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Thermistor accuracy?

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maha_x

Member
Joined
Jul 25, 2001
Location
Rovaniemi, Finland
I just read this article (http://www.swiftnets.com/cpu_temp_testing.htm). Now my MSI K7T Turbo has a thermistor which is soft bending kinda (like those orange flat cables you might see on HDDs) and I even nodded some thermal goo on top of it so it makes perfect contact with the CPU base. How accurate can I consider it to be?

How about lapping the sink base? How much difference does it make?

Im also thinking changing my PSU fan to more silent and low powered. Old one is 0.24A with sleeve bearing... Will the power overheat? Now that depends on power consumption but how much? btw. Its 300W AMD cert.

Now some smart answers, thanks.
 

AMDGuy

Member
Joined
Apr 10, 2001
Thermistors vary in accuracy. There is no real answer to your question. I placed one of the digital temp probes from www.crazypc.com in my system and found my thermistor to be 2 degrees C off. This was after I bent the thermistor up to touch the back of the CPU. I suggest you order one of those digital probes also and implement the mod.

It's very simple to do, just trim some of the wire covering back and superglue the probe so that it touches the core, then mount the readout in a 5.25" drive blank. Hoot did a writeup on this some time back. You could e-mail him for details and pics. Be sure to test the digital thermometer before putting it to use. I got one that was off by 6C and had to send it back to crazypc.com for a replacement. They were very helpful with the exchange.
 

Thelemac

Administratively Deficient
Joined
Mar 15, 2001
It doesn't matter a whole lot how accurate the thermistor is...it just plain doesn't work right. It isn't measuring the temp of you core, it's measuring the temp of the back...which can also be affected by other heatpath cooling...leading to results that can be inaccurate to 5C or more. You CAN use it as a failsafe to make sure your cpu isn't about to meltdown or something, but as a measure of performance, it doesn't cut the cake. I would suggest AMDGuy's suggestion with the digital thermistor as being a good solution.

Lapping depends on the hsf. If it already has a smooth, flat bottom, it's not going to matter a whole lot (if any) but will definitely help on something rough.

On the fan issue, I wouldn't worry about it if you have some decent case cooling...otherwise you might wanna make sure you have a temp sensing fan.
 
OP
maha_x

maha_x

Member
Joined
Jul 25, 2001
Location
Rovaniemi, Finland
Thanks Colin. That's exactly what I was looking for. So I gues it just has to show much more than there really is... As relying on this measuring method I let it go up to 93C (95C being limit by AMD) before powering down... Whoops. Well, still works fine.

I gues I should drill a small hole to center of my orb under the fan, fill with thermal goo and insert heat probe. Not all the way through thought, to maintain maximum contact surface...
 
W

William

Guest
this is also why you should discount every single review you see that is using the in socket thermistor like some ot[h]er sites
 
OP
maha_x

maha_x

Member
Joined
Jul 25, 2001
Location
Rovaniemi, Finland
I think the ORB's clip is bad. As it has this circular "hole" which attaches it to the Heatsink (instead of the standard "on-top" clip) it never seems to sit perfectly on the core. Always somewhat tilted. New HSF is certainly a good idea...