• Megger

Megger® BM11, BM11D Series

5kV Analog/Digital Insulation Testers



  • Choice of test voltages
  • Direct reading display
  • Unique rugged case
  • Guard terminal
  • Large direct reading analog scale
  • Guard terminal
  • Rugged case design
  • 123 mm scale length


  • Choice of test voltagesLarge analog/digital display
  • Built-in timer
  • Locking test leads for safety
  • Battery indicator
  • Weatherproof to IP54
  • Voltage measurement and warning BM11D
  • Large, custom analog/Digital LCD
  • Automatic discharge of capacitance
  • Voltage measurement and warning
  • Tests to 500 GΩ


The Megger® BM11 series of 5 kV Insulation Testers provides a choice of features to suit all applications and budgets.

The traditional BM11 instrument became the industry standard 5 kV tester. It is battery-powered, housed in a rugged case and has a large, simple white-on-black scale. The series has been extended with three analog/digital instruments; the BM11D, BM21 and BM25. These instruments show results and test options on a large, clear analog/digital scale for both practicality and precision. A built-in timer makes both spot tests and PI testing easier to carry out.

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The BM11 series is designed for testing the insulation of high voltage electrical equipment and the wide voltage range also allows it to be applied to low voltage equipment.

Generators, motors, transformers, cables and switchgear all require effective maintenance and the test techniques on the Megger range give valuable diagnostic information. ‘Spot’ Insulation tests that are the most widely used, check on the general condition of electrical insulation, called up in most standards covering equipment design, testing, installation and maintenance.

Insulation suffers from gradual steady decline, as well as occasional sudden damage; the effects of dirt, grease, moisture, vibration and chemical attack can be tracked through the recording of Polarisation Index tests which remove the temperature dependence of raw Insulation Resistance measurements.

For finding more localised insulation problems, the BM25 includes both Step Voltage and Dielectric Discharge tests. Step Voltage identifies local weak spots because they respond differently as the electrical stress is increased, while the Dielectric Discharge test can show up a single bad layer in multilayer insulation.

The key to Predictive Maintenance is the trending of diagnostic tests and this is facilitated on the BM25 by the ability to use a PC to store results over time for trend analysis.

  • Literature
  • Specifications
Insulation Ranges BM11 BM11D
Test Voltages: 500, 1000, 2500, 5000 V
Insulation Resistance Range: 100 kΩ to 100 GΩ; at all test voltages Digital10 kΩ – 50 GΩ @ 500 V10 kΩ – 100 GΩ @ 1000 V 10 kΩ – 250 GΩ @ 2500 V 10 kΩ – 500 GΩ @ 5 kVanalog 100 kΩ to 1 TΩ @ all voltages
Accuracy ±1,5% of arc length ±5% of reading 10 MΩ to 100 GΩ @ 5 kV
Short Circuit Current 1 mA nominal, 2 mA max. 1,8 mA nominal, 2 mA max.
Voltage Range 50 to 1000 V d.c. or a.c. 50 to 1000 V d.c. or a.c.
Accuracy: ±5% ±10 V ±2% ±1 V
Display : Analog Analog / Digital
Operating Temperature : -15 to +55°C(5 to +131°F) -20°C to +50°C(-4 to 122°F)
Storage Temperature -40 to +65 °C(-40 to +149°F) -25°C to +65°C(-13 to 149°F)
Temperature Coeffecient: < 0,04% of arc length per °C (0.2%/°F) 0,2% per °C (0.1%/°F) for test currents >100 nA (Applies over range 0 to 30°C) 0,2% per °C for test currents >100 nA (0.1%/°F) 0,1% per °C for test voltage (0.05%/°F)
Humidity Range 90% RH @ 40°C max. (104°F) 90% RH @ 40°C max. (104°F)
Safety Safety IEC348 IEC1010-1 (1995), EN61010 (1995) to installation category III, 300 V, phase to earth, 500 V phase to phase