I have a conveyor oven that I would like to fairly accurately monitor the temp of objects as they pass under the last infrared panel. This is enclosed except for the conveyor belt "gates" that remain open to let the objects pass through.
The panels themselves sit about 4-6" off the conveyor belt and air is circulated via air knives. The panels are internally monitored for control and are about 800-1100 degrees Fahrenheit (currently it's set at 950). The ambient temps in the dryer aren't very high since its ir heat and it has an exhaust fan. I have a basic oven gauge hanging in there in a non-radiating area and I think it's seeing 150-180 degrees F. So it does get warm in there but not as hot as one might imagine with 950* panels radiating at all times.
I'd like to monitor about an inch in diameter unless it's possible to use an array... But ideally I'd like to sample from a 1" diameter are (or smaller) at any given time.
I've seen Melexis MLX90614 and the tmp0006 but I think field of view is the main issue there.
It would be cool to use the MLX90620 or similar and monitor the whole array as items passed under it being able to really see what is going on.
In the end I need to make sure the objects are hitting different temps, like 300-350* F.
This just needs a basic read out display and nothing fancy, so my main concerns and questions are finding the proper sensors that can live in the oven and monitor the area I need monitored. I probably need to be at least 3" off the surface of what is on the conveyor, maybe two min or have the ability to bend out of the way if something hits it on it's way through from time to time.
I've got k-type donut probes, thermal stickers and IR guns, but they are all telling me GREATLY different things. I'd like to get something permanently installed that I can rely on and trust to be accurate within a few degrees, even if it shows 320 when it's really 315 I can handle that. Just can't say 350 and it's really 300!
Any suggestions?
At those temperatures (800 - 1100oF), what material is your detector going to be made of?
Plastic is out and glass may also start to become soft, depending on its type.
Differential expansion (bi-metallic strip) or a sealed pressure vessel (as used in domestic ovens and refrigerators) may be your only answers, even though neither of them are accurate.
Henry_Best:
At those temperatures (800 - 1100oF), what material is your detector going to be made of?
Plastic is out and glass may also start to become soft, depending on its type.
Differential expansion (bi-metallic strip) or a sealed pressure vessel (as used in domestic ovens and refrigerators) may be your only answers, even though neither of them are accurate.
I guess I wasn't clear. The panels internal probe is set to stay at that temp, I'm guessing the surface of the panels are probably that as well. They are IR panels, so the oven isn't that hot. The thermometer that sits in between panels is only reading 150-180. The objects that ride on the belt get up to 350-400 max (not sure really because I don't have an accurate way to know). I will try to get that thermometer to just sit underneath the panel and see what it ends up reading. But my thoughts are to keep it out of the line of fire as much as I can and point at a slight angle. I'll look for where it might be a good place to put the sensor and put that oven thermometer and see how hot that area gets.
There are industrial IR temperature devices that might be worth looking at.
zoomkat:
There are industrial IR temperature devices that might be worth looking at.
http://www.harborfreight.com/non-contact-infrared-thermometer-with-laser-targeting-69465-8905.html
I have 3 of these... They all read fairly consistent between each other... but my K-Type reads WAY off from them, the temp strips are way off from them. Also not very easy/comfortable getting my hand in the oven to take readings.
I've pulled one apart to try and put the sensor inside the oven and wired up the display outside. The sensor had a lens and was cumbersome to try and keep together outside of that original housing. Didn't work in the long run.
Keep looking. I'm sure I've seen an instructable somewhere which pulled apart a cheap handheld IR thermometer and found a serial data pin that could be used by the Arduino. I think it was in a SMD reflow oven project.
Keeping the sensor cool but having it look at a hot object sounds like the best approach.
Not finding anything yet.
Was too busy outside the shop today to run my test, will try tomorrow.