RTD circuit in industerial application

Question

I'm trying to design RTD measuring for industrial use which has EMI/EMC/ESD.
I have 3 wires input to the board.

obviously 3 wires out of the board are going to 3-wire configuration PT1000
1- 3V3 (RTD 1)
2- B (RTD 2)
3- B (RTD 3)

• Vout is going to MCU ADC
• in second image i attached you can see i have different resistor for op amp gain.

and what I'm thinking of is the following:
1- add capacitor for (B) before the (+) of LM358 to filter noise
2- add 3 TVS diodes to the 3 wires (to GND)
3- add current limiting 10k resistors before the RTD sensor (as shown below) 4- no 10k resistors but add PTC fuse on the 3v3 rail to the sensor to protect shorting?

Protection Questions:

• is protection with TVS is required actually?
• do you see any flaw or mistake in the circuit, any suggestion is welcomed.
• i don't know if industrial designers protect all inputs/outputs from applying certain level of voltage like +-24v? or it always depend on the project and i don't need to think about it here. so should i think about it here?

wheatstone Questions:

• every time the wire length (going to RTD) changes will need to change software compensation variable?
• as you can see I'm simulating the circuit but is't practically going to work efficiently?

Answer 1

The circuit seems flawed, as there is no well controlled voltage reference. Ti has a few good ADCs dedicated to RTD readback, but if you are using a MCU ADC a circuit like AN-1559 would be recommended.

TVS devices can be used, but they are a fairly large risk to the circuit accuracy due to leakage currents (you probably have to use higher stand-off ratings then expected). I think keeping the connections to the RTD higher impedance and clamping with low-leakage diodes is a good option, but it depends on what the external threat is.

For simulation you should do a resistance sweep instead of just transient analysis.

You probably won't have to worry much about wire-length, 3- and 4- wire help with that. But it doesn't seem critical if you are starting without RTD ADCs or very precise low-drift opamps.

It is always safe to assume that the wire-harness will be erroneously wired (I think 1-2 per 100 contacts is reasonable), so if there is 24V or whatever on the connector there should ideally be no permanent damage.