• The range can be increased by using Current Transformer instrument.
• A current transformer is a type of transformer that is designed to provide an isolated current output that is proportional to the current flowing through its primary winding.
• By passing the current to be measured through the primary winding of the CT, a much larger current can be obtained at the secondary winding, which can be used to drive the instrument.
• By using a CT in series with the instrument, the range of the instrument can be extended to measure much larger currents than it would be able to measure directly.

For example, if an instrument has a maximum range of 5A, a CT with a turns ratio of 100:1 can be used to measure currents up to 500A. The instrument is connected in series with the secondary winding of the CT and is only exposed to a small fraction of the actual current being measured.

Therefore, using a CT in series with the instrument is an effective way to extend the range of an instrument without requiring a larger, more expensive instrument to be used for high current measurements.