No announcement yet.

Inlet Temperature Profiling…

  • Filter
  • Time
  • Show
Clear All
new posts

  • Inlet Temperature Profiling…

    Hi everyone.
    Well, I had a bit of an "Ah ha!" moment not long ago. While trying to compare notes with a fellow Corretto roaster, we were both both getting frustrated while trying to compare roasting notes based entirely on the standard bean mass recorded temp profile.

    My frustration has always been that a normal profile is really only a recording of what has actually happened to the bean mass, and not what the actual temp 'input' was - so it makes it tricky to repeat, or pass on to someone else for testing! This is extra tricky with different BMs, HGs etc, as my "350deg" gun temp might be different to your "click setting 10."

    Anyway, my "Ah ha!" moment was to do an empty run and slide the DMM probe under the corretto lid, so that this tip was right in the middle of the entry port. This then allowed me to measure the actual temperature entering the pan out of the gun, based on the successful 'ballpark' settings I had been using on my setup to give consistently good results. I was then able to pass these on.

    In theory therefore, no matter which HG/BM combo you use (fixed temp with height adjustment or adjustable temp) you could if you wish play with your height/settings to get identical inlet temps for various points of the roast - allowing very close comparison between profiles. There will still be some variables (lid design/insulation/depth of pan etc) but they should be minimised.

    The findings on actual inlet temps were interesting. Based on my Bosch HG, the inlet temps I have used for my regular successful roast profile were as follows:

    Roast Stage Bean Mass Temp Gun Setting Measure Inlet temp

    Prewarm > 30 deg 200 deg 140 deg

    Step 1 30 > 130 deg 350 deg 250 deg

    Step 2 130 > 160 deg 400 deg 290 deg

    Step 3 (> 2C) 160 > 185 deg 450 deg 330 deg

    Step 4 (Roll 1C) 185 > 210 deg 400 deg 290 deg

    Step 5 (till 2C) 210 > 221 deg 350 deg 250 deg

    This is a basic profile - I'm playing around with the 150-160 mallards zone currently - but this procedure/temp input was the one that got me into the sweet spot. I have seen mentioned that commercial roasters have an inlet and bean mass probe - I imagine for this reason (how else could you log what temp setting a gas jet burner is!).

    My question is - has anyone else played around with inlet temp profiling in their corretto?

    Cheers Matt
    Attached Files
    Last edited by DesigningByCoffee; 5 September 2012, 03:13 PM. Reason: Darn HTML - where's my table gone :-)

  • #2
    Been playing a bit more with this concept this weekend, logging the full range of heatgun settings and recording the inlet temperatures. These Bosch guns are amazing! Basically a 7.5 degree increase inlet temp for every 10 degrees on the gun - almost right through the range!

    Anyway, I've been playing with my profile sheet to incorporate this information in a usable fashion. I've attached a copy of a blank profile sheet as well as a completed sample, based on the preferred profile I'm using at the moment.

    The most useful thing in my books is seeing where in the roast the input temp is being increased & decreased, and by how much, to achieve the final curve. I'd be really interested to see what others are doing the achieve their favourite results on different beans? Maybe I'm just OCD - but this info has transformed my roast thinking :-)

    Happy roasting everyone!
    Attached Files


    • #3
      Impressive stuff Matt...

      Not so OCD by the way. Can never have too much info when roasting if you're trying to accurately profile a particular batch.

      Can't really do this with my setup as I only have one DMM and can't really afford to buy another one. Still, worth doing if you have the resources...



      • #4
        Hi Mal
        That's the great thing! If you've got a DMM already, you can 'profile' your existing HG/Corretto setup, then share the details with others more accurately! This is what excites me about this - we can now remove just about any gun/setup specific jargon, and simply talk about specifics that can be measured precisely using the DMM - the heat going into the roaster (measured and recorded once as a baseline) and then the temp profile of the bean mass - which will vary bean to bean, roast to roast.

        So on Saturday, I just ran through all my digital gun settings (or it could be various tripod heights on a fixed gun temp setup, or click stops on an Ozito gun) with my existing DMM and recorded the results. Took about 10 mins.

        Now that I've recorded the actual inlet temps logged against my heatgun settings (the conversion table on the LHS of the page) I don't need to do it again, as these won't change unless I change heatguns. I still use my normal gun 'technique' for my roasting, and I certainly won't be logging that inlet temp each roast (as this won't change much - and you would need two DMM's). The sample graph I provided is really only to demonstrate my current input temp 'technique' - it wasn't a real-time recording.

        But now if I wish to share my technique with you, I can now pass that on in a fashion that is transferable between corretto setups!

        So rather than saying "roast from 30deg - 130deg (bean mass temp) on gun click stop 6" or "on 10cm above the pan lip" (which is frustratingly gun/setup specific, and only useful to the exact same gun owner/setup user) I can say "from bean mass 30deg - 130deg use an inlet temp of 250deg (which can be achieved in some fashion from any fixed or adjustable gun!).

        I now wish I had thought of this with my fixed gun tripod setup - I could have measured the temp drop for each cm of height gained - would have been interesting to see the results :-)

        So the long and the short of it is - I'd love to know the inlet temps you have used in the past, as a really experienced corretto roaster, to achieve your best results. Now I know how to acheive those temp inputs on my setup - I'd love to try and replicate them :-)

        Cheers Matt


        • #5
          I took my Bosch 630 HG and fitted an Aldi Power meter to it.
          The meter shows the watts etc that an item that is plugged into it is drawing.

          Started to profile my HG and check the watts drawing at the different temps.

          Now I thought that as the heat went up the watts would go up at some similar rate....NOT SO.

          There must be some type of PID as the watts jumped all over the place.
          From as low as 125w to 1512w to 650w 157w etc not as expected....

          If it has a PID in the control system that could explain the "metronome" consistancy of the HG.

          Happy roasting

          (copied from Coretto Cover Project)
          Last edited by sando; 6 November 2012, 12:46 PM. Reason: typo


          • #6
            For those interested - my slightly revised profile sheet & sample roast, still with inlet temp conversion table :-)
            Cheers Matt
            Attached Files


            • #7
              This is a great thread Matt,

              One question. did you find the temperatures settled? I was doing an initial test and found that on my HG "Slide setting 1" for example. THe temp was say 62.. but it didnt stick at 62.. it moved around a bit.. mostly up.

              Do you wait for the temp to settle and then take then write the temp down?

              I see that you didn't bother going all the way through the heat range, i assume it would be pointless testing temp of the hg at say 500, because we wouldn't want it that hot in the BM anyways?

              One of the most interesting things i found with my HG so far is that there is a vast difference between 2 settings on mine. I use the little notches on the adjustment slider and find that i have temp difference of almost a 100 deg sometimes.


              • #8
                Yeah, there was a little settling - but not much. I just waited until it had basically stopped rising…
                The Bosch HG is super accurate…I didn't go through the full range - the BM/pan was starting to overheat, and once I'd done that many settings I knew it was a swiss timepiece! Happy to call it :-)

                Some of the guns are a little hit and miss - but at least you have a ballpark 'inlet temp' to compare ;-)