AMPTEC Research · Failsafe Ohmmeters
620MC
Wide-range digital failsafe ohmmeter built for electro-explosive device testing
The Amptec 620MC is an intrinsically safe failsafe ohmmeter for igniters, pyrotechnic bridge wires, explosive bolts and similar electro-explosive devices. Its current-limiting circuit keeps the test current at 8mA or less on every range, and 4-wire Kelvin measurement gives an accurate reading while the device under test stays protected. Ordnance, aerospace and defense labs that need a wider top range than the 620A-4 reach for it. Evencat is the sole distributor for AMPTEC Research in Taiwan.
Overview
The 620MC is the wide-range member of the 620 series, built for resistance tests on squibs, flares, pyrotechnic bridge wires and other electro-explosive devices. It has five ranges: 20Ω, 200Ω, 2kΩ, 200kΩ and 20MΩ, read on a 4 1/2 digit LED display (19999 counts) with resolution from 1mΩ on the 20Ω range to 1kΩ on the 20MΩ range. The failsafe current-limiting resistor network keeps the test current under 8mA on all ranges, so a fault in the meter cannot fire the device. Nominal test current falls from 5mA on the 20Ω range to 0.010µA on the 20MΩ range, and the 4-wire Kelvin input with the OP-300 lead set compensates for lead resistance. The 620MC derives from the model approved by the USAF Nonnuclear Munitions Safety Board, is UL-913 compliant and is made by an ISO 9001:2015 certified manufacturer that NASA and the USAF buy from. Before ordering, decide whether you need the RS232C interface, continuous isolated power or a rack tray; all three are 620-series options.
Key specifications
| Ranges | 20Ω · 200Ω · 2kΩ · 200kΩ · 20MΩ (five ranges) |
|---|---|
| Accuracy | ±0.02% of reading and range (20Ω to 2kΩ); ±0.05% of reading and range (200kΩ); 20MΩ range ±2% of reading / ±0.2% of range |
| Display | 4 1/2 digit LED (19999 counts) |
| Resolution | 1mΩ (20Ω) · 10mΩ (200Ω) · 100mΩ (2kΩ) · 10Ω (200kΩ) · 1kΩ (20MΩ) |
| Maximum test current | Failsafe design, under 8mA on all ranges |
| Nominal test current | 5mA (20Ω range) down to 0.010µA (20MΩ range) |
| Measurement method | 4-wire Kelvin (OP-300 lead set) |
| Power | Four rechargeable 5AHr NICAD batteries |
| Dimensions | 9.75" × 10" × 3.25" |
| Weight | 3 lbs |
| Operating temperature | 0 to 50°C |
| Standards | UL-913 · ISO 9001:2015 |
Features
Failsafe current limiting
A failsafe current-limiting resistor network keeps the test current under 8mA on every range, so squibs, flares and pyrotechnic bridge wires can be measured safely.
Five wide ranges
Five ranges from 20Ω to 20MΩ, with ±0.02% accuracy on the ranges up to 2kΩ and ±0.05% on the 200kΩ range, cover both bridge wire checks and high-resistance measurements on igniters and blasting devices.
4-wire Kelvin measurement
Four-wire compensation through the OP-300 Kelvin lead set removes lead resistance, so accuracy holds at low resistance values.
4 1/2 digit LED display
A 4 1/2 digit LED display (19999 counts) resolves down to 1mΩ and is easy to read at a glance.
Rechargeable battery power
Powered by four rechargeable 5AHr NICAD batteries with the 620-DC charger supplied, for field and lab use alike.
Military and aerospace pedigree
Derived from the model approved by the USAF Nonnuclear Munitions Safety Board, UL-913 compliant, and in use at NASA and the USAF.
Typical applications
Defense munitions
Routine safety checks on non-nuclear munitions igniters
In munitions maintenance and flight-line work, technicians follow USAF Nonnuclear Munitions Safety Board practice and use the 620MC for acceptance measurements on squibs and bridge wire assemblies. The failsafe current limit (8mA maximum) means the test current can never fire the device, and the meter is built for hangar and field conditions.
Aerospace propulsion
Firing chain verification on rocket and satellite separation devices
During launch preparation, engineers use the 4-wire Kelvin input of the 620MC to measure firing chain resistance across five ranges from 20Ω to 20MΩ, confirming continuity of igniter cords and pyrotechnic devices and the integrity of every bridge wire, which gives NASA and commercial launch teams a solid basis for clearance.
Pyrotechnic products
Outgoing quality control on flares and signal cartridges
QC lines at pyrotechnic plants screen flares, signal cartridges and military pyrotechnic initiators with the 620MC at ±0.02% accuracy. The 4 1/2 digit LED display makes readings quick to judge, and within an ISO 9001:2015 system the results build a traceable batch record that rejects out-of-tolerance units and lowers the risk of accidental ignition.
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)
Transport and storage options
Interface, power and lead options
Downloads
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