A donut transformer is commonly used when AC current levels to be monitored exceed 75 amperes. Current transformer rated 100:5 will provide a secondary current of 5 AC amperes when a single primary turn is passed through the donut with a 100 ampere load. The donut transformer provides additional isolation from the conductor. The secondary leads are 2 feet long and may be extended up to 10 feet using at least 12 gauge copper wire. If the distance is greater than ten feet, please consult the factory. A 50:5 amp donut is the lowest rating that Simpson normally carries. A donut can be used for ratings below 50 amps by wrapping either the primary wire passing through the core, or by wrapping the secondary wires leading to the meter. This is shown on the next page. Other ratings are available on special order. Call the factory with your specifications.