Chip Temperature Measurement
Chip Temperature Measurement
(OP)
Hi,
We have been measuring the surface temperature of a problem chip using a thermocouple and an IR gun but are getting temperatures that are approximately 30 deg C different, the IR gun providing the higher reading. Other companies have been measuring this chip with a thermocouple and the results always conflict with the IR gun.
Anyone got any ideas why?
Thanks,
Mike
We have been measuring the surface temperature of a problem chip using a thermocouple and an IR gun but are getting temperatures that are approximately 30 deg C different, the IR gun providing the higher reading. Other companies have been measuring this chip with a thermocouple and the results always conflict with the IR gun.
Anyone got any ideas why?
Thanks,
Mike





RE: Chip Temperature Measurement
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Chip Temperature Measurement
Mike
RE: Chip Temperature Measurement
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Chip Temperature Measurement
I tend to agree that we don't have a reflection problem and there is no heat source to provide a problematic reflection. There is conformal coating on the chip however which is more reflective than the chip on it's own, I think I'll scrape some off as a test to see if that makes any difference.
Gunnur, we are measuring a fairly small chip, the chip casing is approx. 10mm x 6mm. Is this is size of chip not a suitable for using a thermocouple on?
Mike
RE: Chip Temperature Measurement
In case this applies in this case, generally when people start to argue about exactly how hot the chip is, the real answer is that it's simply too hot. That's a common organizational behaviour.
RE: Chip Temperature Measurement
IR camera's are great for monitoring an entire system, and will result with relative temperature differences between different parts of the system.
Thermocouples, TC's, are great for monitoring a few pin point locations in a system. TC's often result in a more accurate measurement. However, the obvious drawback with a TC's are that you need a TC for every location you want to monitor. Also, it is often very difficult to deduce the temperature in other portions of the system based on the data from a few discrete locations.
RE: Chip Temperature Measurement
The conformal coat might be sufficiently transparent in the IR to get you a reading that's closer to the desired measurement, but it might not.
At the very minimum, you definitely need to remove the conformal coat and do both measurements again.
TTFN
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RE: Chip Temperature Measurement
Mike
RE: Chip Temperature Measurement
So, if you have stainless steel pipes with molten chocolate running thru them all the time and you need to keep track of them, you can measure the temperature with contact then adjust the gun so that you can now walk thru the plant and correctly read your chocolate pipes.
If you have oxidized Al or anodized AL you should have no problem. Same with metal that has a dull finish.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Chip Temperature Measurement
Mike
RE: Chip Temperature Measurement
Sounds like you could use a thermal imagining camera. They work differently than the less expensive IR guns. I went to a cardboard factory with a salesman and when we were done the salesman whipped out a small handheld imager and showed it to the cardboard guy. He stuck his hand on the whiteboard for about 2 seconds then pointed the imager at the whiteboard. You could clearly see the hand print on the whiteboard in bright purple. You could then compare the color to a temperature color bar down the side, or you could move a cursor over the print and get a precise temperature value. He could also print out a color picture of any scene. It was pretty neat!
It was a Raytek of some sort.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Chip Temperature Measurement
RE: Chip Temperature Measurement
Most of the imaging IR sensors would have the same problem with water, since that's a property of the water itself.
There are some minor differences depending on the exact wavelength of the sensor.
Note also, that a measurement that's non-perpendicular to the surface will aggravate any anomalies with emissivity as well as reflections, particularly if the IR imager uses 3-5 um wavelengths. The Brewster angle of water in the 3-5 is sufficient high enough that serious glints from off-axis sources can show up.
TTFN
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RE: Chip Temperature Measurement
Here are some values for different materials:
http://www.monarchserver.com/TableofEmissivity.pdf
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"It's the questions that drive us"
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RE: Chip Temperature Measurement
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com