• 2A nominal test current with limiting circuit
  • ±1% ±2 digits accuracy (32 to 122°F)
  • Two measuring ranges:
    • 2000mΩ with 1mΩ resolution
    • 20.00mΩ with 0.01mΩ resolution
  • Relay protection circuit (effective up to 240VAC)
    • Effective whether instrument is on or off
    • Protection from inadvertent supply connection
  • Weatherproof and shockproof portable case
  • Hinged detachable lid
  • Can be used with very long test leads
  • Meets safety requirements for IEC 610101-1
  • EMC in accordance with IEC61326-1

What's in the Box

  • 4 Ah NiCd rechargeable battery
  • Supply lead for charging battery
  • Duplex handspikes with 8ft test leads
  • Operating instruction book
  • DH1-C 2-wire, 4-terminal duplex twist probe lead set


The Megger BT51 Milliohmmeter takes measurements by passing a current through two terminals on the conductor as well as monitoring the voltage across it. This measurement is ratiometric, meaning it is unaffected by current variations. The BT51 uses the four-terminal method of measurement. The main advantage of this method is that the resistance of the test leads is not included in the measurement, which is important when the resistance is very low.

This meter has a 3 1/2 digit LED display to facilitate use in low light levels. Two LEDs on the front panel indicate battery condition and whether test current is flowing when a measurement is being made. A red warning light indicates the presence of a dangerous voltage if the test leads are accidentally placed across a live circuit. This warning takes place whether or not the instrument has been switched on.

Megger BT51 Milliohmmeter Applications

  • Measure the resistance of metalwork bonding on large frames, structures, & aircraft
  • Earth bond testing
  • Able bond testing
  • Measure the resistance of lightning conductors
  • Check bus bar continuity
  • Check the resistance between metal points on the aircraft structure