Digital Clamp Meter UNI-T UT221, 2000 A AC/DC, True RMS

UNI-T UT221 Digital Clamp Meter, 2000 A AC/DC, True RMS

The UNI-T UT221 is a digital clamp meter designed for measuring AC and DC currents up to 2000 A, as well as voltage, resistance and frequency. It features True RMS measurement, a 63 mm jaw opening, inrush current measurement and a low-pass filter (LPF). The instrument is suitable for electrical equipment diagnostics, maintenance and high-current measurements.

Key specifications: AC/DC current up to 2000 A • True RMS • AC voltage up to 750 V, DC up to 1000 V • 63 mm jaws • CAT III 1000 V / CAT IV 600 V

Key Features

• AC/DC current measurement up to 2000 A. Measures alternating and direct current using clamp jaws without disconnecting the conductor from the circuit.
• True RMS measurement. Measures the true root mean square value of AC voltage and current, including non-sinusoidal waveforms within the instrument's specified measurement limits.
• Inrush current measurement. Captures the starting current of motors and other electrical equipment over a 100 ms measurement interval.
• Low-pass filter (LPF). Helps reduce high-frequency interference during AC voltage and current measurements, particularly in variable-frequency drive applications.
• Large 63 mm jaw opening. Accommodates conductors up to 60 mm in diameter, making the meter suitable for measurements on large electrical cables.
• Current signal output (I-OUT). Converts measured current into a voltage signal at a ratio of 1 mV/A, allowing the current waveform to be observed using an oscilloscope.
• Automatic ranging. Automatically selects the appropriate measurement range for convenient operation.
• Additional measurement functions. Includes MAX/MIN, relative measurement (REL), DC current zero adjustment (ZERO), data hold (HOLD), diode testing and audible continuity testing.
• Backlit LCD display. The main and secondary display areas provide measurement information, while a 66-segment analogue bar graph helps visualise changes in the measured signal.

Applications

The UNI-T UT221 is intended for electricians, electrical maintenance personnel and technicians performing high-current measurements.

Typical applications include inspecting electrical distribution equipment, testing electric motors, maintaining industrial electrical systems and checking DC circuits. The inrush current function is useful for evaluating motor starting current, while the LPF mode is intended for measurements in systems controlled by variable-frequency drives.

Compatibility and Limitations

• Current is measured by clamping around a single conductor. Voltage, resistance and frequency are measured using test leads.
• The I-OUT terminal can be connected to an oscilloscope using the dedicated output cable to observe the current waveform.
• AC current measurement accuracy is specified over a frequency range of 50–60 Hz.
• The frequency measurement input must not exceed 30 V RMS.
• Unlike the UT222, the UT221 does not provide capacitance measurement, temperature measurement or a combined AC+DC measurement function.
• The instrument is not intended for prolonged continuous measurements at very high current levels.

Technical Specifications

Parameter	Specification
Model	UNI-T UT221
Instrument type	Digital AC/DC clamp meter
Sensor type	Hall effect
AC current ranges	660.0 A / 2000 A
DC current ranges	660.0 A / 2000 A
Current resolution	0.1 A / 1 A
Current accuracy, 660 A range	±(2.5% + 20 digits), according to the 2018 operating manual
Current accuracy, 2000 A range	±(2.5% + 5 digits)
AC current frequency response	50–60 Hz
AC voltage ranges	6.600 V / 66.00 V / 660.0 V / 750 V
AC voltage resolution	0.001 V / 0.01 V / 0.1 V / 1 V
Basic AC voltage accuracy	±(1.2% + 5 digits); accuracy may vary by range
AC voltage frequency response	40–400 Hz
DC voltage ranges	6.600 V / 66.00 V / 660.0 V / 1000 V
DC voltage resolution	0.001 V / 0.01 V / 0.1 V / 1 V
Basic DC voltage accuracy	±(0.8% + 1 digit); accuracy may vary by range
Voltage input impedance	≥10 MΩ
Resistance ranges	660.0 Ω / 6.600 kΩ / 66.00 kΩ / 660.0 kΩ / 6.600 MΩ / 66.00 MΩ
Resistance resolution	0.1 Ω / 0.001 kΩ / 0.01 kΩ / 0.1 kΩ / 0.001 MΩ / 0.01 MΩ
Resistance accuracy	Range-dependent, from ±(1.0% + 2) to ±(1.5% + 2)
Frequency ranges	66.00 Hz / 660.0 Hz / 6.600 kHz / 66.00 kHz / 660.0 kHz / 6.600 MHz / 20.00 MHz
Frequency resolution	0.01 Hz / 0.1 Hz / 0.001 kHz / 0.01 kHz / 0.1 kHz / 0.001 MHz / 0.01 MHz
Frequency accuracy	±(0.1% + 3 digits)
Duty cycle measurement	Yes
Continuity test	Audible indication below 30 Ω
Diode test	Yes
Inrush current measurement	INRUSH, 100 ms interval
Low-pass filter	LPF
Current signal output	I-OUT, 1 mV/A
Relative measurement	REL
DC current zero adjustment	ZERO
Additional functions	HOLD, MAX/MIN, automatic ranging
Display	Backlit LCD, 6000 counts
Analogue bar graph	66 segments
Sampling rate	Approximately 3 readings/s
Maximum jaw opening	63 mm
Maximum conductor diameter	60 mm
Automatic power-off	Approximately 15 min
Power supply	9 V (6F22)
Safety rating	CAT III 1000 V / CAT IV 600 V
Safety standards	IEC/EN 61010-1, IEC/EN 61010-2-032, IEC/EN 61010-2-033
Insulation	Double insulation
Pollution degree	2
Operating temperature	0–50 °C, subject to relative humidity limits
Storage temperature	−20 to +60 °C
Maximum operating altitude	2000 m above sea level
Dimensions	298 × 107 × 47 mm
Weight	Approximately 726 g

Accuracy notation: ±(% of reading + number of least significant digits). The stated basic accuracy does not automatically apply to every measurement range. Manufacturer-specified accuracy conditions: 23 ± 5 °C and relative humidity up to 80%.

Design and Controls

The instrument features a rotary function selector and dedicated control buttons. The LCD provides main and secondary readings, allowing parameters such as AC current and frequency to be displayed simultaneously.

A selector in the terminal area allows the operator to choose between the measurement input and the current signal output. The clamp jaw assembly includes a finger guard for safer handling.

Important Operating and Safety Notes

• Do not exceed the measurement limits of 2000 A AC/DC, 750 V AC or 1000 V DC.
• Before measuring DC current, perform the ZERO adjustment. Position the conductor in the centre of the jaws, as incorrect positioning may introduce additional measurement error.
• Avoid prolonged high-current measurements because excessive heating of the magnetic circuit may affect accuracy.
• Disconnect circuit power and discharge all capacitors before measuring resistance or performing diode and continuity tests.
• Do not exceed 30 V RMS at the frequency measurement input. Do not apply more than 5 V to the I-OUT terminal.
• Do not use the instrument if the housing or test lead insulation is damaged.

Package Contents

• UNI-T UT221 digital clamp meter.
• One pair of test leads.
• Current signal output cable.
• Wrist strap.
• Tool case.