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Thread: First DMM Corretto roast - temp and probe questions

  1. #1
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    First DMM Corretto roast - temp and probe questions

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I did my first roast in my corretto setup today (well, third roast, but first with the DMM from the BeanBay). I did 600g of PNG Wahgi AA.

    Got to first crack in about 13.5 min. Rolling first crack not much after that. Im not sure if I got to second crack or not, I suspect I just hit it before I stopped. I stopped the roast when the colour was looking about right and there was a bit of smoke from a few burnt beans (not too many, I just picked out the blackish ones).

    But, first crack was at about 178 degrees and I stopped at 201.3 degrees.

    So, this seems to indicate that my probe is about 20 degrees off. Ive attached some photos of the probe placement and the roast. Its quite close to the bottom of the pan (10mm off the bottom?) and sticks in about 15-17mm. So its well covered by beans, but perhaps too close to the bottom of the pan?

    Any advice?

    Simon.








  2. #2
    CoffeeSnobs Owner Andy's Avatar
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    Re: First DMM Corretto roast - temp and probe questions

    Quote Originally Posted by 080913090D0F0E600 link=1327725726/0#0 date=1327725726
    So, this seems to indicate that my probe is about 20 degrees off.
    ....
    Any advice?
    Good looking roast, Im sure it will taste great too (remember thats the real purpose of roasting!)

    The low reading could be that the meter itself is too hot as the temp at the probe is subtracted from the temp at the meter or it could be because your probe is a tight fit in the pan... thus making the pan act as a heat sink to the probe.

    Dont get hung-up on the number on the meter, the number you are seeing is perfecty correct for your setup and now you can build a library of data based on YOUR setup.

    8-)

  3. #3
    Senior Member artman's Avatar
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    Re: First DMM Corretto roast - temp and probe questions

    They look yummy!!

    I recently posted a question along the same theme, and got some great info in the replies.

    http://coffeesnobs.com.au/YaBB.pl?num=1318770716

    Cheers

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    Re: First DMM Corretto roast - temp and probe questions

    Quote Originally Posted by 6F404A572E0 link=1327725726/1#1 date=1327729130
    The low reading could be that the meter itself is too hot as the temp at the probe is subtracted from the temp at the meter
    Thanks Andy. I had set up on a table when it was cloudy and then just before I started to roast the sun came out and so the Multimeter was in full sun and probably got a bit warm. I think that would easily explain 20 degrees.

    Quote Originally Posted by 4F5C5A434F402E0 link=1327725726/2#2 date=1327734004
    I recently posted a question along the same theme, and got some great info in the replies.
    Artman, yes, I found your thread which was very helpful (not getting too hung up on particular profiles etc). I was just a little worried that the temp I was recording was so low. But, as above, Im pretty sure that it was the fact I left the meter in the sun.

    Thanks! Im looking forward to the next roast.

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    Re: First DMM Corretto roast - temp and probe questions

    I forgot to add a big thanks to Andy for such great customer service in the BeanBay and for providing the RoastMonitor software. It was so easy to be able to look at the temp rise per minute and adjust the heat gun height based on the feedback. Great tool.

  6. #6
    Senior Member artman's Avatar
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    Re: First DMM Corretto roast - temp and probe questions

    I didnt realise the temp of the meter effects the reading of the temp of the probe.

    Just like Andy said, the actual accuracy of the figures is not as important as repeatability. So your 200 degrees might be 210 on my set up, but it doesnt matter as long as they are consistent between roasts.

    Agree, the meter and software makes it so much easier to keep consistency between roasts and monitor things. And it also looks impressive when non coffee snobs see it, makes the whole setup look very scientific!!

    Cheers

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    CoffeeSnobs Owner Andy's Avatar
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    Re: First DMM Corretto roast - temp and probe questions

    Behmor Coffee Roaster
    Quote Originally Posted by 2B383E272B244A0 link=1327725726/5#5 date=1327749179
    I didnt realise the temp of the meter effects the reading of the temp of the probe
    If you dont plug the stainless probe into the meter it will still show you the ambient temperature.... thats the internal thermistor doing that.

    Sitting the meter in the sun or too close to your roaster is great way to make ambient higher than it should be and then the readings on the probe will be lower than actual.

    As mentioned, it wont matter if they are always the same variables but something like the meter sitting in a sunny window mid summer is likely to be hard to replicate every roast!

    So best advice is to keep the meter as close to room temperature as you can, keep the probe touching only beans (if you can) and then the readings will be close to actual.

    Quote Originally Posted by 222339232725244A0 link=1327725726/4#4 date=1327746320
    big thanks to Andy for such great customer service
    Cheers.
    It is a great tool and I cannot imagine doing my commercial roasting without the software now. It shows me where Im at and where Im heading... leaving plenty of time to adjust as needed during the ramp.

    Enjoy!
    8-)



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