In many electrical and electronic applications, electric current sensors are indispensable. Whether for use in a feedback network, in a subcircuit to monitor the operation condition of a system, or as a component in a measurement system such as an energy meter, you're going to want to make sure you use electrical current sensors that are accurate, inexpensive and fast responding.

The three general types of available electrical current sensors include current transformers, Hall effect devices and resistors. For isolation from the voltages of the measured circuit and for the highest accuracy possible, go with the Hall effect current sensor. Resistors are, of course, the least expensive option. When looking for current sensors, consider the following:

1. Buy a Hall effect electric current sensor.

2. Shop for transformer-type current sensors.

3. Obtain resistor-type current sensors.

Action Steps
The best contacts and resources to help you get it done

Make the most accurate current measurements possible with Hall effect electric current sensors

Hall effect current sensors are great for a lot of reasons. They are small and can detect both DC and AC currents; are generally less expensive than current transformers; provide voltage isolation from the circuit being tested, often protecting the test equipment; are highly accurate; and provide a quick response. They're also available in PCB designs.

I recommend: Ampsolution distributes Hall effect current sensors from dozens of different sources, so they have a pretty rich selection. CR Magnetics carries the CR5200 series Hall effect current sensors for DC current sensing up to 20 mA.

For sensing extremely high current, use current transformers as your electric current sensors

Current transformers are not as accurate as Hall effect and resistors because their accuracy depends on burden, rating factor, load, temperature and so on, but they are useful in high-current applications where a bus bar or other large conductor is passed through the eye of the transformer.

I recommend: MeasureAmps carries a line of current transformers covering AC and DC measurements up to 3,000 Amps. Flex-Core also carries a selection, covering currents of up to 6,000 amps.

For lower-budget applications, use a resistor-type electric current sensor

Resistors are typically the lowest cost way to go for an electrical current senser. Current shunts are more specialized, withstanding high currents and offering superior accuracy.

I recommend: Digi-Key carries a line of resistors, specially designed as current sensing resistors, with power dissipation ratings from 1/8 watts up to 100 watts. For surface mount applications, Isotek carries a long list of resistor-type current sensing devices. RC Electronics carries large current shunt resistors that you can use for up to 100 Amp measurements.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  When using a current transformer type electric current sensor, make sure that the conductor passing through the eye of the transformer is not off-center, but passes through the center; otherwise, error will be introduced into the measurement.