limited, exposing the shortcomings of poor anti-interference ability, line loss destroying the accuracy, etc., and the two Wire current output transmitters are widely used because of their extremely high anti-interference ability.
The anti-interference ability of the voltage output type transmitter is extremely poor, the damage of the line loss is not to mention how high the accuracy is, and sometimes the output DC voltage is superimposed with AC components, which makes the single-chip microcomputer produce misjudgments, control errors, and in serious cases It will damage the equipment. The output 0-5V must not be transmitted remotely. After the remote transmission, the line voltage drop will be large, and the accuracy will be greatly reduced. Now many ADC, PLC, DCS input signal ports are made into two-wire current output type transmitter 4-20mA, which proves the inevitable trend of voltage output type transmitter being eliminated.