The wiring of Displacement sensor with analog input module

In order to reduce the electromagnetic interference displacement sensor, transmit analog signals should be used when the twisted pair shielded cable, cable shielding layer should be grounded on both ends. If there are points difference on both ends of the cable, cable shielding layer should be grounded. Generally what circumstance should be grounded on both ends, what circumstances should a little ground?

1: at the ends of the earth point because there is no potential difference, there are potential difference will be weak current, the shielding layer is actually turned into ground wire;

2: grounding on both ends of the shield work in high frequency interference is more serious to work site, due to shield and internal signal line is formed between capacitive coupling to the signal circuit, seriously will affect the signal miscalculation.

3: read all sorts of governor and PLC instructions are protestations of shielded wire must be single-end grounding and grounding line should end at the side of the controller.

Single side, both ends have defects:

A shielding layer of cable transmission is a fundamental measures to reduce electromagnetic interference. In the past, some design rules requirements: signal transmission cable shielding layer, should be in commonly grounding bus bar in the control room, should not be empty or repeated earthing. Namely USES the single-end grounding method, but this kind of defect of grounding method.

Transmission cable shielding layer only end do grounding and the other end of the suspension, it will only prevent electrostatic induction, not because of the magnetic field strength changes induced by the interference voltage. In order to reduce the induction voltage of shielding layer filling line, in some of the weak current equipment technical requirements shield only made under the condition of grounding connection at one end, and should adopt double shielded cable insulating material, its outer shield should at least do grounding connection at both ends. In this way, the outer shield and other equally do the grounding connection of a conductor loop, sensing a current, the resulting lower source magnetic field intensity magnetic flux, so as to offset basically have no outside the voltage induced in the shield.

Single side grounding that:

Shield anti-interference function principle, basic is like this: interference source and the receiving end of equivalent capacitance of the poles. There is voltage fluctuation by capacitance induction to the other side. Is inserted into the earthing of the middle layer (shield) destruction of the equivalent capacitance, thus cutting interference pathway.

And on both sides of the two grounding will cause potential, potential range will have a lot of current (in current loop) shielding function damage.