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In order that our testers can be used safely and correctly, these criteria are classified according to IEC standards, and depend on the location of the equipment to be measured.

Overvoltage Category I (Cat I): Secondary electrical circuits within a device and running from a wall socket via power supply transformer.

Overvoltage Category II (Cat II): Primary electrical circuits of a device, having a power cord attached and connected to a wall socket.

Overvoltage Category III (CAT III): Primary electrical circuits of a device taking its power directly from a distribution panel, and electrical circuits from a branching point to a distribution outlet.

Overvoltage Category IV (CAT IV): All electrical circuits from the service line to the distribution panel.

What are the tester overvoltage categories?

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