The 1201 is designed to measure one 4–20mA transmitter, with either external or internal current loop excitation. The Module provides a single current input channel and a power output channel providing the option to connect the internal excitation into the current loop circuit. If the excitation channel is used, power is switched off after the measurement to conserve energy. A programmable warm-up time enables the excitation to be applied in advance of measurement, to allow for settling time in the external circuit. Different 4–20mA transmitters require different times to reach stability after the application of excitation. The 4–20mA transmitter manufacturer may need to be contacted regarding the recommended settling time, since this specification may not
be published. If the transmitter requires continuous excitation, then an external excitation power supply may be used, or the internal excitation may be configured for continuous power.