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BT51 Low Resistance Ohmmeter

Megger BT51 Low Resistance Ohmmeter makes measurements by passing a current through the conductor under test & also monitoring the voltage across it.

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Megger BT51 Low Resistance Ohmmeter

The Megger BT51 Milliohmeter makes measurements by passing a current through the conductor under test and also monitoring the voltage across it. 

The test current is limited by a simple current limiting circuit and is measured by monitoring the voltage across a resistor.  The test current is maintained at a nominal 2 A, and as the measurement is ratiometric, the reading is unaffected by any current variations.

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

The ohmmeter is protected up to 240 V a.c. by a relay circuit that keeps the instrument in a safe mode isolated from the mains supply.  Again, this safeguard is effective whether or not the instrument has been switched on. Operation of the instrument is simple, there being only one range switch to set. Power is supplied by internal rechargeable cells and the charger unit is incorporated into the case.


Megger BT51 Key Features:

  • Protected against inadvertent connection to the mains supply
  • High test current - 2 A DC (e.g., for aircraft bond testing)
  • Four terminal measurement
  • Two measuring ranges (2000 mΩ and 20,00 mΩ) and maximum resolution of 0,01 mΩ
  • 3 1/2 digit LED display, which is helpful in a poorly lit environment
  • Protection against 240V a.c. and warning lights for added safety
  • Robust, shockproof, weatherproof, portable case which has has a hinged, detachable lid
  • Can used very long test leads
  • New duplex connect test leads - Now supplied as standard


Megger BT51 Applications:

  • Commissioning and maintenance of substation equipment where measurements can be made on such things as:
    • busbar joints
    • switch and circuit breaker contact resistance
    • fuse resistance
    • cold lap welded joints in aluminium earthing strip and earth bonding
  • Maintenance of overhead transmission lines, where “hot” joints can be tested before and after their remaking or re-compression
  • Bond  testing  aircraft  frames, incl. the bonding of electronic dischargers and fuel tanks
  • Testing earth bonds in mines
  • Rail bond testing, where a rail is used as part of a communication system or for power transmission
  • Testing the integrity of lightening conductors


What come with the Megger BT51?

  • Megger BT51 Low Resistance Ohmmeter
  • Supply Lead for Battery Charger
  • Duplex Handspikes with 2.5m (8ft) Test Leads
  • Operating Instruction Book
  • DH1-C  Two wire, four terminal duplex twist probe lead set - 3m


 The various models of the Megger BT51:

  • (1006-605) BT51 milliohmeter (240V) with DH1-C
  • (1006-606) BT51 DLRO 120V with DH1-C

The only major difference between the products is 1006-606 uses 120V operation rather than 240V




Comparison Chart for: Megger BT51 Low Resistance Ohmmeter

Nominal currentUp to 10 AUp to 10 AUp to 10 AUp to 10 AUp to 2 A
No of ranges with power limited to 0.25 W6666
No of higher power ranges22
DisplayLCD BacklitLCD BacklitLCD Backlit
Results storage and download
Power supply
Rechargeable battery
Weight6.7 kg6.7 kg2.6 kg2.6 kg4.5 kg