The current through the PT100 resistance sensor will cause heating: for example, a sensing current of 1 mA through a 1000 ohm resistor will generate 1 mW heat. If the sensor element fails to dissipate this heat, the temperature value will be artificially bred. This effect can be reduced either by using a large sensor element or by ensuring that it is in thermal contact with its surroundings.
The use of a detection current of 1 mA will give a signal of only 1V. Because the change in resistance for one degree Celsius is very small, even a small error in measuring the voltage across the sensor will produce a large error when monitoring temperatures. For example, a voltage measurement error of 1mV will give an error of 0,4 ° C in the temperature reading. Likewise, a 10 μA error in the sense current will result in a temperature difference of 0,4°C.
Due to the low signal levels, it is important to keep cables away from electrical cables, motors, equipment and other devices that may emit electrical noise. Using a shielded cable with the screen grounded at one end can help reduce interference. When using long cables, it is necessary to check that the measuring equipment is able to withstand the resistance of the cables.