The UT3550 measures battery internal resistance and voltage together using a 4-wire Kelvin connection and 1 kHz AC injection — the method that reveals a weak cell before it fails under load. It resolves internal resistance from 0.001 mΩ to 30 Ω at ±0.5% and voltage to 100 V at ±0.05%, covering everything from small consumer cells to large industrial battery banks.
A 4-wire connection removes lead resistance for accuracy at low ohms, a comparison function sorts pass/fail against set limits, and results log to 500 groups with CSV export over USB-C. The IP65 body and rechargeable pack suit field and maintenance work. It's backed by UNI-T's nearly 40 years of test-meter manufacturing.
Key Features
AC-injection internal-resistance method (1 kHz)
Internal resistance 0.001 mΩ to 30 Ω, ±0.5%
Voltage 0.0001 V to 100 V, ±0.05%
4-wire Kelvin connection removes lead resistance
Comparison function with pass/fail sorting
Data logging to 500 groups; CSV export over USB-C
Dual display (LCD & OLED); IP65 sealing
Rechargeable 7.4 V 2000 mAh Li-ion
UT3550 Details
Internal Resistance & Voltage Together
Internal resistance rises as a cell ages, often well before its open-circuit voltage drops. By measuring resistance (0.001 mΩ–30 Ω) and voltage (to 100 V) at the same time, the UT3550 flags a weakening cell while it still reads a normal voltage.
4-Wire Kelvin Accuracy
A 4-wire Kelvin connection separates the current and sense paths so lead and contact resistance don't corrupt the reading — essential for the milliohm-level measurements that distinguish a healthy cell from a tiring one.
Sorting & Logging
A comparison function sorts cells pass/fail against set limits for fast battery-bank screening, and logging to 500 groups with CSV export over USB-C builds the record a maintenance program needs.
Field Build
A dual LCD/OLED display, IP65 sealing, and a rechargeable Li-ion pack make the UT3550 practical for moving down a rack of cells in the field.
Applications
UPS, telecom, and stationary battery-bank maintenance; testing consumer and industrial cells from small to large; incoming inspection and pass/fail sorting; and preventive programs that track internal resistance over time.
Frequently Asked Questions
Why measure internal resistance instead of just voltage?
Internal resistance rises as a battery ages, often before voltage drops — so it catches a weak cell earlier.
What is the 4-wire Kelvin method?
It uses separate current and sense leads so lead and contact resistance don't affect the milliohm-level reading.
Can I export results?
Yes — log to 500 groups and export CSV over USB-C.
⚠️ WARNING (California Proposition 65): This product may contain chemicals known to the State of California to cause cancer, birth defects, or other reproductive harm. For more information, please visit www.P65Warnings.ca.gov.
