Errors related to cable resistance imbalance in three-wire RTDs can be minimized.
Many sources of error exist in process applications, and they can impact the accuracy of a resistance temperature detector (RTD) measurement. The cable incorporated into the sensor can cause a significant error.
This article presents an analysis of cable resistance imbalance in three-wire RTDs, with emphasis on the errors that affect the accuracy of the temperature measurement. Guidance and techniques are given for minimizing the magnitude of these errors.
RTDs are temperature sensors that use the predictable change in electrical resistance of a material (typically, platinum) with changing temperature. To provide a practical temperature measuring instrument for process applications, it is necessary to attach extension leads to the platinum sensing element. If not properly selected for the application, the number and type of extension leads used can introduce significant errors into the temperature measurement (figure 1).