About the BLRT

The BLRT (bond, loop and joint resistance tester) from MK Test Systems provides automatic testing of bond circuits to assure electrical continuity between conductive parts. The tool provides computer controlled automatic testing of bond circuits, automatic analysis of measured values and logging of test results.

Why use an Automatic Bond, Loop and Joint Resistance Tester?

The electrical bonding circuit on an aircraft or vehicle provides a path through which unwanted current can flow. This can include current due to lightning strike or current leaking from faulty equipment. It is important that this current is routed away from people or equipment and can travel through a controlled bonding circuit to ground.

The primary aim of electrical bonding on an aircraft is defined as the establishment of a current path between electrical conductive parts, in order to assure electrical continuity allowing:

  • Prevention of electrical shocks
  • Fault detection
  • Flow/escape of electrostatic charge and leakage currents
  • Flow/escape of lightning current

Good electrical bonds across key structural and metallic components are essential, to ensure safe earthing, and to guard against damage from extreme events such as lightning strikes.

Looking for a loop tester suitable for explosive environments?

Introducing the ExLRT from MK Test Systems. It’s classified as Intrinsically Safe, it’s 30lbs lighter than the industry standard LRT and it’s approved by The Boeing Company.

Find out more

How MK Test can help

MK Test System’s BLRT loop resistance tester is an automatic computer controlled portable system and offers dramatic reduction in testing times by automating and simplifying the test process. Our BLRT systems have been specifically developed to replace the LRT loop resistance tester (906-10246-3; 906-10247-3; 906-10276-3), and are approved by The Boeing Company.

The BLRT offers bonding resistance measurement (DC), loop resistance measurement and joint resistance measurement.

Use the BLRT to perform simple, rapid and automatic test and measurement of:

  • Loop resistance and integrity of cable shields
  • Loop resistance and integrity of bonding straps
  • Joint resistance of any joint in the loop being measured
  • Bond resistance between structural elements.

The BLRT includes manual mode and automatic mode.  In automatic mode the user can download a test requirement and automatically create a test sequence. Measured values are analysed for pass or fail, retested if required, and test results delivered on a test report and uploaded to the user’s results archive, guaranteeing traceability. 

The BLRT is available in the following models: BLRT 1kHz, BLRT 200Hz.

To learn how simple the BLRT is to use, the Quick Start guide is available to download from our Knowledge Centre.

How does the BLRT compare against the LRT?

A detailed comparison between the LRT and our BLRT tool can be found here.

Not sure which Loop tester is right for you?

Read our comparison article, covering the main specification differences between LRT, BLRT and ExLRT loop resistance testers.

Compare loop testers

Approved by The Boeing Company

Our BLRT bond, loop and joint resistance tester is approved by The Boeing Company for use on unfuelled aircraft. The only alternative equipment authorised by The Boeing Company to conduct loop tests is the ‘LRT’ (models 906-10246-3, 906-10247-3 and 906-10276-3) which uses ageing technology, is cumbersome and prone to damage. MK Test’s BLRT was developed specifically to resolve the inherent issues with this legacy equipment, and we have worked closely with The Boeing Company to achieve this milestone approval.

“Through laboratory and airplane testing, Boeing has verified that loop and joint measurements are as accurate or more accurate as compared to the LRT on the same wire harness.”

“Boeing certified the BLRT for conducting loop resistance measurements on unfueled aircraft in December 2017. Boeing has added the BLRT to Boeing Tooling and Equipment Database.”

Boeing Service Letters 737-SL-05-022, 757-SL-05-009, 777-SL-05-009, 747-SL-05-011, 767-SL-05-010, 787-SL-05-007, 24th May 2019

For further details and clarification on usage, please refer to Service Letters 737-SL-05-022, 757-SL-05-009, 777-SL-05-009, 747-SL-05-011, 767-SL-05-010, 787-SL-05-007 on MyBoeingFleet or contact us.

Features and benefits


  • Integrated computer complete with MK Test management software
  • Paperless process
  • On screen graphical operator guidance
  • Automatic Pass / Fail of measured value
  • Automate the test process, saving time and gaining efficiency
  • Simple touchscreen control
  • User login and access control
  • Automatic logging and upload of test result
  • Guarantees traceability by user, UUT, measured results

Reliable & Accurate

  • Integrated self-test and validation toolset
  • Automatically recognition of probes and clamps to ensure correct tools used
  • Integrated automatic calibration and setting of gains and offsets
  • User can calibrate the BLTU and BLRT
  • Confirmed by The Boeing Company to be “as accurate or more accurate compared to the LRT.”

Active Probes & Clamps

  • Push button control enables full test control from the probes
  • LED pass fail indication on probes improves test efficiency
  • Integrated lights on probes for testing in dark areas
  • Various probe and clamp formats and sizes available

Lightweight and Robust

  • Single operator use
  • Lightweight
  • Battery powered and truly portable
  • Compact