Discrepancy in therm readings.

Discussion in 'Meat Thermometers' started by tagalong, Nov 5, 2014.

  1. tagalong

    tagalong Fire Starter

    I have an Ivation dual probe that is same as a Maverick 732 and also have a ThermaPen. I have boil tested and ice bath tested both probes of the Ivation and the ThermaPen and all are within 2 degrees of each other. That being said, whenever I do a cook my Ivation meat probe says that I have reached my desired IT but when I check with the ThermaPen it has been lower by as much as 30 degrees. Can anyone offer an explanation?
     
  2. venture

    venture Smoking Guru OTBS Member

    It is normal to get a little different reading.

    But 30 degrees seems to be off the chart for me?

    Maybe someone else will weigh in?

    Good luck and good smoking.
     
  3. Most probes are thermistor instead of thermocouple.  Thermistor probes have a resistance which climbs as temperature climbs.  If there is a bad electrical joint in a thermistor probe, it can cause a higher resistance reading which may only show up when the joint gets hot (this causes a higher than actual temperature reading).  Do a boil test, while the probe is hot (toss it in a 250 degree oven for half an hour immediately before a boil test).  If it reads wrong, you have a bad electrical connection in the probe.  Unless you are exceptionally handy, discard and replace the probe. I have 2 maverick probes which have failed in that fashion.  Thankfully, I always have some spares around.
     
    Last edited: Nov 6, 2014
    noboundaries and themule69 like this.
  4. Great info. Thanks for sharing.

    [​IMG]

    Happy smoken.

    David
     
  5. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member


    Do you insert the probe, read, then remove... or is in the meat over the length of the cook....
     
  6. tagalong

    tagalong Fire Starter

    Update...

    When I posted this last night I was into a cook and shooting for an IT of 165. About 15 minutes after posting, the probe showed that I was losing IT even though my pit temp was staying steady at 228. It ended up dropping a total of 15 degrees before it levelled and started to climb again. After it had finally climbed back up to 165, I checked with the ThermaPen again and it had gained some ground but still showing about 12 degrees off. Shortly after that the probe started dropping again. It dropped all the way back to 151 then levelled and started climbing back. When it reached 165 this time, the ThermaPen was within 2 degrees.

    Probe is Inserted into the meat about an hour into the cook and left in for the duration.
     
  7. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member




    The shaft of the probe WILL conduct heat down to the sensor... Therefore, with the smoker at 200+, the sensor will read high.....

    The drop in temperature is called the stall.... some have figured this lowering of the temp to "evapotranspiration".... Where the moisture in the meat starts to evaporate and cools the meat... just like you cool off when you sweat...
    It can be overcome with a "foil wrap", or higher smoker temps to bust through that stage (some suggest), or I run my smoker at 200-210, below the boiling point of water...
     
  8. I am thinking you need a new probe.

    Happy smoken.

    David
     
  9. bearcarver

    bearcarver Smoking Guru OTBS Member

    Hmmm, Never had it happen to me, but what Addertooth says makes a lot of sense to me!!

    Could be "New Probe" Time!!

    Bear
     
    Last edited: Nov 6, 2014
  10. noboundaries

    noboundaries Smoking Guru OTBS Member SMF Premier Member

    I've had two Maverick probes fail, one chamber and one food. Thanks to Addertooh now I know why!
     
  11. jaez

    jaez Fire Starter

    I see that I'm not the only one with Maverick Probe problems.  I was smoking a pork loin over the weekend and turned on my 732 with the bbq sensor in the kitchen.  The probe wad reading 144 degrees and slowly decreasing by a couple degrees per read time.  I thought something must be malfunctioning and just happen to have a brand new 733 still in a box that was delivered a few days ago.. Decided to put them out in the bbq side by side and see what the temps read.  The older 732 said that the temp was at 240-250 and the 733 was reading 280-290.  The clips were touching and the probe tips were about an inch apart so there couldn't be that much of a temp change inside the bbq.  

    I decided to trust the 733 and the next day tried the ice water test (boiling water is too difficult with the steam condensing on the wires).  The ice water test gave me a 37-38 degree reading on the 732, which I took to mean that the probe was reading high.  If it's high at the ice water test it should be high at the hotter temps... logically, yet it was the low one out of the two on the bbq... weird.  The 733 probe read LLL when I put it in the water.  I'm going to have to do some digging to find out what the lowest temp is on the 733 and maybe order a new 732 probe..
     

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