AMPTEC Research · Bond Resistance Testing
620LK-HR
High-resolution four-wire bonding ohmmeter spanning 20 mΩ to 20 Ω
620LK-HR is the high-resolution version of the AMPTEC Research 620LK, a four-wire bonding ohmmeter for metal-to-metal joints. It keeps both standard 620LK ranges and adds a lower 20 mΩ range and a higher 20 Ω range, with resolution down to .001 mΩ. AMPTEC first built it to a Lockheed Martin requirement. Aircraft maintenance shops and commercial airlines choose it when the bond limit is tight enough that a standard meter's last digit is no longer enough.
Overview
AMPTEC Research 620LK-HR is a high-resolution four-wire bonding ohmmeter for metal-to-metal bond resistance. It covers four ranges, 20 mΩ, 200 mΩ, 2 Ω and 20 Ω, each accurate to ± .025% of range, with resolution down to .001 mΩ on a 4 1/2 digit LCD. Each range drives a controlled nominal test current, from 1 A down to 10 mA, through a four-wire connection, so lead and contact resistance drop out of the reading. The meter is UL-913 compliant and built under ISO 9001:2015. It was designed for Lockheed Martin and belongs to the same family of AMPTEC safety test instruments that aircraft maintenance shops and airlines already rely on. An internal rechargeable battery pack powers it, and the 3 lb unit is easy to carry to the aircraft. Note that this model charges from the HR-DC charger rather than taking AA cells, so plan for the charger and a padded case when you configure it.
Key specifications
| Ranges and nominal current | 20 mΩ (1 A) / 200 mΩ (100 mA) / 2 Ω (100 mA) / 20 Ω (10 mA) |
|---|---|
| Resolution | 20 mΩ: .001 mΩ; 200 mΩ: .01 mΩ; 2 Ω: .1 mΩ; 20 Ω: 1 mΩ |
| Accuracy | ± .025% of range (all ranges) |
| Temperature coefficient | ± .0025% per 1° C |
| Display | 4 1/2 digit LCD |
| Update rate | 1 reading per 3 seconds |
| Max. internal voltage | 5 VDC |
| Max. input voltage | 250 VDC |
| Terminal type | Trident |
| Operating temperature range | -20° to 50° C |
| Power | Internal rechargeable battery pack |
| Dimensions / weight | 7.69″ x 7.56″ x 3″ / 3 lbs |
Features
High-resolution four-wire measurement
Four-wire connection removes lead and contact resistance from the reading; resolution reaches .001 mΩ for demanding metal-to-metal bond tests.
Four ranges end to end
All the standard 620LK ranges plus a lower 20 mΩ and a higher 20 Ω range, so one meter covers milliohm bonds and ohm-level checks.
Accuracy and stability
± .025% of range on every range and a temperature coefficient of only ± .0025% per 1° C keep readings consistent across sites and seasons.
Safety compliance and quality system
UL-913 compliant and made under ISO 9001:2015, from the same line of AMPTEC safety test instruments used across aerospace.
Clear digital readout
A 4 1/2 digit LCD updates every 3 seconds, so the bond value is read directly at the joint.
Portable for field work
Internal rechargeable battery pack and a 3 lb unit weight, easy to carry into the maintenance hangar or onto the aircraft.
Typical applications
Aerospace manufacturing
Aircraft structural bond verification
When verifying bonds on fuselage skin, wing structure and ground strap points, 620LK-HR resolves 0.001 mΩ at ±0.025% accuracy. That is enough to prove a bond sits under the very low limits in standards such as MIL-B-5087, so static charge cannot build up and ignite a fuel tank or weapons bay.
Defense metrology
High-accuracy bond measurement to military standards
620LK-HR began as a Lockheed Martin requirement for military platforms. On missile systems, weapon pylons and ground support equipment (GSE) it operates safely in potentially explosive atmospheres with a MIL-STD-810F environmental design and UL-913 intrinsic safety, while offering twice the resolution of the standard 620LK for demanding metrology audits.
MRO
Scheduled electrical bond checks in MRO
During heavy maintenance (C and D checks) engineers use 620LK-HR for four-wire Kelvin measurements on antenna mounts, static dischargers and fuel system bond straps. The internal rechargeable pack and -20°C to 50°C rating let it work on the ramp or in the hangar, and the readings are filed as airworthiness compliance records.
Options and configuration
Tick the options you need. We compile the configuration into a list and carry it into the quote request form.
Standard equipment (included)
Probe and test lead options
Accessory options
Downloads
Need pricing, specifications or lead time for 620LK-HR?
Also available for rent: 620LK-HR is part of the AMPTEC rental program, for project peaks, calibration backup and pre-purchase trials. Rental inquiry →