Testing under vacuum

[bigben2k]

Nice find on the Temperature monitor. I've got a couple of Fluke 2190A and scanners; am working out a deal to acquire a spool of type T thermocouple wiring and some RTD sensors.

Yeah, budget is limited here too, otherwise I would have grabbed at least one of those NI cards. Right now it looks like it'd be quicker for me to build that 24 bit ADC circuit!

[Ice Czar]

anemometer array

I already can do temps, but being able to profile airflow and temps at the same time
now that makes me happy

here is your thermocouple wire guy
http://stores.ebay.com/AA-Appliance-...Q3amesstQQtZkm
BillA turned me on to him, I picked up 100' of type T

[bigben2k]

Yep, that's the one. I'm probably going to pick up the rest of that spool: ~185 feet.

Any idea if there are issues using stranded wiring to form a thermocouple?

[Ice Czar]

I would assume so,
consider that there isnt a uniform contact at the junction without say welding, even then it likely pretty unique
but under a screw terminal its all compressed together and just another electrical signal, I still would have perfered single wire like my J type extensions

my T type sensors are actually surface mount, imbedded surface mounts at that
(little blocks of aluminum) exactly how Im going to employ them Ive yet to detrmine without some testing, but Im thinking I'll machine them as needed and directly mount to various chips with a "cut" thermal epoxy. Need to get a few similar new surface sensors for comparative testing to determine response lag.

there was no going wrong for $20

the T type panel jacks and plugs (three prong w\ ground) from Omega will run over twice that,
plus sheilding, plus overbraid, plus the extension wire, but I have those already

[bigben2k]

Hum... I was wondering... if the Omega probes are "butt welded", maybe I could zap/fuse them together, using a high voltage source? What do you think?

I've never made my own thermocouples before, and I'm finding myself lost here. Worst case I can get real probes, and use that wiring for extensions.

[Ice Czar]

Ive had a thermocouple welder on my acquisition list for quite awhile, but they aren't all that cheap on ebay generally, and its not a very high priority, its factory automation and control engineering where they are doing hundreds per year Id imagine that it comes in handy, but then Ive also seen thermocouple "kits" with SS probes\wells, mineral insulation, and of course sensors.

The advantage there is you fabricate grounded, ungrounded ect packages yourself, but typically the sensor itself is factory made and you connect to it (which is where Id use a welder)

While I have no real idea of specifically what the difference would be between simply a wrapped vs welded vs factory fabricated sensor
I would assume its a closer repeatability with less error rate. and that a wrapped solution is a "close enough" general temperature type approach. Handmade welded sensors if they where subsequently calibrated and the error factor was coded into the aquistion system Id imagine would approach the same fidelity as a factory manufactured sensor that is consistently made from unit to unit in a more controlled manner. Simply with less error to plot those are "close enough" out of the box Id gues by at least a decimal place or two. (6.5 DMM)

Just a little dead reckoning

[bigben2k]

Looks rather simple, check out this oldie:
http://www.overclockers.com/tips437/

I'll make my own for the air measurements, for now.

This welder's insanely expensive:
http://www.tiptemp.com/Product.aspx?ProductID=4002
(TIG welder)

Another one, slightly cheaper:
http://thomasregister.com/olc/smartc...xtcolor=000000
with details here:
http://thomasregister.com/olc/17183047/twospec.htm
A 35 Vdc to 75 Vdc source, 250 Joules (watts/sec) capacitive discharge.

[Ice Czar]

since Bill is away I guess I'll need to play devil's advocate

as you are of course aware, we are now talking pretty small differences in one DUT vs another, and Id imagine that even though the primary path would be whichever two thermocouple metals are employed some of the path would be through the solder. Id also want an "ungrounded" sensor for directly embedding in a heatsink and or multiple surface mounts

used welders on ebay run $200>300
"as is" nasty ones occassionally much cheaper, that would still buy one hell of alot of bare sensors

I bought 40 epoxy coated and 40 glass rod thermistors the other day planning on building some "grids" with them that can be installed infront of, in back of and inside of cases \ fans. I'd be able to do 50 channels at a time with the 7701 (would need to build 2 cables)

close enough for rock and roll is really a function of what it is undertest, measuring airflow Im just trying to get a basic picture, but in WB tests there are alot of "photo finishes" which I think demands as high an accuracy as can be managed, there are alot of unaddressed variables still, and the "general picture" pretty well mapped already

[bigben2k]

I like the way you think

If I went the way of the solder (which still looks dubious to me), I would expect the solder to impact the response time of the TC, but otherwise nothing else. A big assumption...

I much, much favor the welding method, just because it's a simpler no-nonsense worry-free approach.

I just have to figure out something, somehow. We've posted links before, to spot welders. There's got to be an easy way to weld thermocouples. Google, here I come.

[Ice Czar]

if you want to know my real fear
its that the embedded chip cooling technology will change before we are really able to find an agreed on proceedure, IHS is just the first step, Im not even sure "waterblocks" as we know them are going to be that relevant for too much longer. There are so many developing technologies from Diamond Substrate Chemical Vapor Disposition to Carbon Nano advances in materials to nano heatpumps, dual phase microchannel and spray cooling that with the ever greater increases in power I think we are going to see integral thermal solutions sold with CPUs sooner rather than later. Intel's "waterblock" system was just the first. The IHS is basically a heatpipe base, its currentlty transferring to a seperate component but for how much longer? I think there will be a trend for the IHS to "grow" into a larger interface, that attaches to something else, possibly several options of something else.

remember alot of what drives thermal issues chip development comes from incresing densities in 1U and now blade servers
but once tooled into the fab gets transfered to the desktop

thats why Im really more interested in being able to determine the power consumption and develop a system that measures the total amount of heat whatever tech that is applied is moving to the case (or outside the case)
my "waterblock" test suite is really looking more to that direction. And I see vacumm insulation as an important part of quantifiying and isolating variables.

[bigben2k]

Got'em:

http://www.5bears.com/welder.htm
and
http://users.frii.com/katana/spotweld.html

[Ice Czar]

I wanted a spot welder. I nearly NEEDED one.

you cant link that here without also linking this
http://www.5bears.com/cnc.htm

everything duely bookmarked