Igniter temperature sensing

I'll bet you can find something, but I'll also bet that it won't be cheap. When you think that it's got to be able to sense temps going for room temp to 100's of degrees in a small amount of time, reading at that interval could be a problem, and you need a sensor that won't get fried... Plus, you're probably looking at a thermocouple to read the temp, they tend to be slow in responding.

Now, if your looking for a way to measure something like "how long after I apply current will the igniter fire?" , you might be able to do that with an oscilloscope... Trigger when voltage is applied, and trigger when a "burn thru" is detected at the igniter head (a wire with a low voltage applied "burns thru" due to the igniter igniting) Then measure the time between the two triggers...

The challenge is something with a high enough sampling rate for the typical burn time of an igniter, coupled with a thermistor that won't be destroyed by the ignitor, or something that you're willing to treat as disposable.

-Kevin

You need an infrared sensor mechanism -- you don't need to worry about frying the temperature sensor that way -- and yes, it's do-able, but not as simple as you would think..

David Erbas-White

Are you refering to the oscilloscope deal? Why an IR sensor? If you're just looking for a pulse, a "burn-thru" will work.. The leading pulse of the burn thru would be enough..(even without any de-bounce).

"hot enough to burnthru is hot enough to ignite motor" could be the plan..

Granted, it might take some trials to figure out what's best to use for "burn thru", but it could be the actual bridgewire of the igniter itself! (one trigger -apply power and wait for power drop, and measure the time between.). If the pyrogen burns, you got the ignition time! (My IR sensor would be what I see! The pyrogen doesn't fire, bad test!). This doesn't need to be ISO, as it was requested to be "cheap and simple"! ("burnthru wire will "burnthru" at 750 degrees, so it took x time to reach that point. A piece of solder could do it, as solder often has a rated melting temp....)

Woody, et al,

I've seen some igniters vendors who claim high burn temps (e.g. 3500 F), presumably as a metric for how well they can ignite the nearby AP. So I was wondering how one could test home-made igniters to see how they compare, especially trying out different "mixes". So I wasn't going for burn-through time - yes I could easily rig up something to measure that.

As David suggests, I was hoping to find an IR sensor that could handle the high range of possible temperatures - ideally hooked to a serial port with logging s/w, so as to keep the h/w cost down. Have been googling, but so far so solid (inexpensive) leads.

Many moons ago, I did an IR sensor design - but I don't think I still have the data - and I've had a really rough day so I'm not thinking straight.

If any of the information comes back to mind, I'll post it here - but again I warn, it's a lot more difficult than one would expect at first...

David Erbas-White

One could also do rise time tests on a known hard to light propellant (ie old blackjack).

Jerry

I did this test:

Doc

Magnesium by itself burns at a temperature around 4000 degrees F. With the addition of a strong oxidizer this temperature will increase to well over 5000F. It works along the same principle as a blacksmith using a bellows pump to blow air on burning coal to greatly increase the burn rate and thus increase the temperature of the burning coal. Check out the link below for more specific information about the properties of magnesium.