heat die dimensions - a public worklog

[BillA]

the intent of this worklog is to develop a dimensioned drawing for a heat die reflecting present industrial practice
- while there is nothing to prevent a DIYer from making and using such a device, the required resources may be substantial
- while this is a specific activity of myself/CoolingWorks, it is hoped that a general consensus might result in an open design available to anyone wishing to utilize such
(Ben jump in here - but not your WBTA please)

the general configuration of a heat die is well understood as can be seen in this old Aavid paper
http://www.aavidthermalloy.com/technical/papers/pdfs/packaging.pdf
and there are recent papers in the last several years by both Intel and IBM describing the same configuration
-> and most notably is the 'amazing' work to the same point by 'our' Incoherent (3 cheers !)

there is nothing magical about heat dies, different designs properly executed can yield valid and comparative results as this paper by Sun illustrates
http://www.electronics-cooling.com/html/2005_feb_a2.html

as most here know, a heat die is 'also' a TIM joint tester and it is well to be aware of industry practice, progress, and goals;
such can be seen here http://www.electronics-cooling.com/html/2003_november_a2.html
and a TIM joint appraisal here http://www.electronics-cooling.com/html/2003_november_a1.html
and here http://www.electronics-cooling.com/html/2004_february_a1.html

thermal test dies and dimensions of contact areas are reviewed here
http://www.coolingzone.com/Content/Library/Papers/Sep%202000/Article03/Sep2000_3.html

the above list is not complete, but sufficient to understand that our efforts are not in a vacuum; we do not need to reinvent the wheel (and lack the resources too, eh ?)

I have a question not addressed in the above papers:
Assuming a calorimeter type sensor placement, what is the necessity to use copper for the heat die ? (i.e. does the matl's conductivity matter so much ?)
while Ben's suggestion to use iron seems radical, why not use a more durable material ?

It seems apparent that the size/configuration of the testing heat source must be related to the actual source size; and the wear of the copper face introduces an known and unacceptable variation in the test results (limited initial degradation progressing at an ever increasing rate).

regarding the face dimensions, I'm inclined to start with 2 sizes, 10x10mm and 12x12mm - based more on current desktop CPUs than any trend

and for the heat source 2 heater cartridges in the base

comments solicited

[jaydee]

Glad you started this thread.

I am working on a drawing of what I was going to build based heavily on Incoherents work. Will post when finished.

As for the material to use the main reason I went with copper is because the block material is usually copper. If you use something harder the chances of damaging the base of the water block increases with multiple remounts. Steel would be a very very bad thing to use IMO. Copper, aluminum or brass were the only materials I was going to use. Stuck with copper for conductivity reasons, maybe not relevant though?

The main problem I have with heater cartridges is finding a low ohm version. I would prefer them at 5-10 ohm but very hard to find them under 100ohm...


Anyway hope this thread takes off.

[BillA]

await your dwg

for years HSFs were put on silicon, don't see hardness per se as limiting - has very much to do with the mounting procedure and force applied
- but a sharp corner and a tilted mount will cause damage; to the die if made in copper and to the HSF if made in steel
-> as the die is vastly more expensive, I would opt for protecting the die

eventually you will understand that you need a big linear psu

[jaydee]

Here is some pics of my first drawing (and only drawing so far). I went with 1/2" die just for convenience and can easily be changed. Note the holes for the probes are .25" deep. The 4 holes on the outside sides are meant to be tapped for screws to keep the cartridges tight. I was planning on using 1" long and 1/4" wide 100watt 120V cartridges available at mcmaster.

What other materials would you suggest we look at?

[BillA]

re the dwgs:
- set screws on bottom to push up
- use 1" stock for more thickness on bottom (if not copper ?)
- decrease length to 1.25" if 1" cartridges are used
- use two 200W AC heaters

what was/is the basis for your sensor to sensor to face dimensions ?
noting that the 2ed sensor to face dimension will change over time (reworking) if of copper

someone have experience with calorimeters ?
what is the trade-off with 2 sensors vs. 3 ? (2 points a line, 3 a curve - no ?)
Incoherent, have you looked at this ? (did I miss a previous discussion ?)

a material ?
Silicon Carbide, SiC ?? ( some info http://www.accuratus.com/silicar.html)

[jaydee]

re the dwgs:
- set screws on bottom to push up
- use 1" stock for more thickness on bottom (if not copper ?)
- decrease length to 1.25" if 1" cartridges are used
- use two 200W AC heaters

what was/is the basis for your sensor to sensor to face dimensions ?
noting that the 2ed sensor to face dimension will change over time (reworking) if of copper

someone have experience with calorimeters ?
what is the trade-off with 2 sensors vs. 3 ? (2 points a line, 3 a curve - no ?)
Incoherent, have you looked at this ? (did I miss a previous discussion ?)

a material ?
Silicon Carbide, SiC ?? ( some info http://www.accuratus.com/silicar.html)
- Set screws! That's the term I was looking for. No problem on changing that to bottom.

- I was assumining we wanted as little material as possible but if not I can easily add more to the bottom. Would benifit the set screws aswell.

- It is 1.25" no?

- If 2 - 200 watts heaters are recommended I would have to go with 1.5" long.

Sensor holes were based on ease of drilling more than anything else. To close to the top or bottom would be hard to drill.


Not sure on the rest. Will change things as suggested.

Silicon Carbide looks pretty good. Were can it be bought and how easy is it to machine?

[BillA]

er, strictly diamond tooling I believe
SiC are cutters, no ?

way big $ for a chunk I'd guess, Monday I'll source some
I have phenolic BTW if you need a piece

note that what we are doing will 'work' with any material

[RoboTech]

I still find brass interesting (my first thermal die sim was brass, but later versions have all been copper)

+Thermal conductivity similar to silicon
+Tougher than copper (more robust surface area)
+Easy to machine, readily available
+Relatively good thermal conductivity
- Main body will run much hotter for a given die surface temp than copper, especially when incorporating a calorimeter tower section. This will produce much greater heat loss to ambient. Can be easily accounted for though by running a heat loss calibration curve.

[BillA]

good suggestion Lee
silicon bronze is tough stuff too
I'll dig deeper

yea re the energy balance
previously I super insulated but at the cost of huge time constants, 4+hrs to equilibrium
better to accept and simply quantify the secondary losses

[bobo5195]

Ive seen thermal rigs which instead of insulation used heaters

Ie heatsource - some insultation - heater.

Heater temp is aligned to current heatsource. No temp differential, no heat transfer. Equilbrum should be fast but added complexity

I'll have a look around for stuff. I know some people in my year did a precise thermal test rig for plastics last year but i should have a paper with ideas somewhere or other.

[BillA]

B5
yea, a guard heater
be a bit of a buggar in an environmental chamber - but doable

an interesting matl is cu-co-be UNS C17500 with a thermal conductivity of 180 and a Rockwell B hardness of 100 vs. 37 for cu
- I cannot find a hard brass with any conductivity, and bronze is worse

the combination of thermal conductivity and hardness probably has many answers, as do the material plus machining cost implications

[Cathar]

the combination of thermal conductivity and hardness probably has many answers

Industrial diamond? ;)

[BillA]

"as do the material plus machining cost implications"

mercy, I don't know if I can handle carbide !

[jaydee]

Modified drawing pics attached. Left out sensor holes for no idea where to put them.

Changes?

[bigben2k]

Oh so much to cover (I go away for one day, and so much activity!!!). I'll tackle in varying order.

As for the die material: I have to consider what's commonly available, so I refer to our sponsor:
http://www.onlinemetals.com/index.cfm?affiliate_id=302
(link from Main page)

- Invar (an alloy of 36% nickel and 64% iron)
- Nickel Alloy R405 (similar to Monel)
- Titanium
- Tool steel (including "ALLOY 1018")
- Stainless

Maybe dubious purity, would not care to see 392, 396, 400 debated again.

My concern however is with the maintenance. Was thinking about some type of plating followed by a grind to restore die to same total height. The idea still needs thought, but all in all, copper's softness is a problem.

Damage to the heat die could be avoided/minimized with a proper mounting plate that would have "guides", but without interfering (significantly) with the final alignment. The damage expected would be a rounding of the contact area's edges.


As for dimensions, if we "stretch" (!) the Jedec 85% uniformity requirement to 85% of actual die size, then 12 by 12 mm will not do (extended, 12 by 12 is useless, see below).

I've gathered many actual core dimensions (a hard exercise!) but found most of the info at geek.com . For Intel, excluding the old Willamette core, core sizes vary between 112 mm2 and 237 mm2. That means using two dies, 10 by 10mm and 14 by 14mm, which actually does cover every core, within 15%. I have not collected all data for AMD.

Below is the collected data, complete with source links:

"CPU core dims and power"

Intel:

Smithfield 90nm
206 mm2 / 95 to 130 Watts
from THG

Prescott 2M 90nm
135 mm2 / 84 to 115W
from: http://www.digital-daily.com/cpu/intel-prescott-2m/

Gallatin 130nm
237 mm2 / 54 to 97 W
from: http://www.geek.com/procspec/intel/p7server_13_4.htm

Prescott 90nm
112 mm2
from: http://www.extremetech.com/article2/0,1558,1478683,00.asp
103W
from: http://techreport.com/reviews/2004q1/p4-prescott/index.x?pg=2

Northwood 130nm
131 mm2 / 61 to 68W
from: http://www.geek.com/procspec/intel/northwood.htm

Willamette 180nm
217 mm2
from: http://www.geek.com/procspec/intel/p7consumer.htm
52 to 72W
from: http://www.cpuscorecard.com/cpuprices/ip4.htm

AMD:

Toledo/Manchester 90nm

San Diego 90nm
115 mm2 / 104 W
from: http://www.tomshardware.com/cpu/20050627/athlon_fx57-02.html

Clawhammer 130nm

Venice 90nm

Newcastle 130nm

Winchester 90nm

Sledgehammer 130nm

Clawhammer 130nm

Clawhammer old 130nm

Newcastle 130nm

Paris 130nm

Palermo 90nm

Thoroughbred B 130nm

Thoroughbred A 130nm

Barton 130nm

Thorton 130nm

[BillA]

10x10 and 14x14
ok by me, 14 should serve for GPUs moderately well ?

[bigben2k]

Oumpf. the 15% margin isn't there (after further review).

Let me gather the AMD data first.

[bigben2k]

Some more info:
http://www.tomshardware.com/cpu/20041221/images/cpu_history_big.gif

I'll recompile.

[jaydee]

Some more info:
http://www.tomshardware.com/cpu/20041221/images/cpu_history_big.gif

I'll recompile.
Link dose nothing.

[Les]

Copy and paste works
God, it is a big list

[jaydee]

Copy and paste works
God, it is a big list
Had to close all browsers first then paste and it worked....

Big list indeed. Any idea on tomorrows die sizes?

[bigben2k]

Copy and paste works
God, it is a big list
...and quite the lovely puzzle too:
-Clawhammer on 754 and 939
-Barton on Athlon XP and Sempron
-I may have skipped over the mobile and servers...

I think that this exercise is just going to be about completing the missing elements of the THG chart (below):

(updated as needed)

Toledo/Manchester 90nm
199 mm2 / 110 W

San Diego 90nm
115 mm2 / 104 W

Clawhammer 130nm (socket 939) model 4000+
144 mm2 / 89W
from: http://geek.com/procspec/amd/k8.htm

Clawhammer 130nm (socket 939) model 53 / 55
144 mm2 / 89W

Venice 90nm
84 mm2 / 67 to 89W
http://www.xbitlabs.com/articles/cpu/display/athlon64-venice_3.html
(core size "same as Winchester").

Newcastle 130nm
144 mm2 / 89W

Winchester 90nm
84 mm2 / 67W

Sledgehammer 130nm
193 mm2 / 84.7 W

Clawhammer 130nm (socket 754)
193 mm2 / 89 W

Clawhammer old 130nm (socket 754)
193 mm2 / 89 W

Newcastle 130nm
144 mm2 / 89 W

Paris 130nm
118 mm2 / 89 W

Palermo 90nm
> 84 mm² / 62 W
http://www.presence-pc.com/tests/Athlon-64-Venice-et-Sempron-Palermo-295/3/
(in french, but states "> 84 mm²", closest available estimate. Consistent with various other statements)

Thoroughbred B 130nm Athlon XP model 1700+ to 2800+
84 mm2 / 59.8 to 74.3

Thoroughbred B 130nm Sempron model 2800+ to 3?200+
101 mm2 / 59 W

Thoroughbred A 130nm
80 mm2 / 49.4 to 67.9 W

Barton 130nm Athlon XP 2500+ to 3000+
101 mm2 / 68.3 to 76.8 W

Barton 130nm Sempron 3000+
101 mm2 / 62 W

Thorton 130nm
101 mm2 / 60.3 to 68.3 W
http://forums.amd.com/index.php?showtopic=53302
("Basically, it's a 'Barton' with half of the L2-cache disabled.")

[jaydee]

Also are we going to forget the IHS exists or make a compensation?

[BillA]

the die
JEDEC
IHS is well known, been discussed ad nauseum; go to the lit

[Ice Czar]

but sufficient to understand that our efforts are not in a vacuum

or are as the case may be :p

Thermal Contact Resistance Measurments under Vacuum (http://grs-sei-amd64.stanford.edu/research/archives/report_jan17.pdf) @ U of Waterloo 2003
via Stanford S.T.E.P.

pretty much your first link

Experimental Apparatus & Proceedure
All measurements were performed using the thermal interface material test apparatus at the MHTL shown in figure 1. This apparatus, as described in the publication included in the Appendix of this report uses a pair of calibrated heat flux meters with equally spaced RTD elements to measure the total heat flow rate through the joint. Heating is provided by 4 cartridge heaters in a copper block at the bottom of the test column, a liquid cooled cold plate at the top of the column acts as a heatsink for the system. Loading is perfornmed using a linear actuator connected to a lever system, and a 1000lb load cell is used to measure contact pressure at the joint. The entire measurement apparatus is contained in a vacuum chamber, and all tests are performed under vacuum conditions, p<5Pa (0.037torr). A Keithley 2700 data aquisition system is used to perform all the measurements, and data logging and control of the experiment are performed using Labview v.5.i software running on a Windows-based PC.

Two approaches are traditionally used to stabilize or eliminate heat losses, i) a guarded heater where surrounding conditions are controlled through a secondary heater and ii) a vacuum environment where conduction and convection heat losses are minimized and radiation heat losses can be controlled through a radiation heat shield.

http://images.dr3vil.com/upload2/stanfordtest.jpg

the construction notes in the appendix are quite detailed
and relating to the actual question they used Aluminum 2024 for the flux meters

it looks like because of the tight dimensional control of the flux meters they are able to measure the temperature gradient and with the thermal conductivity of the Al 2024 determine the heat flow rate.
larger size of the flux blocks to get that gradient being the reason I assume they opted for a vacuum over the added complexity of insulation and secondary heaters when employing the RTDs
so provided the same data is available for other alloys and they are truely homogenous...

[bobo5195]

As always with you guys im going to have to go over this I H S stuff but at the moment I’m in a “I couldn’t disagree more mode, I H S good” but I’m sure the argument has been beaten to death.

Here’s a thought though. Why cant you use a die/I.H.S. sim block. Get a block of metal (silicon if your being pedantic) and attach it with thermal paste to you heater assembly. Measure the temp in this block of material and you need not worry about die size of the heater anymore as my swapping around this top piece it can easily be changed. As long as things are well insulated all the heat is going through this core so you’ve maintained Q. You can easily make this little assembly into a nice I H S rig (pre-made and stuff so bolt on and test/ test various versions all pre cured. You could pre cure all the blocks I H S assembly for a week quite easily) as well and if it gets scratched build yourself a new one!

[Incoherent]

Some comments

Assuming a calorimeter type sensor placement, what is the necessity to use copper for the heat die ? (i.e. does the matl's conductivity matter so much ?)
while Ben's suggestion to use iron seems radical, why not use a more durable material ?

I think the only criterion for the material conductivity is that it is known. Steel has many grades and different k's which is why I didn't use it. If I could be sure of it I would have no hesitation using steel. Silicon carbide is another good option, machining aside. We use a variant at work with a very low CTE which has a k of 170, which I have been looking at. Not in my price range though, especially if machining is factored into the equation. If we could set up an accurate tester of thermal conductivity it would be rather useful. Secondary losses in this test are even more critical than the heat die.
There are other more trivial issues. Copper is so far ahead of all other suitable materials in terms of conductivity that I have been a little concerned about how much heat is generated over these long heat paths. Using heater cartridges mitigates this concern somewhat (versus the metal film power resistors I use). A positive aspect of this is that with the higher temperature gradients comes a lower dependence on measurement accuracy. Water temperature measurement resolution and accuracy remains of critical importance if heat to water needs to be measured.

Guard heaters are a direction I like, possibly an easier way around the secondary losses than proper insulation (vacuum).

Sensor holes and position. Depend of course on sensor size. Heat shadowing and other similar effects are problematic as is the fact that the waterblock itself will effect the temperature gradients in the die. One suggestion, one I will act on in future, with centred holes drill all the way though. The temperature cross section will be symmetrical, even though the heat shadowing is worse the compensations are much easier.

BTW Bill, the phenolic arrived, thanks. I will not be able to do anything with it for a while, work and move dominating life right now.

[BillA]

I'll investigate mal\tl costs and fabrication shortly
what are your thoughts on sensor # and placement
I'm looking at 3 to 5 sensors in these calorimeters, why not 3 vs. 2 ?

my last setup at TMT used a guard heater (a flat iron on Low with a Variac put in an insulated box with the heat die inside and level with the top)
with a PID controller it reduced the time constant to an hour or so - 75% reduction from super-insulation alone
- pretty crude though

[BillA]

AlSiC ?? http://www.alsic.com/papers/cpseuro992.pdf

how much interest might there be in this ?
the sintered piece would have a big pedestal which could be cut down as desired

[bobo5195]

Forgive the somewhat newbieness of this post but why on earth does it take so long for loops to water up to a stable condition?

Surely use of guard heaters as extra heaters and pre heating of the water in the loop should make heating of water far less than an hour. It might require you to be ready by the off switch but I see no reason why the loop cannot be prodded in the direction of thermal equilibrium very quickly.

I assuming here that your using a closed loop to test with as opposed to a open and quasi open loop with a large tank of water and the use of a secondary heat exchanger to obtain accurate water temps is not used (heat exchanger used in closed loop to cool water to pre-described level in a short closed loop ie pump with restrictor, heat exchanger and pump. Allows also for secondary measurement of heat input by level of heat addition to well insulated secondary tank)

[Incoherent]

what are your thoughts on sensor # and placement
I'm looking at 3 to 5 sensors in these calorimeters, why not 3 vs. 2 ?


I had three on the previous fluxblock. I found that it the temperature gradient was very linear so dropped the third sensor on the current version. Still, having more would be a good idea, especially if people want to calculate heat flux, the more data points the better. The disadvantage is that if you have inline (drilled into the heatpath) the effects of the sensors on the heatpath become more dominant. Also, a longer heatpath is then required to accomodate them, in a 10x10mm channel this would lead to very high temperatures, increasing secondary losses etc.
As far as placement relative to the interface, I am in two minds. One way is to have them quite far away, like 3mm so that the sensor effect on the surface is minimised, more length to even out the temperature at the actual surface. On the other hand going as close as possible minimises the error of any extrapolation. I think that whatever one does, assumptions need to be made and the problem modelled in order to correct for the heat shadowing. Les and I have been exploring this a bit in the Fluxdie thread.
I of the opinion that the only really safe way to position the sensor is in the centre of the heat path despite these shadowing effects. Of course, this means that the sensor needs to be as small as possible and the die CSA as large as possible to minimise errors. Since we want to test 10x10mm this limits us. Small thermistors are also not very cheap. I was intending to use Betatherm thermistors (0.457 or 1.01 mm diam.) but the cost stopped me, at ~$10 each with my tendency to destroy perfectly good sensors through mishandling this is untenable. I use Mitsubishi, RH16's which are 1.5mm in diameter and under $1.00. RTD's I am not up to speed with. Thermocouples can be any size so are probably a good solution for most people, especially since to get thermistors accurate/linear there is a convoluted calibration procedure.


Re AlSiC. I'd be very interested.

[Incoherent]

...(a flat iron on Low ...)...- pretty crude though


I'm all for crude, if it works.

[BillA]

looky here: http://www.tc.co.uk/news/news_minisensors.htm
info on 4-wire 0.5mm dia RTDs requested

bobo
water chillers, chamber, inst., etc. all good to go in an hour
the problem was with a heat die having 4+" of insulation coming to a steady state condition (reading to hundredths eh ? with a probe in the insulation)

my preference would be for a heat die designed (or adapted) to have a 20% secondary heat path loss, this a nominal mobo/socket (through the traces) sink 'value' described at an IDF by Intel
the actual value is different for every board

[bobo5195]

Ah i see.

Im worried about this secondary heat path as you are no longer exactly sure (for a well laged die) of the power input. Surely it would be easier to just apply an analytical model and say there is 20% less heat input and such. It is far easier to insulate everything well than have a well designed secondary path with debatable characteristics.

Could also try and use emprical relationships using a watercooling loop to measure energy output into it from a cpu versus the actual cpu power. Given that the heat die system can give you everything else.

[BillA]

the insulation is going to be a big deal for the riser w/sensors
best might be to pot the bare element w/leads into a filled cross drilled hole
the phenolic insulation could be cut for one side with RTD lead holes and sealed to that riser face, the remaining to insulate the other 3 sides (and locate ?)

this is what I was asking Stew, if the rad Q is measured via flow and temp - why not also the wb ?

[bobo5195]

Thinking about things i am abit uneasy about this whole concept of hole shadow, especially given that this thign is in equilibrum and well insulated.

[redleader]

10x10 and 14x14
ok by me, 14 should serve for GPUs moderately well ?

I agree.

Prescott was one of the largest CPU cores in recent times (ignoreing dual core), and the ball park for the core is just 70mm^2. The rest is just cache, which doesn't actively produce significant heat, but does dissipate some heat via conduction from the core itself.

100mm^2 should be a fine middle ground between current dual core processors and current single core processors. Future dual cores will likely be closer to 100mm^2 anyway.

I'm not sure about GPUs. I've never seen a layout of their functional units. I'd guess its fairly uniform over the whole die though since there is no cache and many symetrical pipelines.

[bigben2k]

looky here: http://www.tc.co.uk/news/news_minisensors.htm
info on 4-wire 0.5mm dia RTDs requested...
Oh please share any info you obtain!
Pricing:
http://www.tcdirect.co.uk/deptprod.asp?deptid=230/29


Going through the core sizes this morning, narrowed down to 90 nm only, we have:

Smithfield 90nm
206 mm2 / 95 to 130 Watts

Prescott 2M 90nm
135 mm2 / 84 to 115W

Prescott 90nm
112 mm2 / 103W

Toledo/Manchester 90nm
199 mm2 / 110 W

San Diego 90nm
115 mm2 / 104 W

Venice 90nm
84 mm2 / 67 to 89W

Winchester 90nm
84 mm2 / 67W

Palermo 90nm
> 84 mm² / 62 W

This would dictate:
-10x10 to cover:
Prescott (112 mm2), San Diego (115 mm2), Venice (84 mm2), Winchester (84 mm2), and Palermo (84 mm2).

-14x14 to cover:
Smithfield (206 mm2), Toledo/Manchester (199 mm2)

...which unfortunately (?) leaves out Prescott 2M (135 mm2) in an intermediate position (do we care?).

I am happy with 10x10 and 14x14.

[RoboTech]

In regards to concerns about thermal shadowing of sensor holes...

One idea I planned to try in a future die sim was to bore/drill a tiny hole (1/16") up thru the center of the heat die, to within ~1mm of the top die surface. The hole would pass between two cartridge heaters and the bottom opening would allow sensor wires to exit out the bottom. One sensor would be inserted all the way up to the top, blind end. A second senor would then be inserted behind the first one to a desired distance from the first ( say 10 to 20mm). Omega makes some very small RTD's (all flavors: J,K,T, etc) that could be thermal epoxied in place inside the bore.

The top surface area would effectively be a square with a tiny hole in it (although not breaking thru to provide better top temp measurement). Building the die in this way would eliminate any shadow. The top surface area calc would exclude the area of the hole. The hard part will be drilling a very small hole that deep - especially if its in copper!

Edit: Alternatively, two (or three) parallel holes could be used, each for its own sensor if there was concern about spacing, clearance for multiple sensor wires, and possible heat conduction thru wires from one sonsor to another). This could also allow for a tighter fit of the sensor in the hole.

Just a thought...

[Incoherent]

Just a thought...


I like that idea. The thing that would concern me is the uncertainty of the measured temperature location. For what I am doing an important part of the equations is knowing where the sensor is in the heat path.

[BillA]

no, even the centerline assumption for a horizontal wirewound is a bit iffy for what we want
(poor boy all the way here)

hey Ben, you see the price !

[jaydee]

Any more ideas on the design? Will try to draw it up if you give specs. Will then send it to who ever wants it in and what ever format Solidworks 2003 can put out.

[bigben2k]

Yeah, pricey.

I'm perfectly comfortable with a square die, but the upcoming lines of dual-core offerings might throw a wrench.

[BillA]

FWIW, dual cores should have dual independant sources
sorry, that's how its done in the big leagues

and 4 core to come ?

suggested is that the technical sophistication may soon exceed the 'practical' participation of all but big players

jd
you have a go but we lack some of the bits yet, let's list what we need;
1) sensor #
2) sensor placement
3) sensor selection/dimensions
4) sensor hole definition + tolerances
5) heater selection/dimensions
6) heater hole definition and tolerances

5&6 are no biggie, 1-4 need resolution
I'm trying to source some sub-mm RTDs at a tolerable price, give me a bit
- anyone out there use such ?

[bigben2k]

Bill, I haven't even able to find one, until you pointed one out!

The closest item I have is an element (only) from Omega, 1mm diameter, 10 mm long. 2 wires:
http://www.omega.com/ppt/pptsc.asp?ref=1PT100G_RTD_ELEMENTS&Nav=temc13
p/n 1PT100GX1510
$51 ea (in their bare configuration)

You're welcome to what I've found so far:
http://www.newportus.com/Products/RTDprobe/RTDElem.htm
http://www.newportus.com/Products/RTDprobe/1PT100G.htm
http://www.airpaxtsp.com/tspsite/tproduct.html
http://pyromation.com/products/prt.html
http://www.minco.com/support/ts103.php?section=11
http://www.pyrosales.com.au/thermocouples.asp
http://www.riedon.com/rtd.htm

or to try GlobalSpec

or to go through the WBTA weblinks of manufacturers of temperature equipment:
http://wbta.us/index.php?option=com_bookmarks&Itemid=45&mode=0&catid=21&lang=en

[BillA]

someone makes them smaller, suspect Germany as the source for the UK
?