Many years ago I read a Pease column in which he told the story of a client who was trying to design a DAC for the video display of an A4 or A6 aircraft. He had to do environmental testing but it wouldn't fit in the chamber, so he put it in a turkey roasting bag and did it in a regular oven.
It was a neat one, but I have never been able to find that column online. Of course I remember it every year at Thanksgiving.
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When I was fresh out of school an old timey engineer taught me a trick I remember every time I do a temperature test. He said (and I believe it is true) that more environmental tests cause failures not because of the temperature extremes themselves, but the rapidity with which we impose them.
Nothing wrong, he said, to let the temperature come UP or DOWN over the space of a couple of DAYS, but to go from the full hot test and then blow liquid CO2 into the chamber is sure to crack something.
Best thermal chamber I've ever used came from Sam's Club. They call it a beer cooler. Any size you want. Temperature UP comes from a 25 watt oven bulb. Temperature DOWN comes from a relatively small sealed package of dry ice sitting on a wooden platform above the DUT. Sensor is a small 1N4148 soldered to a solder lug and bolted to the chassis of the DUT.
Ya know, Michael, one of my problems here is that I frequently fail to add a smiley face to my comments. It appears to be a more serious thing than I originally imagined. I'll try harder. :)
Why do ignorant leftists hate me so? Do I say anything untrue about ignorant leftists ?:-) ...Jim Thompson
-- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
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| 1962 | I love to cook with wine. Sometimes I even put it in the food.
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