ACheck to see if jumper J3, located on the rear of the ammeter, is correctly installed for ‘-DC1’ models (i.e., it shorts out the two small pins). ‘-DC1’ models are shipped with J3 installed, which configures the ammeter to operate from +5 to 40Vdc power supplies. When J3 is removed, the ammeter will only operate from +36 to +75Vdc power supplies.