The EG30xx and EG4xxx are Listed Devices, certified to be used with CTs that have the following specifications: UR and CSA, 0.333Vrms output at rated current, and 600V insulation. While any CT with these specifications can be safely attached, only CTs listed in section B.6 of the EG30xx Owner's Manual and section B.6 of the EG4xxx Owner's Manual have been evaluated by eGauge Systems to ensure correct performance and accuracy.

As a general rule, any CT used with an older model of eGauge should be automatically supported by a newer model. For example, the CTs used with an eGauge2 should be supported by an EG30xx or EG4xxx. Moving from a newer model of eGauge to an older model may require a firmware update to add support for certain CTs. This assumes that the CTs were originally purchased through eGauge Systems, and not a third party.

Connecting any other hardware to a CT port can damage the eGauge and will void the warranty.