AMPTEC Research · Intrinsically Safe Igniter Testers
620RK
Mid-range intrinsically safe failsafe ohmmeter for bridge-wire explosive devices
The AMPTEC 620RK is a portable digital ohmmeter built for one job: measuring the resistance of bridge-wires, squibs, flares and other explosive devices without ever supplying enough current to fire them (NSN 6625-01-551-5511). A failsafe current-limiting resistor network keeps test current at or below 8 mA in every range, and the design descends from the 620A-4 approved by the USAF Non-Nuclear Munitions Safety Board. Ordnance, aerospace and munitions engineers in Taiwan reach for it when a standard multimeter is simply not allowed near the device under test. Evencat is the sole distributor for AMPTEC in Taiwan.
Overview
The 620RK continues the AMPTEC 620 line that started with the 620A-4, the model the USAF Non-Nuclear Munitions Safety Board approved for igniter testing. It uses 4-wire Kelvin terminals and a 4-1/2 digit LED display, updates 3 times per second, and covers three resistance ranges: 20 ohm, 200 ohm and 200 kohm. Basic accuracy is +/-0.02% on the two lower ranges. What sets it apart from a bench ohmmeter is the failsafe network: even under a component fault, the current through the igniter cannot exceed 8 mA, so an accidental initiation is engineered out rather than procedurally avoided. An RS232C interface (OP-232) and optically isolated power (OP-247) ship as standard, so the unit logs to a PC or runs on mains without compromising the intrinsically safe loop. The 620RK is UL-913 compliant, built under ISO 9001:2015, and in use at NASA and USAF facilities. Before ordering, confirm your bridge-wire resistance band falls inside 20 ohm to 200 kohm; if you also need to test devices with a series diode, ask us about the 620VL instead.
Key specifications
| NSN | 6625-01-551-5511 |
|---|---|
| Resistance ranges | 20 Ω / 200 Ω / 200K Ω |
| Accuracy | ±0.02% (20 Ω / 200 Ω ranges); ±0.05% (200K Ω range) |
| Resolution | 1 mΩ / 10 mΩ / 10 Ω |
| Nominal test current | 5 mA / 0.5 mA / 0.5 µA |
| Failsafe current | 8 mA (maximum) |
| Open-circuit voltage | 1.6 VDC |
| Display | 4½ digit LED |
| Update rate | 3 readings per second |
| Test terminals | 4-wire Kelvin |
| Temperature coefficient | ±0.002% per 1°C |
| Operating temperature | 0° to 50°C |
| Power | 4 rechargeable 5AHr NICAD batteries |
| Dimensions / weight | 9.75″ × 10″ × 3.25″ / 3 lbs |
Features
Failsafe current limiting
A current-limiting resistor network holds test current at or below 8 mA under any fault, so bridge-wires, squibs and flares cannot be fired by the measurement.
Three accurate ranges
20 ohm, 200 ohm and 200 kohm ranges with +/-0.02% basic accuracy and resolution down to 1 mohm.
4-wire Kelvin measurement
Kelvin terminals remove lead and contact resistance from the reading, which matters when the igniter itself is only an ohm or two.
LED readout, 3 updates per second
A 4-1/2 digit LED display refreshes three times a second, readable on a production line or outdoors in daylight.
RS232C and isolated power as standard
OP-232 RS232C interface and OP-247 optically isolated power ship in every unit, ready for data logging and ATE integration.
Battery-powered and portable
Four rechargeable 5AHr NICAD cells and a 3 lb package make it practical for field and depot work.
Typical applications
Ordnance maintenance
Pre-delivery safety acceptance of non-nuclear munitions and detonators
On a weapons assembly line or in a magazine before loading, technicians use the 620RK with 4-wire Kelvin leads to accept bridge-wire initiators by resistance, confirming each value sits inside specification without risking a fire. Test current drops to 0.5 uA on the top range, and the failsafe design follows the lineage approved by the USAF Non-Nuclear Munitions Safety Board.
Aerospace QA
Outgoing quality control of pyrotechnic devices (flares, explosive bolts)
NASA and commercial launch contractors check separation devices and escape-system flares at incoming and outgoing inspection with the 620RK, using the 200 ohm to 200 kohm mid ranges. The RS232C port records every lot to a PC so each igniter has a traceable reading before installation.
Hazardous sites
Field diagnosis of firing circuits inside ATEX hazardous areas
In Zone 1 and Zone 2 hazardous areas at petrochemical plants or mine blasting sites (ATEX EEX-9B-IIC-T4), blasting engineers run the battery-powered 620RK with no mains supply to confirm the firing circuit shows neither an open nor a short before the shot, cutting the risk of a misfire or an unintended fire.
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)
Hardware options
Downloads
Need pricing, specifications or lead time for 620RK?