I have a half-bridge strain gage sensor (pre-assembled product) with a 30cm cable, which I am trying to interface with my PCB containing a 24-bit ADC.
The connector at the cable end toward the ADC (i.e., the end away from the strain gage) has the following four pins, based on my reading of the resistances:
- Pin 1: V_Excitation
- Pin 2: Doesn't seem to be connected to anything
- Pin 3: V_signal
- Pin 4: Ground
All good so far.
However, in addition, there is the metallic shield constituting the body of the connector.
Being new to strain gages and ADC measurements, I am unsure of the shield's significance -- I presume it has something to do with minimizing interference-based offsets. (Also, I don't want to break open the cable to see what's inside but I'm guessing it is a standard twisted-pair cable.)
Question A: What role exactly does the shield play in a strain gage / ADC application?
Question B: And thus which of the following is good practice to follow with the shield? :
- Just isolate shield from GND (i.e., leave shield alone) ?
- Or connect shield directly to the Ground plane on my ADC pcb ?
- Or place 4.7 nF Capacitor and 1M resistor between shield and Ground, as suggested for USB connector shield in this question ?
- Or connect shield to metal chassis of my enclosure only, as suggested in this question ?