Industrial production often use transmitters, such as pressure transmitters, temperature transmitters, liquid level transmitters, etc., but the standard signal of these transmitter class is clear? Pressure transmitter class standard signal transmission why is 4 ~ 20mA, rather than 0 ~ 20mA?

80 ghz radar level transmitter is the main circuit current to be measured in a linear proportion, converted to DC 4 ~ 20mA constant current loop standard signal output device. The main circuit can be AC or DC. At the receiving end through a 250Ω (or 500Ω) resistor, and then convert the DC DC4~20mA current signal to DC DC1~5V (or 2~10V) voltage signal for meter display or computer processing.

The benefits of using DC4~20mA for the output current.

        1, some transmitters can be powered by the receiving end of the two-wire system, the operating current of 4mA or less is sufficient, so the quiescent current is set at 4mA. if the DC0 ~ 20mA standard, it will not be possible to achieve the two-wire power supply.

        2, the transmitter by the receiving end of the two-wire power supply, can improve the anti-interference ability, improve the signal-to-noise ratio, improve the accuracy of current signal transmission. Constant current output is not affected by line resistance and can be transmitted over longer distances.

        3, through the 4mA static current monitoring, you can determine whether the constant current loop has a broken line fault. If the receiving end does not monitor the 4mA current, it means that the loop may have a broken line or poor contact fault. 0 ~ 20mA output, because the static current is 0 when normal, disconnection is also 0, it is impossible to determine whether normal or disconnected.

        4, the transmitter output quiescent current is not 0, and will not cause trouble. At the receiving end either smart display meter, or computer, to remove this static value is very easy, can be achieved by hardware, but also by software, software implementation is more simple, just do a subtraction.

        5, 4 ~ 20mA linear constant current output, is one of the standard output interface parameters of the transmitter. In addition to current transmitters, many analog output transmitters, such as ip65 pressure transmitter, also use 4 ~ 20mA constant current output, of course, there are also voltage output type.

The above is the introduction of "commonly used transmitter standard output signal", if you want to know more level switch (level switch, level switch), level meter (level meter, level meter) and other level measuring instrument knowledge, welcome to pay attention to and contact us!