OK, so what is the LOWEST resistance you've ever measured for an igniter?

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cvanc

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Hey troops-

So we often talk here about how a high resistance value is a sign of a bad igniter. But of course the other end of the scale can tell us something too. So - for those of you who have actually measured igniters with a decent meter - what is the LOWEST value you've ever read and what type of igniter was it?

Just to be clear we're talking normal healthy igniters here, ones that you would expect to work.

In my experience the good ol' Estes igniter is pretty darn low at 0.9 or maybe even 0.8 ohms. That's pretty far down there.

What have you measured? Is there any type that reads lower than the Estes?

With enough data points we might be able to clearly bound a lower limit for good/bad sorting. Thanks!
 
First off you need a digital voltmeter that can accurately read low resistances. On many VOMs 1 = 0.

Second, you should know what the resistance of your igniters should be. Once you know that then the acceptable is probably not more than a factor of 2 from the nominal resistance. For example, a nominal 1 ohm igniter should read between 0.5 to 2 ohms or closer to the nominal value.

Third, download the wiretron resistance calculator, and use it to calculate the approximate resistance of your igniters.

Bob
 
Good info bob. I was just being silly on my post in case that wasn't clear.
 
There is some seriousness behind the answer.
Some Altimeters's continuity check is good enough to recognize the difference between a dead short and a 1-ohm e-match....
Would be interesting to know the real distribution of resistances in the field.
 
Remember that the length of the lead wire counts too, since we're talking very low values here. For example, DaveyFires with the full 2m leads normally measure about 2.2Ω, but when the leads are cut short for actual use, that drops down to 1.9 or lower. As Bob Krech said, the valid values are different for each brand.
 
Good old nichrome wire is really low from when last time I used it 20 years ago.
 
Are we talking motor igniters (the OP mentioned Estes) or altimeter deployment lighters? If the former, then a different forum, say Propulsion, may be a better place for this thread?
 
When I did homemade ematches with made-from-scratch pc board blanks and 40ga nichrome it would depend upon how well I got the nichrome to solder to the board. Anything above 2ohms with long leads were suspect. If fact I had way more failures with commercial ematch blanks and I have no idea why. The commercial blanks used finer wire plus I didn't run solder almost all the way out to the end like the commercial blanks looked like.

I did see some of mine test 5 to 12 ohms which of course I wouldn't even bother to consider for a rocket. The 1 to 2ohm jobs would pop with a partially discharged 1.5V battery. Am I using my own matches on rockets? Heck no! Not with the commercial alternatives available now. I wanted to be ready in case ematches were going to dry up and blow away from us common "rocket folk". It was an off and on 4 year odyssey of learning plus I had a neat bench shear for making the PC board chips and only had to get a small amount of the reagents. It's not worth the trouble and time to make ematches. Kurt
 
I'd like to resurrect this thread. I've been evaluating igniters for an airstart project and have noticed that there is a wide variation in resistance. I'm evaluating commercially available igniters from QuickBurst and other sources. For example, three of the QB Fat Boy igniters (for K - M motors) measured 5 ohms, 1.3 ohms, and 4.3 ohms. Two QB Slim Gems (H - K motors) measured 63.4 ohms and 24.5 ohms. I have also tested a large number of the MJG and J-Tek igniters (aka e-matches) from Electric Match and all are within a very close variation of 0.8 to 1.2 ohms.

I'm using a high quality ohm meter calibrated to a 1 ohm standard so the meter is not in question. What accounts for the variation? Should I plan on using the Electric Match igniters and pyro dipping them for use as high power motor igniters? All opinions are appreciated.
 
Jackman, exactly what meter do you have and more importantly what leads are you using?

I have no experience with the lighters you mentioned but I would be concerned about such wide variations in resistance. I would ground test a quantity of them using the battery source they would see in flight. The only way to know if all these various resistances actually work is to prove it to yourself. Good luck.
 
I'm using a high quality ohm meter calibrated to a 1 ohm standard so the meter is not in question.

Is that a high quality four wire meter? If not then you are also measuring wire and interconnect resistance. Not a big deal in most cases but down around 1 Ohm it can be a problem. But be careful. While I have seen some reasonably priced four wire meters for sale their test currents were too high to be safe. For safety and accuracy you need a purpose built igniter tester. Which are expensive although I see a few Valhalla testers on Ebay but who knows what condition they are in.
 
I bought a dirt cheap meter that has a 200ohm setting on it. Surprisingly, the commercial matches rarely were out of spec. In fact I can't remember ever reading one out of spec with this cheap meter.
I don't bother measuring anymore and just use a continuity tester.
My own matches were another story and getting the bridge wire soldered properly was the issue. Get the reading 1.2 to 2ohms and the matches fired many times with a AAA cell. I ground fire a few of my old ones and a fair number don't pop. They flare and burn which I think is desirable. Kurt
 
I bought a dirt cheap meter that has a 200ohm setting on it. Surprisingly, the commercial matches rarely were out of spec. In fact I can't remember ever reading one out of spec with this cheap meter. I don't bother measuring anymore and just use a continuity tester.
My own matches were another story and getting the bridge wire soldered properly was the issue. Get the reading 1.2 to 2ohms and the matches fired many times with a AAA cell. I ground fire a few of my old ones and a fair number don't pop. They flare and burn which I think is desirable. Kurt

That confirms my observations, Kurt. I suspect that the igniters that I've tested are made by hand with less than perfect QC. Those made by Electric Match are made for the pro industry and subject to better testing and QC.

And no, I'm not using a 4 wire measurement method. I'm using a DMM and my trusty (probably before your time) Simpson 260 VOM with R x 1 scale. I'm not looking for decimal point accuracy in my readings. I calibrate (zero out) the Simpson to subtract the resistance of the meter leads and measure against a 1 ohm 1% resistor. Using the DMM I subtract the meter leads from the reading. There's good agreement between the meters. Furthermore, I have 4 of the 1 ohm 1% resistors to model the cluster. All of the resistors measure in good agreement. The measurements are gross indeed but good enough for this purpose.
 
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my trusty (probably before your time) Simpson 260 VOM with R x 1 scale.

I haven't used Simpson 260 since I was in the Navy in the '80s. I measure all my matches with a Radio Shack analog VOM I got back in the '80s. I don't have the precision resisters to calibrate it with, but as you said, being able to zero the meter to take the leads out of the equation makes it much better then my DMM for low ohm tests.
 
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