How to Use an AC Current Sensor Application Note

Using Acromag’s AC Current Sensor Model 5020-350


Transmitters with DC current input can be used used in conjunction with an external AC Current Sensor to precondition an AC current input signal. This sensor is a highly accurate toroidal instrument transformer that converts an AC current signal to a safe, low-level, DC milliampere signal (0 to 11.17mA).

The transmitters only accept the isolated low-level signal produced by the AC current sensing transformer and cannot be connected directly to the source of AC power without damage or safety risk. The AC Current Sensor is fully insulated and designed for mounting near the source of the AC current. The input AC current range is a simple function of the number of turns placed on the AC Current Sensor. The benefits to using an external sensor (external from the transmitter) include the following:

Low Losses:

It is not practical to run AC currents over long distances because of significant resistance voltage drops at high currents. The low-level DC milliampere signal output from the AC Current Sensor can be transmitted safely over long distances, allowing the transmitter to be remotely located from the AC power wiring.


The AC Current Sensor’s output leads can be open or short-circuited and these conditions do not affect the AC current loop or cause damage to the sensor. Likewise, the wires connecting the AC Current Sensor to the transmitter can be easily removed from the transmitter’s input terminals without concern or hazard.

Ease of Calibration:

The AC current input range can be easily scaled in the field by simply changing the number of primary turns at the sensor, with no additional calibration required. That is, the AC current input span is a simple function of the number of primary turns placed on the AC Current sensor and sensor/transmitter calibration is not affected by this.

Supported Products


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