Wowzers 10 C difference !!!

[zoopa_man]

I was messing around with my computer yesterday and had a cool idea. One of my case fans has a thermal sensor attached to it. I began probing my computer for the hottest place to cram this monster. Since it's temp range was form 30-85C with four different speeds depending on the temp. I though "well, the hottest spot is by the cpu it's self" So I crammed it down into the middle of my factory Intel heatsink that lives overtop my PIII 733. Since this is my main system and it's not over clocked my cpu runs anywhere between 22 and 30 C depending on the apps. I'm running. Much to my suprise when I booted up and went into my motherboard monitor I saw my temp immediately rise to 40C !!!! Wowzers, I just went 10C the wrong way!!! I opened the case and found a new home for the thermal sensor behind my
Geforce2 MX card. It's much happier there.
My theory is that the probe must have been blocking air form getting to the heatsink. If anyone else has any ideas on why my temps would rise that much let me know as I would like to get the thermal sensor close to the cpu but without having any affects on the temp. I know you guys always have cool ideas, so let me know. Thanks

 

[ken257]

I don't think the thermistor would block enough air that should be hitting the sink to make a differance. It is more likely that the air from the cpu fan was cooling the thermistor so that the thermistor controlled case fan never ran fast enough, as a result case temps went up which drove up the cpu temp.

 

[proze]

ken's got a good point, but even then, it'd have to be a helluva case fan to make a 10degree difference. you sure you didn't change anything else?

 

[zoopa_man]

I positive that's the only thing that changed. I was just messing arround with different options for the position of the probe.

 

[proze]

sounds kinda obvious, but maybe the probe was stopping the cpu hsf fan from spinning...? i've had that putting homemade probes under pII's little plastic coverings that fit over the heatsink on the stock hsf.

 

[zoopa_man]

It seems that there is some interest in this subject so I'm going to see if I can get to the bottom of this. We can play some Scooby Doo mystery solving. HEHEHE

I'll run a few different tests with the probe in a few different places. I'll jam it down to the bottom of the heatsink fins, try it under the plastic housing of the fan, stick it around the sides, and any where else I can think of sticking it.

I'll post results and then we can all do what we love best. Drink beer and ponder up ideas of what's going on.

I'm off to the testing station, will post results as soon as I get around to it. Thanks for your feedback. It is greatly appreciated.

 

[zoopa_man]

Ok, First let me say this is weird. I still have no solution to this but here's some numbers to stare at while we sip on our martinis.

Factory Intel heatsink / fan PIII 733 not OCed
each test was run for exactly three hours to insure a stable temp, room temp was average @ 20C only slight variation of 1C +/-

Room Temp 20C
No probe 24C
Probe loosely fit at bottom side 25C
Probe stuffed into middle bottom of heatsink 40C
Probe on HS plastic housing - 25C

As you can see with the temp probe stuffed to the bottom of the HS directly over the die there is a huge effect on temp. I made sure that the fan was not being blocked and was running normally so I ruled out that thought. What's going on here? Is it possible that the sensor is blocking heat form traveling up the fins where it is crammed in ? I'm baffled. At least I know where not to stick it.

 

[seadog]

I know this sounds crazy, but it almost seems like your monitor is reading the temps off the probe you are moving around.

 

[zoopa_man]

Something I should add to help clear some things up. The probe I took the readings form is built into my gigabyte motherboard. I bent it up slightly to insure a good contact with the bottom of the cpu.

The probe that I was moving around was connected to an ernemax fan that has variable speeds depending on the readout of the probe. 20c - 80C hotter the temp faster the fan. I set it up so that the fan wasn't affecting the system. Meaning it was outside the case and had no way of blowing air into or out of the case to effect cpu temps.

 

[proze]

this is wierd... i think you're right, though.. you know where not to put it ^_^, so maybe you should leave it at that! ;-)