• Four-wire Kelvin measurement, 0.05 percent basic accuracy (0.15 percent on the 5 mohm range)
• Measures 1 micro-ohm to 2500 ohms across seven ranges, resolution down to 0.1 micro-ohm
• Selectable test currents: 1 mA, 10 mA, 100 mA, 1 A, and 10 A
• Three test modes: resistive (instantaneous), inductive (continuous), auto (repetitive)
• Up to 60 minutes continuous testing at 10 A; measurement stabilization in under 2 seconds
• Temperature compensation with selectable metal type (copper, aluminum, or custom) via optional RTD probe
• Two programmable alarms with high or low triggering
• Stores up to 1500 test results; automatic discharge of residual charge on the sample
• Built-in rechargeable NiMH pack, about 5000 tests at 10 A per charge
• Sealed case IP64 (cover closed), IP53 (cover open); included DataView software

• Bonding and joint resistance: mechanical bond tests, aircraft and rail bonds, metallic coating resistance
• Contact resistance on circuit breakers, switches, and busbar and cable connections
• Acceptance and maintenance testing of transformer and motor windings
• Ground bond and continuity verification
• High-precision component, cable, and quality-control resistance checks

• Type: laboratory-grade portable micro-ohmmeter, four-wire Kelvin method (de-energized circuits only)
• Resistance range: 1 micro-ohm to 2500 ohms, seven ranges (5 mohm, 25 mohm, 250 mohm, 2500 mohm, 25 ohm, 250 ohm, 2500 ohm)
• Resolution: 0.1 micro-ohm (best), stepping to 100 mohms on the top range
• Accuracy (1 year, 23 C plus or minus 5 C): plus or minus (0.05 percent + 3 micro-ohms) typical; plus or minus (0.15 percent + 1.0 micro-ohm) on the 5 mohm range
• Test current per range: 10 A (5, 25, 250 mohm), 1 A (2500 mohm), 100 mA (25 ohm), 10 mA (250 ohm), 1 mA (2500 ohm)
• Voltage drop by range: 50 mV to 2500 mV; open circuit voltage 7 VDC max
• Test modes: resistive, inductive, auto
• Temperature measurement: 3-wire 100 ohm platinum RTD, accuracy plus or minus 0.5 C, resolution 0.1 C (RTD probe optional, Cat. #2129.95 or #2129.96)
• Alarms: two programmable, high or low trigger, 0.0 to 2500.0 ohms
• Memory: 1500 test results, with DataView software (included)
• Power: rechargeable NiMH 6 V, 8.5 Ah pack; charger 120/240 VAC plus or minus 20 percent (45 to 400 Hz)
• Battery life: about 5000 tests at 10 A (typical); auto power off below 5.0 V
• Overload input protection: 250 Vrms; fuses F1 16 A / 250 V (6.3 x 32 mm), F2 2 A / 250 V (5 x 20 mm)
• Dimensions: 10.63 x 9.84 x 7.09 in (270 x 250 x 180 mm); weight 8.1 lbs (about 3.69 kg) without leads
• Case protection: ABS polycarbonate, IP64 cover closed, IP53 cover open
• Operating temperature: 14 to 131 F (-10 to 55 C), 10 to 80 percent RH; altitude below 2000 m
• Safety: EN 61010-1, 50 V CAT III, Pollution Degree 2

The AEMC 6255 is AEMC's most accurate micro-ohmmeter, built for jobs where 0.05 percent matters: acceptance testing on switchgear, transformer and motor windings, and critical bonded joints. The four-wire Kelvin front end cancels test lead resistance, and seven ranges cover 1 micro-ohm to 2500 ohms with resolution down to 0.1 micro-ohm. You select the test current (1 mA, 10 mA, 100 mA, 1 A, or 10 A) and the test mode: resistive (instantaneous), inductive (continuous), or auto (repetitive). The 6255 can run up to 60 minutes continuously at 10 A, with a thermal switch protecting the range and fast stabilization in under two seconds.

Temperature compensation with selectable metal type (copper, aluminum, or custom) corrects readings to a reference temperature using an optional RTD probe, and two programmable high or low alarms flag out-of-spec results. Up to 1500 results store to memory. The sealed, safety-yellow case is rated IP64 with the cover closed, and a built-in NiMH pack delivers about 5000 tests at 10 A per charge.

Included DataView software handles configuration, data download, and reporting for acceptance and maintenance records. The 6255 tests de-energized circuits only.