Interference has destructive damage to the flow transmitter, today we will talk about how the transmitter in the signal transmission to do anti-interference, all-round protection of the normal and effective operation of the transmitter.

　There are three ways to transmit transmitter signals against interference:

　Method 1: photocoupling isolation measures

Transmitter signals in the long-distance transmission process, the use of photocoupler, can control system and input channel, output channel circuit cut off contact. The external spike interference signal will not enter the transmitter through the system, to avoid the harm of interference.

Photocoupling advantage is that it can effectively suppress the spike pulse and various noise interference, so that the signal-to-noise ratio of the flow transmitter signal transmission process is greatly improved. Interference noise although there is a large voltage amplitude, but the energy is very small, can only form a weak current, and photocoupler input part of the light-emitting diode is in the current state of operation, the general conduction current of 10mA ~ 15mA, so even if there is a very large amount of interference, this kind of interference will be suppressed due to the inability to provide sufficient current.

Method 2: Twisted shielded wire transmission

Transmitter signals in the transmission process will also be affected by electric field, magnetic field and ground impedance and other interference factors, level transmitter using grounded shielded wire can reduce the interference of electric field. Twisted-pair cable compared with coaxial cable, although the frequency band is poor, but the anti-common-mode noise ability is strong, can make the various small links of electromagnetic induction interference to offset each other. In addition, the transmitter in the long-distance transmission process, generally using differential signal transmission, can improve the anti-interference performance.

Transmitters use twisted shielded cable to transmit signals, which can effectively suppress periodic interference, spike pulse and interference between devices.

　Method 3: Elimination of locally generated errors

Level transmitters in low-level measurements, for in the signal path used in (or composed of) the material must be given strict attention, in simple circuits encountered in the solder, wire, as well as terminals and so on may produce the actual thermal potential. Since they often occur in pairs, it is an effective measure to try to keep these pairs of thermocouples at the same temperature.