Noise Filtering for RTDs
Shielded twisted cable and a simple capacitor filter removes most noise from RTD signals
Noise pickup by the RTD cables can sometimes be a problem. A small amount of voltage noise pickup is reflected in a noise in the temperature reading, with ±10μV noise causing as much as a ±0.1°C reading-to-reading temperature variation when using a 3-wire RTD.
The first line of defense against noise pickup is proper cabling. The RTD wires should be connected through shielded cable containing a twisted pair for the RTD element wires.
Much of the remaining measurement noise can be removed by filtering at the Wildcard input using 10μF ceramic capacitors, as shown in the following circuit schematic. The capacitors should be ceramic rather than electrolytic.
Noise pickup by the RTDs can be greatly reduced by placing 10μF ceramic capacitors.
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