AMPTEC Research · Intrinsically Safe Explosion-Proof Ohmmeters
620UK-V4
4-wire intrinsically safe digital safety ohmmeter for ultra-safe resistance testing in explosive and volatile atmospheres
The Amptec 620UK-V4 is the portable EEX digital safety ohmmeter you take into the hazardous area itself. It uses a 4-wire (Kelvin) measurement so bridge wires, squibs, flares and other initiators are read without lead resistance in the result. A failsafe current-limiting network keeps the test current under 8 mA under any fault, and the design meets the EU ATEX Directive, intrinsic safety standard EEX-9B-IIC-T4 and USA MIL-STD-810. Defense, ordnance and munitions labs choose it when they need low-ohm accuracy and certified safety in the same box. Evencat is the sole distributor for AMPTEC Research in Taiwan.
Overview
The 620UK-V4 is the 4-wire successor to the 620UK. Both are portable EEX ohmmeters built for resistance testing on explosive devices where the atmosphere may be volatile, and both carry the same certifications: EU ATEX, EEX-9B-IIC-T4 and USA MIL-STD-810. The difference is the Kelvin input. Four-wire sensing removes lead and contact resistance from the reading, which is what lets the meter hold ±0.02% of reading accuracy on its best ranges. Seven ranges run from 2 Ω to 2 MΩ. What makes the instrument safe is what it cannot do: a current-limiting resistor network holds the output at 8 mA or less even if an internal component fails, and the open-circuit voltage stays below 1.4 V, so a squib or bridge wire is never fired by the measurement itself. The unit runs from four AA alkaline cells and reads out on a 4 1/2 digit LCD. Before ordering, decide which lead set you need: the standard package ships with the 620UK-304V4 banana jack set, and gold-plated Kelvin clips or mini spear probes are available for small or awkward contacts.
Key specifications
| Resistance ranges | 2.0 Ω / 20.0 Ω / 200 Ω / 2.0 KΩ / 20.0 KΩ / 200 KΩ / 2.0 MΩ |
|---|---|
| Nominal test current | 5 mA (2 Ω to 20 Ω), 0.5 mA (200 Ω), 50 µA (2 KΩ), 5 µA (20 KΩ), 0.05 µA (200 KΩ), 50 nA (2 MΩ) |
| Failsafe current | 8 mA (2 Ω to 20 Ω), 1.5 mA (200 Ω), 150 µA (2 KΩ), 15 µA (20 KΩ), 1.5 µA (200 KΩ), 150 nA (2 MΩ) |
| Maximum failsafe current | 8 mA |
| Accuracy | 2.0 Ω range: ±0.02% of reading, ±0.05% of range; 20 Ω to 20 KΩ ranges: ±0.02% of reading and range; 200 KΩ: ±0.05% of reading and range; 2 MΩ: ±1.0% of reading, ±0.2% of range |
| Open-circuit voltage | <1.4 volts |
| Display | 4 1/2 digit LCD |
| Measurement terminals | 4-wire (Kelvin), 5-pin Amphenol connector |
| Update rate | 3/sec |
| Accurate temperature range / operating temperature | 25° ± 10° C / -20° to 40° C |
| Power | 4 x 1.5V AA alkaline batteries |
| Dimensions and weight | 7.69" x 7.56" x 3", 5 lbs (10 lbs shipping) |
Features
Intrinsically safe, failsafe by design
Meets the EU ATEX Directive and intrinsic safety standard EEX-9B-IIC-T4, and is qualified to USA MIL-STD-810, so it can be used inside explosive and volatile atmospheres.
Current limit protects the device under test
The failsafe network caps the output at 8 mA and holds the open-circuit voltage below 1.4 V, so squibs and bridge wires cannot be fired by the meter.
4-wire Kelvin measurement
Four-wire sensing removes lead and contact resistance, which improves both accuracy and repeatability on low-ohm bridge wires.
Wide range, high accuracy
Seven ranges from 2.0 Ω to 2.0 MΩ, with ±0.02% of reading accuracy on the best ranges, cover the tolerance checks that ordnance and pyrotechnic testing demand.
Clear digital readout
A 4 1/2 digit LCD updates 3 times a second and flashes on overload, so the state of the reading is never in doubt.
Battery powered and portable
Runs on 4 x 1.5V AA alkaline cells; the case measures 7.69" x 7.56" x 3" and weighs 5 lbs, light enough for field and site work.
Typical applications
Aerospace and defense
Resistance verification of pyrotechnic ignition circuits
During production and preparation of rocket motors, missile fuzes and satellite separation devices, engineers measure bridge wires, squibs and pyrotechnic initiators to confirm the firing circuit is intact. The 620UK-V4 caps the test current at 8 mA and is intrinsically safe, so the measurement cannot fire the device. NASA and the USAF use the family for mission-critical checks.
Hazardous area field work
Routine safety checks in ATEX hazardous areas
In magazines, ammunition lines and energetic-material plants where explosive dust or flammable gas may be present, regulations require test equipment to carry EU ATEX (EEX-9B-IIC-T4) and UL-913 intrinsic safety approval. With an open-circuit voltage under 1.4 VDC and seven ranges, the 620UK-V4 lets operators check initiators without leaving the zone, cutting downtime and keeping the site compliant.
QC and acceptance
4-wire measurement for production quality control
In acceptance testing of munitions and aerospace initiators, the 4-wire (Kelvin) connection removes lead resistance and the ±0.02% of reading accuracy lets inspectors sample low-ohm bridge wires batch by batch, confirming each initiator sits inside its tolerance. The readings become traceable quality records that support ISO 9001:2015 process audits.
Options and configuration
Tick the options you need. We compile the configuration into a list and carry it into the quote form.
Standard package (included)
Test lead and probe options
Transport and storage options
Downloads
Need pricing, specifications or lead time for 620UK-V4?
Also available for rent: 620UK-V4 is part of the AMPTEC rental program, for project peaks, calibration backup and pre-purchase trials. Rental inquiry →