HT Instruments HT4011 AC Clamp Meter. Clamp-on meter HT4011 can measure AC current up to 400A, AC/DC voltage, resistance, continuity test, capacitance, temperature with type K probe, frequency, duty cycle and diode test. The instrument complies with IEC/EN61010-1 under CAT III 600V and is suitable for measurements both in civil and industrial sites.