UT139A Digital Multimeter True RMS

The UT139 series true RMS digital multimeter is characterized by high reliability, high safety, automatic ranging, and handheld design. It features a large digital screen with high resolution, full-range overload protection, and a unique appearance. It also has VFD (Variable-frequency Drive) measurement capabilities, enabling stable measurement of variable-frequency voltage or current in environments with high-frequency interference. Combined with true RMS measurement, data hold, relative measurement, maximum/minimum value measurement, undervoltage warning, backlight, and automatic shutdown functions, it becomes a new generation of practical electrical measuring instruments with superior performance. It is an ideal tool for the testing, maintenance, and repair of electrical equipment in various colleges and universities, metallurgical plants, communications, manufacturing, petroleum, power, OEM manufacturing, and electrical circuits.

The UT139A is the basic model in UNI-T's UT139 series of true RMS digital multimeters, positioned in the entry-level professional measurement tool market. This series is designed for electrical engineers, electronics engineers, maintenance technicians, and students in related fields, and is suitable for various applications such as power equipment maintenance, industrial automation testing, and home appliance repair.

Product Description from the Supplier

Xi'an Mingxi Taida Information Technology Co., Ltd. brings over 12 years of industry expertise to deliver cutting-edge measurement and control solutions.With progressed computerization forms and strict quality control, we guarantee each item meets the most noteworthy guidelines for proficient applications.

Description

Features of the UT139A Digital Multimeter True RMS

• True RMS Measurement - Technical Advantages

Ordinary average value multimeters can only accurately measure pure sine waves. True RMS multimeters can accurately measure any waveform, including ( Square waves, sawtooth waves, and other non-sine waves, PWM waveforms output from switching power supplies, Chopper waveforms from LED dimmers, SPWM waveforms output from frequency converters.)

Application- Modern electronic devices extensively utilize non-sinusoidal signals such as switching power supplies and frequency converters. Traditional multimeters introduce 10%-40% error when measuring these signals, while true RMS multimeters ensure measurement accuracy.

True RMS measurement is a method for measuring the effective value of AC voltage or current, regardless of waveform distortion, and can accurately calculate the RMS value—this is crucial when testing modern electronic equipment with non-sinusoidal signals such as thyristors, frequency converters, and switching power supplies.

• VFC frequency conversion measurement function

The VFC (Variable Frequency Converter) measurement function is specifically designed for motor control systems driven by frequency converters. Frequency converters output high-frequency PWM modulated waveforms, which contain numerous high-order harmonics, causing significant interference when measured with ordinary multimeters.

Application- Inverter (VFD) output voltage measurement, servo drive testing, soft starter output detection, AC voltage measurement for any signal containing high-frequency interference.

• NCV non-contact voltage detection function

The UT139 series is a professional-grade true RMS digital multimeter series launched by UNI-T for electrical repair and maintenance, filling the market gap between the entry-level UT33 series and the mid-to-high-end UT61 series.

The UT139 Series Includes Four Main Models

Key upgrades of the UT139 series compared to its predecessors (such as the UT39 series):

• Added VFC frequency conversion measurement function
• Added NCV non-contact voltage detection function
• Increased true RMS measurement bandwidth to 1kHz (UT139B/C)
• Expanded frequency measurement range to 10MHz

DC Voltage Measurement

AC Voltage Measurement

VFC frequency conversion measurement mode

Data Hold- Application

• Measuring locations that are difficult to observe simultaneously
• Preserving readings in low-light environments
• When peak data needs to be recorded

Relative Measurement (REL)- Application

• Measuring line voltage drop (measure no-load first, then load, automatically calculate voltage drop)
• Calibrate measurement errors
• Compare deviations of multiple components

Maximum/Minimum Value Records- Application

• Monitoring peak startup current
• Recording power supply fluctuation range
• Observing load changes

Automatic/manual range switching​​​​​​​

Applications:

✅Professional Electrician: Routine electrical inspection and circuit troubleshooting

✅Electronics Engineer: Circuit board testing and component parameter verification

✅Equipment Maintenance Personnel: Routine maintenance of factory equipment

✅HVAC Installation and Repair: Electrical testing of refrigeration systems

✅Vocational Education: Practical training for electronics/electrical engineering majors in colleges and universities

✅DIY Enthusiasts: Home appliance repair and electronic project development

Key Usage Tips

✅Do not exceed the measurement range: The measured voltage must not exceed 600V DC/AC

✅Select the correct range: Estimate the measured value before measurement and select an appropriate range

✅Current measurement requires series connection: The circuit must be disconnected before connecting the instrument in series

✅Do not switch ranges while the circuit is energized: Disconnect the circuit before changing the range

✅Pay attention to polarity indication: A "-" symbol indicates that the positive and negative terminals are reversed

Custom Design

We get it that standard arrangements do not continuously meet one of a kind prerequisites. Our experienced building group gives comprehensive OEM/ODM customization administrations. Whether you require adjusted recurrence ranges, specialized activating alternatives, or custom frame components, we work closely with you to create the idealize arrangement. Our adaptable plan approach guarantees your particular application needs are completely tended to whereas keeping up our quality standards.

Why Select MXTD

Proven Encounter: Over 12 a long time of specialized skill in estimation and control frameworks development.

Expert Designing: Our gifted R&D group ceaselessly innovates to convey cutting-edge arrangements that keep you ahead of industry demands.

Quality Confirmation: Strict fabricating forms and comprehensive testing conventions guarantee dependable, steady performance.

Comprehensive Back: From starting meeting through progressing support, our committed group gives responsive specialized assistance.

Secure Conveyance: Collaborating with trusted coordinations suppliers guarantees secure, followed, and safety net provider shipment of your equipment.

Customer Center: We prioritize your victory with standard follow-ups, fast issue determination, and personalized benefit approaches.

FAQ:

• Why display "OL"? 

A: Beyond the range, please choose a larger capacity.

• Why unstable readings?

A: Interference signal, please use shielded cable. Poor contact of the probe, please clean the probes and jacks.

• Why current measurement is not working?

A: Fuse blows, please contact repairman to replace fuse.

• Why NCV does not respond?

A: The signal is too weak, please near a power cord or outlet.

• Why does the reading fluctuate when measuring LED power supply?

A: The LED driver outputs a high-frequency PWM waveform. Please use VFC mode for measurement to obtain a stable reading.

• NCV cannot detect the voltage that the test pen can normally measure?

A: NCV can only detect AC voltage and requires a certain electromagnetic field strength to trigger. After confirming it is AC power, test it by approaching the wire or the inside of the socket.

• When measuring high resistance values, the reading rises slowly?

A: When measuring high resistance values, the instrument requires a longer time to charge the capacitor. Please wait for the reading to stabilize before recording.

Contact Us

If you are looking for an affordable excellent choice. As the UT139A Digital Multimeter product line, the UT139A Digital Multimeter True RMS is a basic handheld True RMS digital multimeter market.It doesn't make you pay for features you don't need, yet it fully meets your requirements in terms of key measurement capabilities.

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