To test a 4-20 mA sensor, what is the recommended connection method?

The recommended connection method for testing a 4-20 mA sensor is in series. This is because 4-20 mA signals are designed to be transmitted through a continuous loop, which means that the sensor, the power supply, and the receiving device (like a controller or indicator) are all part of a single circuit.

By connecting the sensor in series, you can accurately measure the current flowing through the loop. This setup allows you to observe how the current changes in response to different conditions being sensed, which is critical for verifying the sensor's functionality and calibration. In a series connection, any change in the sensor’s output can be readily detected as it affects the current in the entire loop.

Alternatives such as connecting in parallel or using a loopback method would not provide accurate measurements, as they would either create an unintended pathway for current that could alter readings or fail to create a complete circuit necessary for the 4-20 mA signal to function properly. Similarly, directly connecting to power does not facilitate the proper functioning of the sensor’s output signal in the context of testing its performance.