Application Notes

EAP-032144

Surge Protector for Use of 4-wire RTD

We make a temperature measurement of high precision with 4-wire RTD sensor.

Since we know M-System universal type transmitter, model M3LU is applicable to 4-wire RTD sensor, we use this model for the measurement. We also like to install a lightning surge protector but can not find a suitable one for 4-wire RTD.

I’m aware that M-System lightning surge protector, model MDP-RB is used for 3-wire RTD but can we protect 4-wire RTD line with multiple units of the MDP-RB?

Yes, the MDP-RB is applicable. If you want to protect both RTD end and the M3LU end, please use 4 pieces of the MDP-RB. Please refer the connection method of following figure 1. You need to install 2 pieces of MDP-RB for each end and then connect each unit terminal #2 and #3 with each other in order to limit overvoltage, which possibly occur between 2 pieces of MDP-RB.