A Safe and Quick Continuity Tester for Pyrotechnic Circuits
The BRIDGESAFE® continuity tester provides an ultra low test stimulus below 5mV (4mV typ.) with a short circuit current less than 0.5mA. Despite this exceptionally low output the tester can distinguish four resistance bands which are particularly suited to the SFX / Fireworks industries (which frequently make use of sensitive igniters with ~1Ω bridgewire and an ‘All-fire’ current ~1A). Firing circuit resistances above 20Ω are rarely encountered; low voltage firing systems capable of supplying 24V would have little margin to drive the ~1A sufficient to fire. The encounterd variety of system voltages, igniter sensitivities, and wiring configurations, lead to no perfect choice of indication ranges to suit all users, however the following five ranges have been selected for greatest overall usability.
- < 1Ω Suspiciously low: further investigation needed, or there may be a short circuit.
- 1Ω to 10Ω: the typical range for a single igniter circuit, or up to 3 igniters in series.
- 10Ω to 20Ω: a plausible resistance range for a series circuit, up to the maximum resistance for 24V firing.
- 20Ω to 200Ω Suspiciously high: further investigation needed to confirm if the circuit can be fired.
- > 200Ω shows no continuity indication.
For convenience 4mm ‘banana’ jacks are provided as the main test terminals and are compatible with a variety of off-the-shelf test probes and leads. User-created fixtures for bench testing and adapters for pyrotechnic articles containing a manufacturer supplied connector are compatible with minimum fuss. Bare leadwires can be touched against the protruding ends of the 4mm connectors for use without any additional accessories.
Although we are confident that the BRIDGESAFE® tester is safe to use on the majority of pyrotechnic systems, users are reminded that touching igniter wires to skin (which is likely to occur with this style of tester) can allow static electricity from the body of the user to discharge via the igniter, potentially cause an inadvertent initiation. Always risk asses any testing activity and consider the suitability of test stimulus, resistance range, and human-body electrostatic discharge. BRIDGESAFE® is not a suitable tester for shotfiring activities, and is not certified for use in mines. BRIDGESAFE® is not a suitable tester for explosive ordinance.