Is this indeed a 10k thermistor? - Page 1
Forum section: electronics / beginners

author: XOIIO
author_rank: Super Contributor
timestamp: November 25, 2013, 04:25:34 am
content: I just copied and pasted this from the arduino forum, I figure you guys would have a better chance of knowing the actual part number of this thing.Hey everyone once and a while I have come across one of these tearing down UPS systems and other power supplies.I was wondering, is this indeed a 10k thermistor? At room temp it measured 80 oms, a bit warmer on my skin and it dropped to 78.9 ohms, I put it in a freezer for a short time and it went up to almost 90 ohms.It would be fantastic if this was a regular old 10k thermistor because I lost my zip lock baggie of them and will have to wait at least three weeks for some off ebay, but also because the plate with a screw hole which is exactly what I need. I was really hoping someone knows exactly which one this is and link to a datasheet, because I'd love to order some of these too for when I need the temperature of a heatsink or other metal surface, screwing it on would be way better than just pressing the usual style against the heatsink.

author: Udayan Sinha
author_rank: Regular Contributor
timestamp: November 25, 2013, 04:34:32 am
content: The resistance change is really small here...thermistors are supposed to be much more sensitive

author: David_AVD
author_rank: Super Contributor
timestamp: November 25, 2013, 04:38:54 am
content: The chance of it being a 10K thermistor are low considering it measures about 100 less in value at room temperature.

author: XOIIO
author_rank: Super Contributor
timestamp: November 25, 2013, 04:40:27 am
content: Quote from: Udayan Sinha on November 25, 2013, 04:34:32 amhmm, darn. Any idea what it would be then? my multimeter first read 16.92 nanofarads but now it just says overload. I'm just wondering why something like this wouldbe hooked to a big heatsink if not to measure temperature.Quote from: David_AVD on November 25, 2013, 04:38:54 amAh, I've never bothered to check the resistance of an actual 10k thermistor with my multimeter.Do you guys know of any that have this type of packaging?

author: David_AVD
author_rank: Super Contributor
timestamp: November 25, 2013, 04:42:51 am
content: Sometimes that packaging is used for diodes that are used in temperature sensing applications. Maybe try testing as a diode?

author: XOIIO
author_rank: Super Contributor
timestamp: November 25, 2013, 04:44:56 am
content: I've also come across a few of these, I'm sure these are temp sensors but no clue if it's a 10k or some other kind, I don't have it on hand to measure it right now, but maybe some of you have worked with them before.Quote from: David_AVD on November 25, 2013, 04:42:51 amthat gives me 0.062 volts.

author: sleemanj
author_rank: Super Contributor
timestamp: November 25, 2013, 05:37:17 am
content: Quote from: XOIIO on November 25, 2013, 04:40:27 amFor what it's worth, a 10k thermistor measures 10k specifically at 25 Degrees CHere's a lookup table I put together...https://docs.google.com/spreadsheet/ccc?key=0ArNRgk3zdvv3dEZpM0Rkb1AwWXJlN2V3X2ItdlhQRVE&usp=sharingOn the right of the table is also the formula to calculate (approximate) temperature from an arbitrary measured resistance.

author: XOIIO
author_rank: Super Contributor
timestamp: November 25, 2013, 10:17:40 am
content: just a side note, on ebay there are lots of 10k thermistors with those screw mounts, but it pretty much just looks like they were put inside a wire crimp, so I can pretty much just make it myself. I'll probably use a one wire temp sensor so I don't need to wait and do it that way.Anyways I guess I'll order some of these off ebay, first I'll find out their accuracy from the seller. The 1% ones are pretty much a buck each but I could get 50 of the 5% ones for 5 bucks as well which is kind of funny.edit: well, crap I have to put my project to the side since what I am measuring might get above 125 degrees. damn. I really wish I knew where those thermistors ran off to.

author: Neilm
author_rank: Super Contributor
timestamp: November 25, 2013, 06:27:07 pm
content: Any idea of the position in the circuit? I have seen thermal fuses that would react a bit like you have described.

author: XOIIO
author_rank: Super Contributor
timestamp: November 26, 2013, 08:30:58 am
content: Quote from: Neilm on November 25, 2013, 06:27:07 pmNot really, it was on the main heatsinks that had a lot of high power mosfets, power transistors and some diodes though.

author: Neilm
author_rank: Super Contributor
timestamp: November 26, 2013, 06:38:50 pm
content: Not much help I'm afraid. It could either be measuring the temperature of the heatsink as a thermistor, or it could be a thermal fuse - 100 ohms is a bit high for that but I've seen them around 65-70 so it is not out of the question.

author: jimmc
author_rank: Frequent Contributor
timestamp: November 26, 2013, 06:50:44 pm
content: I wonder if it's a PTC thermistor, try warming it to around 100C and see if the resistance suddenly rises.(below their 'trip' temperature PTC thermistors can have a negative tempco)Jim