AC Leakage Current Clamp Meter UNI-T UT251C+ , 60 A, 1 µA, Bluetooth

UNI-T UT251C+ AC Leakage Current Clamp Meter, 60 A, 1 µA, Bluetooth

The UNI-T UT251C+ is a digital clamp meter designed for measuring low AC leakage currents and currents up to 60 A without disconnecting the circuit. It provides current and frequency measurement together with harmonic analysis up to the 20th order. Built-in Bluetooth connectivity enables measurement monitoring and data recording through a mobile application.

Key specifications: AC up to 60 A • 1 µA resolution • 40 mm jaw • 20 harmonics • Bluetooth • CAT III 600 V

Key Features

• High measurement sensitivity – the lowest 3.000 mA measurement range provides 1 µA resolution for monitoring small leakage currents.
• Non-intrusive current measurement – measures current without disconnecting conductors or interrupting the electrical circuit.
• 40 mm jaw opening – accommodates larger conductors or multiple circuit conductors for residual current measurements.
• Harmonic analysis – measures harmonics up to the 20th order, including harmonic amplitude, relative values, THDF and THDR.
• Low-pass filter (LPF) – reduces the influence of higher-frequency components when evaluating the fundamental-frequency current.
• Automatic ranging – automatically selects the appropriate measurement range.
• Bluetooth connectivity – works with the UNI-T Smart Measure application for measurement monitoring, data logging, graphs and reports.
• MAX/MIN and HOLD functions – capture maximum and minimum readings and freeze the displayed measurement.
• Dual LCD display – simultaneously displays measured current and frequency. The backlight and integrated flashlight improve visibility in poorly illuminated areas.

Applications

The UNI-T UT251C+ is intended for electricians, electrical maintenance personnel and technicians performing:

• Leakage current measurements in electrical installations and protective earth conductors.
• Leakage current testing of electric motors, household appliances and other electrical equipment.
• Current measurements in distribution boards and control circuits.
• Frequency measurements and harmonic analysis in low- and medium-current circuits.

Residual current can be measured by clamping all relevant live circuit conductors together or by measuring the protective earth conductor separately. Clamping a single live conductor measures the AC current flowing through that conductor.

Compatibility and Limitations

• Designed for AC current measurement only; DC current measurement is not supported.
• Maximum rated measurable current: 60 A RMS.
• Conservatively specified AC current measurement bandwidth: 45 Hz–1.2 kHz.
• The user manual specifies frequency measurement accuracy from 40 Hz to 5 kHz with an input current amplitude of 600 µA–60 A.
• Specified harmonic measurement accuracy requires a fundamental current of at least 1 mA and a fundamental frequency of 40–60 Hz.
• Bluetooth communication is supported through the UNI-T Smart Measure application. The manual specifies Android 5.0 or later and iOS 10.0 or later. Requirements for newer application versions may differ.
• Designed for indoor use within CAT III 600 V measurement category limits.

Technical Specifications

Parameter	Specification
Manufacturer	UNI-T
Model	UT251C+
Product type	AC leakage current clamp meter
Measured quantities	AC current, frequency, harmonics
Maximum measurable current	60 A RMS
AC current measurement bandwidth	45 Hz–1.2 kHz (conservative limit)
Frequency measurement	Up to 5 kHz
Harmonic measurement	1st–20th order
Harmonic resolution	0.1%
Harmonic parameters	THDF, THDR, amplitude
Jaw opening	40 mm
Display	Dual HTN LCD, 3000 counts
Sampling rate	2 readings/s
Range selection	Automatic
Additional functions	LPF, MAX/MIN, HOLD
Wireless connectivity	Bluetooth
Mobile application	UNI-T Smart Measure
Automatic power-off	Approximately 15 min
Power supply	3 × 1.5 V AAA batteries
Measurement category	CAT III 600 V
Insulation	Double insulation
Safety standards	IEC/EN 61010-1, IEC/EN 61010-2-032
Electromagnetic compatibility	EN 61326-1, EN 61326-2-2
Pollution degree	2
Operating temperature	0–40 °C
Storage temperature	–10–60 °C
Relative humidity	Up to 75% (0–30 °C); up to 50% (30–40 °C)
Maximum operating altitude	2000 m
Dimensions	200.1 × 70.5 × 40 mm
Weight	Approximately 350 g

AC Current Measurement Ranges and Accuracy

Range	Resolution	Accuracy, 40–60 Hz	Accuracy, above 60 Hz to 1.2 kHz
3.000 mA	0.001 mA	±(2% + 5)	±(3% + 9)
30.00 mA	0.01 mA	±(1% + 5)	±(2% + 9)
300.0 mA	0.1 mA	±(1% + 5)	±(2% + 9)
3.000 A	0.001 A	±(1% + 5)	±(2% + 9)
30.00 A	0.01 A	±(1% + 5)	±(2% + 9)
60.0 A	0.1 A	±(1% + 5)	±(2% + 9)

The specified accuracy applies to 5–100% of the selected range under the conditions defined in the user manual. Manufacturer documents differ on the lower frequency limit; for measurements between 40 and 45 Hz, the applicable accuracy should be confirmed using the documentation supplied with the particular instrument. Accuracy is expressed as a percentage of the reading plus a number of least significant digits.

Frequency Measurement

Range	Resolution
99.99 Hz	0.01 Hz
999.9 Hz	0.1 Hz
5.000 kHz	0.001 kHz

Frequency measurement accuracy: ±(0.1% + 5), within 40 Hz–5 kHz and at a measured current amplitude of 600 µA–60 A.

Harmonic Measurement Accuracy

Harmonic order	Resolution	Accuracy
1–6	0.1%	±(3.5% + 10)
7–8	0.1%	±(4.5% + 10)
9–10	0.1%	±(5% + 10)
11–15	0.1%	±(7% + 10)
16–20	0.1%	±(10% + 10)

Specified harmonic accuracy applies with a fundamental frequency of 40–60 Hz, a fundamental current of at least 1 mA and harmonic frequencies not exceeding 1.2 kHz.

Construction and Operation

The meter features 40 mm clamp jaws, a protective finger barrier and a conductor centering mark. Dedicated buttons provide access to HOLD, MAX/MIN, LPF, HARM and Bluetooth functions.

The dual LCD displays the primary measurement and additional information. A backlit display and integrated flashlight facilitate operation in low-light environments.

Important Operating and Safety Notes

• Do not exceed 60 A RMS or the CAT III 600 V measurement category limits.
• Keep the measured conductor centered in the jaws and ensure that the jaws are fully closed. An off-center conductor can introduce an additional error of up to ±1% of the reading.
• Specified current measurement accuracy is defined at an ambient temperature of 18–28 °C; an additional temperature-related error applies outside this range.
• The clamp jaws contain a precision sensor. Avoid impact and abrupt jaw closure.
• Do not operate the meter if it is damaged or wet. Keep your hand behind the protective barrier when measuring hazardous live conductors.
• The 1 µA resolution does not represent the minimum current for which measurement accuracy is guaranteed.

Package Contents

• UNI-T UT251C+ clamp meter – 1 pc.
• 1.5 V AAA batteries – 3 pcs.
• Carrying bag – 1 pc.