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HeatSnob - Grounding errors with non-supplied probes

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  • HeatSnob - Grounding errors with non-supplied probes

    Just received my Heatsnob and it works fine with the supplied short probe but will not work in my roaster with either of the long probes that were purchased from beanbay (yellow cable or meal braid).

    I get this error in Roastmonitor: "19:03:04 meter 1: Thermocouple shorted to ground "

    There seems to be a compatibility issue with the type of thermocouple used with it, the new probe is isolated from the probe case and the others are not and in my roaster the case of the probe is tied to ground. I suppose that is one advantage of the old meter being optically isolated from the PC.



    Gary

  • #2
    I'm glad the supplied one works!

    Optic makes sense be sheeze, it gave us a lot of grief too... one bit of chaff and people screamed. ;-)

    As for the old ones, I don't know, they should work though.
    One of the gotcha's with thermocouples is that the transpose the red/black sometimes. As some specifications show red as earth!

    Try swapping the polarity and see what happens

    Comment


    • #3
      From Roastmonitor, with the polarity swapped it counts down for an increase in temperature and when the probe case is connected to ground it stops counting and I get same error.

      Looking at the output of HIDTester2 I can see the "short to ground" data change.

      The short probe supplied is fully isolated, are you likely to get more stock of long probes in Beanbay (that work) or do I look elswhere ??


      Gary

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      • #4
        The long probe I bought from bean bay works with my heatsnob.

        Comment


        • #5
          The long probe I bought from bean bay works
          Can you check if it the thermocouple is isolated from the probe case or is connected to it ??

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          • #6
            Originally posted by gazza View Post
            Can you check if it the thermocouple is isolated from the probe case or is connected to it ??
            I'm away for a week or so but can check when I get home if you're still having troubles.

            Comment


            • #7
              Hi Gazza

              I had a grounded thermocouple (not a beanbay one) and it drove me crazy. It would work fine but once connected to the laptop it would create a ground loop and all the readings would fail. Eventually I had an ungrounded MIMS one fabricated (mineral insulated metal sheath) and it works now.

              If you want to persist with your ground thermocouple easiest solution should be operating the laptop on battery power. Without a power plug there is no ground loop. If you're using a desktop then you'll need to electrically isolate the probe from the entire roaster. Some silicon has a 240C continuous rating so that might be an option. I'm using normal rubber grommets in the outer left wall but if you could find silicon grommets or tubing for the inner wall that might be another option.

              But first you might want to check what temp you need to withstand. Where Andy recommends to install the short heatsnob probe, I get 150C max but you may get different temps depending on your roast profile.

              Anyway, that was my experience. Hope that helps.

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              • #8
                A short length of PTFE Tubing would be better to use than silicone tubing for that purpose.
                Lots available from Ozzie suppliers on the Bay...

                Mal.

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                • #9
                  My HeatSnob seems to be giving much more noise in the readings, the general trend line is right but the RoR is now unreliable as after first crack it's jumping around all over the place between -2 and+12, the resulting curve still looks like a +5deg RoR but the numbers don't read that way. What's strange is that up until about 150deg it reads just like the old meter. I can't test the supplied probe in situ as it's too short. My current probe (a fairly recent purchase) appears identical to the new shorter one and is, I believe, isolated from the roaster itself... It's held in place by PTFE plumber tape wrapped dozens of times around the shaft of the probe (poor mans PTFE tubing). I'm using a laptop constantly plugged in (battery is dead).

                  Any ideas or help would be appreciated.

                  Comment


                  • #10
                    Scratch that, it was a grounding issue. The braided cable was held by a paper clip, to top it getting in the way...which was attached to the roaster.
                    You can see the noise in the RoR kick in at the 3min mark and the spike in RoR is where I took the paper clip off. The grounding issue also appears to be robbing me of a few degrees too.
                    Problem solved, user error.
                    Attached Files

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                    • #11
                      Originally posted by johnandcass View Post
                      I'm away for a week or so but can check when I get home if you're still having troubles.
                      I spoke too soon. I've started running into grounding errors with my heatsnob too. It started after I took the long probe out of the corretto and used it with the victor multimeter for testing meat temperature.
                      Anyway, after reading prloring's post I've resolved it. The probe was held in place through the open top of the bread pan by metal visegrips. It never used to short to ground but now does and the body of the visegrips touch the metal casing of the bread machine. Weird. I can't insert the probe from the side or bottom as the pan needs to twist to lock into place.
                      Anyway, I can come up with another option to hold it or insulate it so easy to resolve.
                      BTW, the grounding issue doesn't seem to occur with the victor.
                      Thanks for the pointers.
                      John

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                      • #12
                        Originally posted by johnandcass View Post
                        BTW, the grounding issue doesn't seem to occur with the victor.
                        Thanks for the pointers.
                        John
                        Probably cause the victor is running on batteries and your laptop is on 240v. Use a multimeter to check the resistance between the probe sheath and the positive and negative terminals. There should be no continuity.

                        Comment


                        • #13
                          The Victor uses an optical connection to the USB cable via an all plastic connector. Hence there can be no continuity between the thermocouple and the computer when using it. Hence, no grounding issue.


                          Java "Well grounded" phile
                          Toys! I must have new toys!!!

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                          • #14
                            Just received the Heatsnob....
                            It installed 1st time.

                            A question on the two probe system..

                            Is there a way to have the Heatsnob default to the 2nd Probe and not the 1st Probe every time ?

                            Plan to use it on the exhaust side where there is a plastic pipe (and the short probe works perfectly there).

                            Main Probe (long 1) is still the Victor Data Logger with Optic connection.

                            Hope its possible...

                            Cheers and thanks

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                            • #15
                              Hey Sando - welcome back! Glad to see you're still roasting

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