MPK-257 10 A Digital Micro-ohmmeter (0.1 µΩ)

Note: the MPK-257 is the high-resolution variant (0.1 µΩ) with temperature compensation. For measurements where 1 µΩ resolution is sufficient, choose the MPK256.

MPK257 — the versatile micro-ohmmeter up to 10 A

The MPK257 is a portable, microprocessor-controlled instrument for accurately measuring very low resistances. With 6 selectable test currents from 1 mA to 10 A — each continuously adjustable from 0 to 100% — and a measurement range from 0.1 µΩ to 2,000 Ω, the MPK257 covers a wide range of applications.

The 4-wire (Kelvin) measurement principle eliminates errors caused by test lead and contact resistances. The output voltage is up to 10 V DC (open circuit, at 1 A). Internal offset compensation usually makes reversing the current unnecessary. If there is a temperature difference between the measuring points, measure in both current directions and take the average.

Operation is simple: connect the test leads, select the test current and press start. After a few seconds, the reading appears directly on the display with unit indication (Ω, mΩ or µΩ). The rugged IP65 case (6.5 kg) makes the instrument suitable for both laboratory and field work.

Applications

• Switches and circuit breakers — contact resistance measurement on switch contacts, disconnectors and relays
• Transformers — DC resistance measurement of windings to find poor connections and deviations between phases
• Motors and generators — resistance measurement of rotor and stator windings, phase symmetry
• Busbar connections — verification of bolted and welded joints for transition resistance
• Cables and conductors — resistance measurement of cable samples, cable lugs and connectors
• Grounding systems — measurement of earth connections and bonding
• Quality control — incoming inspection of components and semi-finished products

Key features

• 6 test currents — 1 mA, 10 mA, 100 mA, 1 A, 5 A and 10 A, each continuously adjustable (0–100%)
• Resolution 0.1 µΩ — at 10 A test current
• Temperature compensation — with the supplied temperature sensor
• Measurement range up to 2,000 Ω — at 1 mA test current
• Accuracy ± 0.10% — of reading + 3 digits
• 4-wire (Kelvin) measurement — elimination of test lead and contact resistances
• Output voltage up to 10 V — open circuit voltage at 1 A
• Built-in thermal printer — direct printout of measurement results
• 30,000 readings memory — transferable via USB
• IP65 enclosure — dust and waterproof with closed lid, 6.5 kg
• Rechargeable LFP battery — 12 V, 6,000 mAh, or mains supply 220–240 V~
• Offset compensation — internal offset is corrected automatically
• USB and Android app — data transfer via USB, remote control via an Android app
• 2-year warranty — standard Megabras factory warranty

MegaLogg 3 software

The MPK257 is supplied with MegaLogg 3 desktop software for transferring, analysing and reporting measurement data via USB. You can also control the instrument remotely via an Android app.

When to choose the MPK257, MPK105R or MPK215R?

The MPK257 is the versatile model: 6 test currents up to 10 A, with a resolution of 0.1 µΩ, a wide measurement range up to 2,000 Ω, ideal for general resistance measurements on switches, windings and cables. For higher test currents up to 100 A with BSG mode for substations, the MPK105R is the choice. For maximum test current up to 200 A in heavy industrial applications, see the MPK215R.

Key features

• Alphanumeric display
• Resolution: 0.1 µΩ
• Temperature compensation
• Resistance reading: up to 2,000 Ω
• Up to 10 A test current
• Kelvin-type measurement (4-wire)
• Powered by internal battery
• Direct reading (up to 4½ digits)
• Overheat protection

Test currents
1 mA – 10 mA – 100 mA – 1 A – 5 A – 10 A.

Each current may be continuously adjustable from 0 to 100%.

Resistance ranges
0-200 mΩ @ 10 A.
0-1,000 mΩ @ 5 A.
0-200 mΩ @ 1 A.
0-2,000 mΩ @ 100 mA.
0-20 Ω @ 10 mA.
0-2,000 Ω @ 1 mA.

Accuracy of test current
± 3%.

Resolution
0.1 µΩ @ 10 A.

Output voltage
Up to 10 Vdc (open circuit) @ 1 A.

Measurement Principle
Four-terminal, Kelvin-type.

Basic Accuracy of resistance measurement
± (0.10 % of reading + 3 digits).

Advanced features
Digital direct reading of very low resistances in the alphanumerical display, with up to 4½ digits. Very fast and accurate measurements. Built-in printer.

Built-in memory
For up to 30,000 measured values.

Serial data output
USB.

Environmental
IP65 with closed lid.

Safety class
Meets the requirements of IEC 61010-1.

Power supply
Rechargeable LFP battery 12 V, 6000 mAh or 220 – 240 V~ mains supply.

Battery charger
For 220 – 240 V~ mains supply or auxiliary 12 V supply input.

Operating temperature range
-5 °C to +50 °C.

Storage temperature range
-25 °C to +70 °C.

Humidity range
95% UR (non condensing).

Equipment weight
Approx. 6.5 kg.

Dimension
378 x 308 x 175 mm.

Scope of supply

• 2 combined current and potential leads
• Ground cable
• Power cord
• USB cable
• Auxiliary external power cord 12 V (charging)
• Auxiliary external power cord 12 V (charging or measuring)
• Temperature sensor
• User guide
• MegaLogg 3 software
• Carrying bag for the accessories