Testing Heatsink Temperatures with the Tenma 72-7712 Data-Logging Dual Thermocouple

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The 72-7712 Digital Thermometer from Tenma Test Equipment is a dual thermocouple meter with internal logging capability, USB output for saving logged data, and software up-link.  This unit can become an integral part of a PC testing arsenal by allowing for isolation of case hot spots, heat sink testing, and liquid nitrogen/dry ice work. The limitations start to change and the performance bar can be raised when you know where it is hot and where it is not.

Features and Specifications

  • Compatible with K-, J-, T- and E- thermocouples (others should work, but these are the recommended types)
  • User programmable offsets
  • Internal memory stores 100 sets of temperature readings that can be transferred to PC software
  • Data logging software for real time testing (good for working with fan and component placement and viewing their effects in real time)
  • Ability to export data sets from software in .xls format to do comparative studies and graphing

The graph capabilities of the 72-7712 software are not phenomenal, it does however serve the intended purpose. Though dual software readout (T1 & T2) would be preferred; the logging capacity and decent feature set, as well as an Excel export feature make up for the software weaknesses.

Thermocouple T1 reading

By pressing the T1, T2, T1-T2 button on the meter your view will also change on the software output screen.

Thermocouple 2

Thermocouple T2 reading

Pressing again will display the variance on the software output screen.

T1-T2 reading

T1-T2 reading

XLS output is a useful feature.

Example of exported data to .xls format

Example of exported data to .xls format

Thermal Conductivity

The thermal conductivity of the heatsink material is an important factor in air cooling. Copper and aluminum are the most widely used materials in PC HSF (heat sink & fan) construction. The thermal properties of these two materials are critical to proper cooling of the processor. The chart below shows the thermal conductivity of materials for comparison. The only three that matter for this testing are aluminum, copper, and air (water and the other items may be of interest to those who like to get a little wet).

Thermal Conductivity (k) / WmK
Material at 0°C at 25°C at 125°C at 225°C
Air 0.02
Alcohol 0.17
Aluminium 250 255 250
Aluminium Oxide 30
Brass 109
Copper 401 400 398
Ice 2.18
Molybdenum 138
Pyrex Glass 1.01
Water (liquid) 0.58
Water (vapour) 0.02

Note: Fourier’s Law expresses conductive heat transfer as q = k.A.dT / s where q = heat transferred per unit time (W/h), A = heat transfer area (m2), k = thermal conductivity of the material (W/m.K), dT = temperature difference across the material (K) and s = material thickness (m).


Testing the Efficiency

Methodology: Air can only dissipate a fixed load of heat due to its low thermal conductivity. Having a material of higher thermal conductivity does not always mean better temperatures, but it does allow a potential for lower temperatures, depending on other contributing factors. Testing the two most common heat sink materials to see these differences helps gain an understanding of what the conductivity numbers really mean.

Heatsinks were tested in the same environment to eliminate most other variables

Copper: 56.8 seconds to reach maximum efficiency with a variance of 3.9 degrees centigrade

Aluminum: 59.8 seconds to reach maximum efficiency with a variance of 7.9 degrees centigrade

This is the point where temperatures stabilize (temperature increases are such that after a pre-determined amount of time, ~20 seconds in this case, there is no change)  and heat is dispersed through natural convection. Although this was not the most rigorous and scientific test (not all variables were controlled) this test does show that copper will transfer heat faster and more evenly. A two minute test of both materials (copper and aluminum) showed a 3.7 degree centigrade variance, copper being hotter (this is good, it means it will draw that much more heat to be dissipated). It must be taken into consideration that these heat sinks did not have a fan and the variance may have been different during operation.

Testing Your Heat Sink and Fan Assembly

Using an Arctic Cooling AF64 PRO

Thermocouple 1 location; close to the base.

Thermocouple 1 inserted close to the HSF base.

Thermocouple 2 inserted at point furthest from HSF base

Thermocouple 2 inserted at point furthest from HSF base.

Temperatures

Temperatures

Variance

Temperature above ambient

If the HSF is not equalizing temperatures within a reasonable variance or running 10+ degrees above ambient case temperature (check the temperature at the intake area of the HSF to eliminate the possibility of a hot spot causing the problem), then a re-seat of the HSF may be needed and possibly a replacement HSF of higher quality may be in order.

Comparative Heatsink Testing

The setup: thermocouples were inserted in aluminum transfer blocks alloy for accurate temperature measurement without the risk of potential damage to other costly components.

Temps after ~5 min. This is a level playing field.

Temps after ~5 min. This is a level playing field.

Max temps ~5 minutes with no fan

Temperatures at approx. 5 minutes

This shows the HSFs ability to pull off heat, notice that the stock HSF just can’t compete. Powering up the fans shows how well each can dissipate heat:

Video-Dissipation after fan power up

What Else Can You Do?

One simple idea for improving the PC enthusiast experience is to check the case for hot-spots. Keeping your entire case as close to ambient as possible is probably the most important thing that can be done to keep the HSF operating at its maximum efficiency. A heatsink can not lower temperatures below case ambient and will usually level out 4 to 12°C above case ambient no matter how much money is spent on it. By identifying hot spots, proper fan placement can be made. Although these areas may not seem relevant to CPU cooling, they are. Air circulating throughout the case creates eddies (a current of air running contrary to the main current; a special case is a circular current, whirlpool) which remain hot and by cross circulation make  air around them heat up. Working in a similar fashion to the eddy, dead zones (hot area where there is no mechanical air circulation) may seem harmless, but it is critical to circulate or eliminate this air to alleviate convection (heat transfer in a gas by the circulation of currents from one region to another). For dead zones, a fan may not be an option and directed air may be needed. If directed air is not possible, then closing in/sectioning off this area may be the only option.

Knowing where the hot areas of the case are located allows for fixes that otherwise would not be possible. Gathering information with a good temperature meter will help guide the process of lowering case temperatures and in turn allow for a cooler processor, memory, and hard disk drive.

Thermocouple test probes useful for PC applications:

Air/Gas Temperature Sensor Type K Thermocouple Probe

Immersion Temperature Sensor Type K Thermocouple Probe

Immersion Temperature Sensor Type K Thermocouple Probe

Surface Temperature Sensor Type K Thermocouple Probe

Surface Temperature Sensor Type K Thermocouple Probe

Shots of the 72-7712

All display elements

All display elements

Temperature readout

Temperature readout

Variance readout

Variance readout

Offset adjustment

Offset adjustment

Front view of meter

Front view of meter

Conclusion

Using a dual probe temperature meter with capabilities comparable to the 72-7712 is a definite step up from the volt meter type single probe units that were used in the past. With the data logging capabilities and other features available with this unit, it is much easier to maximize case cooling and potentially gain a few hundred MHz from a heat limited overclock.

With acceptable quality, useful software and adequate features the 72-7712 makes an excellent addition to the tool box of the overclocker, enthusiast or small PC mod shop.

Archer0915

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Discussion
  1. Very nice equipment, great article, I like to see the upgrade. It is nice to have secondary data points to get a whole picture.
    I like the "T" Type for sink and grease testing as it is smaller and less intrusive for holes drilled in sinks or grooves cut into the IHS.
    Ambient at the fan to Intel spec will help nail the temps to an even finer resolution.
    I will have a review of the Cooler Master V6GT up in a few days that has a little more content on the pan test as well as a link to an article specifically on the test.
    We need multipage ability, these things can get long.
    Very nice.
    Out of curiosity, is the data format truly in xls format, or is it a simple tab-delimited text file (or comma-separated, etc.) with the extension changed to .xls to force an association with MS Excel? I've seen that in lots of technical software: just rename it to .txt, and it pops open just fine in any old text editor.
    If it is truly writing in the binary .xls format (with all the extra formatting for the file header structure, etc.), then that's too bad. There's no need to tie to a relatively complex proprietary format when it really is just text data at the end of the day.
    macklin01
    Very nice.
    Out of curiosity, is the data format truly in xls format, or is it a simple tab-delimited text file (or comma-separated, etc.) with the extension changed to .xls to force an association with MS Excel? I've seen that in lots of technical software: just rename it to .txt, and it pops open just fine in any old text editor.
    If it is truly writing in the binary .xls format (with all the extra formatting for the file header structure, etc.), then that's too bad. There's no need to tie to a relatively complex proprietary format when it really is just text data at the end of the day.

    I will have to check.
    @David:
    Thanks for the link. It's nice to see the new equipment at work.
    One thing I noticed: the link reference here:
    Using a pan and riser made for testing heat sinks on a conventional heat source (described in more detail here: Testing)

    is either very slow or dead.
    It would be good to link to the OC forums article here. Sort of like the "methods" paper that we'd always refer to in our later journal articles. :-)
    macklin01
    @David:
    Thanks for the link. It's nice to see the new equipment at work.
    One thing I noticed: the link reference here:
    is either very slow or dead.
    It would be good to link to the OC forums article here. Sort of like the "methods" paper that we'd always refer to in our later journal articles. :-)

    I had problems with the site earlier but it seems fine now.
    @macklin01
    Link post 13
    Here is a file exported from the meter to the included software and then xls.
    It does not open as text in wordpad It will open though
    Very odd.
    It's definitely binary. But I see "JFIF" in the first several bytes, so it appears to be written in the JPEG file exchange format. I guess that makes it pseudo-open.
    In fact, I get the following error in some software (numbers on OSX):
    Import Warning - This is a tab delimited document, not a valid Excel document. The data might look different.

    I'm glad it opens fine in Excel in Windows, so it appears to have a JFIF handler. It looks like our guess was partly right, in that it was renamed .xls to force an association with Excel. But it does not appear to be an actual bona fide excel file. At least not this file.
    Alas, Open Office does not appear to open the file successfully, so it looks like you're locked in to MS to read data from this tool. Interestingly enough, it doesn't read properly in Excel 2008 on OSX for me, either. Stranger still, OSX Preview handles it fine. (via quick view, but not via direct opening.) This makes it look like you're locked into MS Excel on Windows if you want to read the data from your tool.
    Lastly, on a hunch I renamed it to Temma7.jfif. It opened right up in OpenOffice, but as an image and not as text. I couldn't copy / paste any cell elements. Is this how it opens in Excel for you as well? As an image "screenshot" of the rows / columns?
    macklin01
    Very odd.
    It's definitely binary. But I see "JFIF" in the first several bytes, so it appears to be written in the JPEG file exchange format. I guess that makes it pseudo-open.
    In fact, I get the following error in some software (numbers on OSX):
    I'm glad it opens fine in Excel in Windows, so it appears to have a JFIF handler. It looks like our guess was partly right, in that it was renamed .xls to force an association with Excel. But it does not appear to be an actual bona fide excel file. At least not this file.
    Alas, Open Office does not appear to open the file successfully, so it looks like you're locked in to MS to read data from this tool. Interestingly enough, it doesn't read properly in Excel 2008 on OSX for me, either. Stranger still, OSX Preview handles it fine. (via quick view, but not via direct opening.) This makes it look like you're locked into MS Excel on Windows if you want to read the data from your tool.
    Lastly, on a hunch I renamed it to Temma7.jfif. It opened right up in OpenOffice, but as an image and not as text. I couldn't copy / paste any cell elements. Is this how it opens in Excel for you as well? As an image "screenshot" of the rows / columns?

    Actually I use OO. I just don't understand that.
    Try this I think I caused the issue last time.
    Did it open as an image or as an array of text data for you as well?
    If it's just exporting as an image, then it's pretty damned useless as a data format. (Since you'd want to be able to graph and compare data, do fitting and other analyses, etc.)
    macklin01
    Did it open as an image or as an array of text data for you as well?
    If it's just exporting as an image, then it's pretty damned useless as a data format. (Since you'd want to be able to graph and compare data, do fitting and other analyses, etc.)

    What I had apparently done was when I opened it in wordpad, I did a save as and got the first file. When I opened the first one I also got a image.
    I checked this one and it is fine.
    EDIT: this is what I get now
    Bingo!
    Temma6.xls is a tab-delimited, ordinary text file. There is no reason it has to be named .xls except to force file association with Excel / OpenOffice.
    I managed it with nano / emacs / vi at a command line here. :-)
    Thanks for indulging my curiosity.
    It's a little peeve of mine when things are renamed into the wrong file type to force certain programs to handle them. It's not an xls file. :-)
    I honestly never pay it any mind:( there again I also have my areas of anal feelings. Like product reviews that only run benchmarks. Hell anyone can do that. I prefer some content and someone telling my the what and why of the product. A little research goes a long way with me.
    Too true. And nicely done on your multimeter writeup, by the way.
    Regarding the file format, I guess I'm just a fan of calling something what it is. If it's a text file, then call it a text file. I can only imagine the frustration of wanting to analyse the data and installing OpenOffice or Excel solely to open the file, when it turns out to just be text anyway. And in general, I just view it as sloppy standards-breaking behaviour. ;)
    (It's also an insult to those who actually bother to properly code their applications to write true XLS-formatted files. ;))
    macklin01
    (It's also an insult to those who actually bother to properly code their applications to write true XLS-formatted files. ;))

    Now that I agree with:( Sadly I have only ever written stuff to output to text. There again I don't do it for anyone but me.
    JoeC
    Very nice equipment, great article, I like to see the upgrade. It is nice to have secondary data points to get a whole picture.
    I like the "T" Type for sink and grease testing as it is smaller and less intrusive for holes drilled in sinks or grooves cut into the IHS.
    Ambient at the fan to Intel spec will help nail the temps to an even finer resolution.

    Joe it just hit me and for some reason I really don't know why (Busy with family) I did not even consider that you post is actually how I have 2 of my units set up. I use 50% Perf where most put a window, black window unit filter and probe my HVAC thermocouple through to identify fan locations.
    I leave the filters on though as to move them can screw up the entire dynamic. I know in you case you tape the holes which also keeps everything in check but I have found that doing things this way affords the luxury of a case that is almost at ambient.
    http://www.overclockers.com/forums/showthread.php?t=611748&highlight=wicked