I'm selecting my resistors for my Mini Metrology lab. In the instructions, Mr. Hoffman suggests measuring Tempco by using a warm bath of Mineral Oil. While messy, it would be quite effective. Here's the rub, I don't have mineral oil hanging around. I do however have air-duster which I can use upside down to cool the resistors under test. Since I'm looking for two resistors with the same lowest possible TempCo, would this work? Do resistors have a different TempCo going hot vs. going cold? Do I risk breaking the resistors? The datasheet
http://www.yageo.com/documents/recent/Leaded-R_MFR_2011.pdf says the resistors have an operating range from -55C.
You probably want a uniform steady state temp to take measurements, which you won't get with a can of freeze spray.
You probably want a uniform steady state temp to take measurements, which you won't get with a can of freeze spray.
You will if you empty the whole can into a container and immerse the board under test into the liquid.
On a related note, Ive seen a LED that was designed for 2.8A take 12A+ while it was on a MCPCB and submerged in a bath of freeze-spray/duster.
I'm selecting my resistors for my Mini Metrology lab. In the instructions, Mr. Hoffman suggests measuring Tempco by using a warm bath of Mineral Oil. While messy, it would be quite effective. Here's the rub, I don't have mineral oil hanging around. I do however have air-duster which I can use upside down to cool the resistors under test. Since I'm looking for two resistors with the same lowest possible TempCo, would this work? Do resistors have a different TempCo going hot vs. going cold? Do I risk breaking the resistors? The datasheet http://www.yageo.com/documents/recent/Leaded-R_MFR_2011.pdf says the resistors have an operating range from -55C.
You can use any oil, if you verify it's completely isolatingl
I'm selecting my resistors for my Mini Metrology lab. In the instructions, Mr. Hoffman suggests measuring Tempco by using a warm bath of Mineral Oil
Hi, I'm interested in what you are doing here and was wondering if you could point me to more information about this. I tried google without success
Thanks!
With regards to spraying your resistors with coolant, I have recently been measuring resistor values versus temperature. Not having any means to control temperature I have been logging values over the coarse of a day's temperature variation and have found that as the temp increases so to does the resistance but there is a massive lag as temperature drops.
I then applied heat from a heat gun expecting to see resistance climb dramatically but saw it drop substantially, almost as though it went from PTC to NTC. I haven't investigated further but one idea I had is that extreme temperature gradients may be causing thermoelectric voltages throwing readings off
but did it return to its normal value afterwards? otherwise you may have just slightly melted the film or windings depending on the type,
Yes it did return to nominal value. By heat gun I meant hot air reflow station, which I dialled down and measured around 150deg C on my thermistor prior to heating the resistor.
Good thought though and I'm open to any explanations
I found some baby oil and placed some in a small glass dish in a hot water bath. The baby oil got to about 45C. In the end, I found two resistors that were dead-on ( as far as I can measure) matched to each other, and both had a zero change when going from room temperature (22C) to the oil at 44C. So I think I found a pretty good pair.
Now on to final packaging.