How long is the current delivered on a Telmetrum, Easymini, or other Altus Metrum products to the ematch output terminals? Is it dumping full battery voltage, or just a bit under battery voltage? I guess I could hook up my scope, but I'm lazy, so I' thought I'd ask. I'll get out the scope if I have to.
The reason I ask is I was trying to come up with something I could use for testing computers in my "test dummy" rocket. Let's say I wanted to test a Telemetrum, Altus Metrum or other rocket computer product by putting it through a flight without actually using it for ejection. Rather, if I use other ejection method (like direct motor ejection) and connect the computer in a protected AV bay compartment to something like a small fuses to mimic ematches that would blow when it got voltage applied, this would indicating it did send current to the output. (Wouldn't tell me when it fired, but would indicate it was working in some fashion. The log file would tell me when it fired. ) I could always use an actual ematch for the test, but then I've got something combusting inside a tube with no actual ejection going on. The test area is isolated from the computer compartment.) I could make my own ematch with no pyrogen on it, but I'm trying to keep this simple with off-the-shelf parts and without actually combusting something. A small glass fuse with visual indication would be a great choice. I bench tested my Telemetrum with a pico fuse I had on hand (.062A), but the fuse never popped. A .062A Pico II fuse has a 7 ohm internal resistance. It was connected directly to the Telemetrum's terminals. On paper, it sure seems like it should have popped, but perhaps I'm making a bad assumption on a technical detail. If I assume I get 3 volt at the terminals; according to the Pico II fuse spec sheet, it should pass 428 mA (3V/7 Ohm) and pop in less than 1mS, but it didn't. Something like a 300 mA glass fuse has a lower internal resistance at about 1.6 ohm and would give me a visual indication. If I assume the same 3 volts across the terminals during ejection, I should get 1.8 amps across a 1.6 ohm, which should blow a 300 mA glass fuse in less than 20 mS. But I'd need to know the actual voltage across the terminals and for how long it fires. The Telemetrum fires an actual ematch with no problem in a bench test. Pico Fuse spec sheet http://www.littelfuse.com/~/media/electronics/datasheets/fuses/littelfuse_fu se_251_253_datasheet.pdf.pdf Glass Fuse spec sheet https://www.parts-express.com/pedocs/specs/fast-acting-fuse-235p-series-spec ification-sheet-specifications-45682.pdf Scott Myers
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