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. The problem with using the excel files is that they aren't being generated in an appended log fashion. Meaning they don't auto generate on a schedule or append to a file on the fly. They are instead generated when you use the manual export function. But, yeah, they are a piece of cake to parse the latest value from (tail -c15 tenma.xls |sed 's/*//g'). If they just auto generated. Reading up on HID drivers
    Bought the Tenma 77-7712

    Sadly ran into a number of issues.

    1. PC driver only

    2. Excel file is generated by the PC software that accesses the feed

    3. The PC software only outputs the excel when you hit the save button (so you can just slave a pc to the task of reporting the data to a central file server)

    I know this is off topic for Over Clocker, but since this is the most informative review of the 7712 on the net, I just wanted to make these notes. If I manage to crack this nut, I report back (a cracked nut being a method for getting real time data out of the device, in a more actionable form that the compiled app it comes with)

    - Will
    I am attempting to take control of my kiln with a computer, and wondered if you could confirm a couple things, that are alluded to in the article, but I wanted to confirm before I buy the meter.

    1. Does the computer interface continuously update on screen? It seemed like you were saying it does, but I wanted to make sure (pc).

    2. Does the meter operate and write files while the usb connection is active? I can run this through an old PC if I have to, but would ideally like to run it with either a Mac or Linux. If I can access the the usb while it writes, in anything close to real time (several seconds is fine) then I can just :load most recent file, parse data, delete the files, then wait for the next one | or alternatively, load the excel document, parse it, then reload it and reparse. Whichever, but the problem being does it stay active while connected via USB.

    3. The above assume you are downloading the file from something resembling a usb file system, as opposed to a aspect of the PC software, is this the case?

    Really appreciate any info you can provide, and the progress it will give me in my glass casting efforts / home stereo kiln temp announcement system (ala star trek core temp computer voice overs)

    -- Will
    Archer0915
    http://yfrog.com/0ofile13842z

    The video is not great quality but I could not get further away and where it was located I could not focus manually. I saw what I needed to.

    Smoke generally goes over and around or just stops.

    Smoke served the purpose I guess. What I see is a situation where unless you have some pressure behind the air the cooling is almost moot. Oh and this is not a 12 phase system either it is 4+1. Kind of limits a sustained high OC don't ya think?

    This is an AMD system rated for the X6 and 140w. I really believe this type of setup cooling the NB with integrated GFX is a limit to both if the IGFX are used as they will get hot and limit an OC on either. I guess this is how they market the FX. This is a GX board.

    The wife almost killed me. She hates incense. I asked if she would rather I started smoking. Long story short I am on the couch with a knot on my head:(


    Surprised you got the resolution you did pretty good effort, a little more focus and maybe a black background board. These these kinds of ideas are kind of an evolving thing.

    I used a kerosene based insect fogger (outside) once on a 10 inch fan and my wife was none to happy when the wind changed and blew it back through the house open windows.
    http://yfrog.com/0ofile13842z

    The video is not great quality but I could not get further away and where it was located I could not focus manually. I saw what I needed to.

    Smoke generally goes over and around or just stops.

    Smoke served the purpose I guess. What I see is a situation where unless you have some pressure behind the air the cooling is almost moot. Oh and this is not a 12 phase system either it is 4+1. Kind of limits a sustained high OC don't ya think?

    This is an AMD system rated for the X6 and 140w. I really believe this type of setup cooling the NB with integrated GFX is a limit to both if the IGFX are used as they will get hot and limit an OC on either. I guess this is how they market the FX. This is a GX board.

    The wife almost killed me. She hates incense. I asked if she would rather I started smoking. Long story short I am on the couch with a knot on my head:(
    Cough, Cough, Thanks for the idea, cough. This will be a low speed test as I cant see anything but (unless air is being directed there intentional, have not seen it before) limited air movement around the mofs.

    I will post some shots tonight I hope.
    Only way I have made smoke work effectively was to turn fans down to about 1000 rpm and then hit it with a stobelight.

    I have also used a tacky glue on the fan and then used a talcum powder to see where the airflow stalled or was attached to the blades.

    We have used spray paint also on fans only - makes great patterns also, lol...

    Talc is a kind of smoke If you do not mind the mess associated with it - take a video throw a bunch in and then observe frames individually Vacuum it out when you are done. Strobe-light would most likely improve the visual effect and quite handy for this kind of stuff. might want to wear a mask
    Yeah. I am hoping that everything will work. I will be using a lot of incense sticks hoping to generate enough to video. I guess I could soak them in oil too.
    JoeC
    A duct tape grid would work, though would be a little cumbersome.

    I think a Plexiglas sheet is best, something that you could use to test or review any case but this would be great to get your feet wet.

    Another advantage of using some clear sheet is you can make a airflow probe by attaching fine thread or tissue paper to a stick and use it to visualize dead spots and recirculation points.

    Sometimes strange things happen airflow wise, occasionally when I test fans I will reduce flow/pressure but it is not picked up by my meters because the air movement has a kind of memory - that is it has a recirculation momentum in a particular direction and maintains/resists despite other changes made in overall system flow. You see it often in cases due to their irregular flow paths.


    I am doing some testing tomorrow with incense (SMOKE). I want to video the air movement over MB heat sinks (MOSFET and NB (AMD) for this testing). I have been looking at a lot of this modern heat pipe on the MB design crap and I have come to the untested conclusion that these types of setups (Gigabyte in the V6GT review) are really no better than a bare block of metal because of poor fin design.

    The air movement in this area is generally minimal and all that is done is hot spot creation. I am going to test this and try and make a point. If I am wrong nothing is lost but I don't think I am.
    Archer0915
    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.



    A duct tape grid would work, though would be a little cumbersome.

    I think a Plexiglas sheet is best, something that you could use to test or review any case but this would be great to get your feet wet.

    Another advantage of using some clear sheet is you can make a airflow probe by attaching fine thread or tissue paper to a stick and use it to visualize dead spots and recirculation points.

    Sometimes strange things happen airflow wise, occasionally when I test fans I will reduce flow/pressure but it is not picked up by my meters because the air movement has a kind of memory - that is it has a recirculation momentum in a particular direction and maintains/resists despite other changes made in overall system flow. You see it often in cases due to their irregular flow paths.
    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.

    Another thing you can do for case cooling, something we use on consulting projects.

    Remove the side panel and replace it with a plastic panel that has small holes drilled one inch apart in a grid pattern across the whole sheet.

    Attach the thermocouple to a round stick (I use wooden shishkabob skewers) and mark the length in one inch increments.

    Start at a point on the grid and measure 1 inch depth, 2 inch, 3inch etc. till you reach other side, now move to the next grid point.

    This will give you a full 3 dimensional thermal profile of the case helping to troubleshoot and identify hot spots, dead air or recirculating air.

    Cover unused holes with tape

    There are air probes you can use also but if its hot thermally chances are you have located a low air flow point anyway, the exact number is not that important 99% of the time.

    Good stuff


    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

    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.
    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. ;))
    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.
    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. :-)
    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