MES 40 internal Temps.

Discussion in 'Electric Smokers' started by coop9790, Aug 24, 2013.

  1. I got my Maverick ready check digital thermometer today. I am checking the internal temps of my electric smoker. I have found that the top rack gets way hotter than the bottom rack. Almost 30 degrees warmer. When I set it to 250. The top rack gets to 250 and the display on the smoker says 208. I moved the probe to the bottom rack and it is only off 14 degrees. Is anybody else seeing this drastic of a difference?
  2. geerock

    geerock Master of the Pit SMF Premier Member

    Welcome to the world of mes quality controller........ gen 2 version. Be thankful it works at all.
  3. sigmo

    sigmo Smoking Fanatic

    Don't be surprised when you get very different readings when you move a probe to different places in an oven, incubator, smoker, etc.

    People have it in their minds that an oven or the like will have fairly consistent temperatures throughout the whole box, but my experience with laboratory incuabators and ovens has been that even multi-thousand-dollar "lab grade" units show shocking variations in temperature depending on where you have the probe.

    Further, the temperature will vary wildly as the heating element cycles on and off, so unless you can outfit the box with an array of probes so that you can read them all simultaneously, you can't really know what's happening because the variations even in one location can be shocking.

    I put a data acquisition system into one lab with thermocouples installed in several ovens that sat next to each other.  When the lab QC guy saw that the readings were not really what we wanted, he questioned the accuracy of the thermocouples or the data acquisition system.  So he put all four of the TCs into one oven to compare them.  He saw that they didn't read the same at all, being ten degrees or more apart.  He had them all poking in through the same opening into the oven, and they were 12" long probes.

    When I came up to do a routine calibration for the lab, I took all four TCs, placed their tips together, and wrapped them with copper wire to hold them in close contact right at the tips.  I then put that assembly into a receptacle in a COD reactor (an aluminum block heater with holes for test tubes to fit) pushing the probes down into the block so the tips were at the bottom of the test tube hole.  I stuffed the opening of the hole with paper towel to seal it and hold the probes in place.  Then I fired up the reactor, and let it run up to its setpoint of 150 degrees C.

    All four thermocouples read exactly the same, or at most about 0.12 degrees different at any given moment. I left them in the reactor for a few hours and they drew four amazingly perfect lines, all together, on the data system's "chart". I showed that to the QC guy and then showed him how having the probes even a few inches apart in these ovens showed great variations in temperature.

    That taught us that the temperatures in these ovens varied quite a bit from place to place, even within a few inches.  It all depends on the air currents caused by convection, etc.  With a stirring fan, you can get things to be more consistent.  But even then, in actively stirred incubators, there are variations.

    We were required to have separate sensors on every shelf of certain incubators used for bacteria growth/testing.  Even in a very small incubator, with fan stirring, the probes do NOT read the same.  And this is after calibrating each probe to be dead on, within 1/100th of a degree!

    So in our smokers or ovens, you can expect to find great variations in temperature from place to place and from minute to minute depending on whether the heating element is on or off.

    And if you put some meat in there, then that throws things off differently.  Sometimes, having meat in the smoker actually makes things better.  It tends to even things out.  An empty smoker may be the worst possible case, actually!  The heat capacity of the meat as well as the water evaporating from its surfaces "loads" the oven chamber and causes interesting differences from how the empty smoker behaves.

    Fortunately, it usually isn't that critical anyhow.  Not that we shouldn't shoot for perfection, but it's just that ovens have worked pretty well for many years.  And only recently have we had inexpensive remote-probe thermometers available to show us all how terrible our ovens actually are/were.  [​IMG]

    I put a stirring fan in my wife's oven a number of years back because she bakes amazing wedding and party cakes.  It's the stirring fan from an old gas chromatograph, set up to withstand such temperatures.  It certainly helps make things far more uniform than it was.  But I'd like to build her an oven from scratch.  Looking at even very expensive ovens, I'm usually not very happy with how they're designed and built.  But again, they're generally "good enough for the job", and it's probably not all that critical, really.

    The other thing you run into with these smokers is the way the controllers and the temperature sensors work.

    I found that the sensor/controller in my 1st generation MES40 reads dead on at room temperature, but then diverges from the true temperature as the temp goes up so that by the time you're at 250, the controller/display is off by something like 22 degrees.

    That's measuring the actual temperature of the tip of the temp controller's probe itself. Measuring the air temperature in the smoker is something of an exercise in futility for the reasons stated before. I just wanted to know if the controller was really truly even reporting/reading the temperature of the probe itself.  It doesn't on mine.

    I've speculated about whether Masterbuilt does this on purpose to correct for the difference in the air temperature where the probe actually is versus what they've measured elsewhere in the cabinet, OR if it's just sloppy design and QC.  Beats me, but at least I know what I have to do to correct the temperature setting for whatever I'm actually trying to get.

    On the other hand, the meat probe in my MES40 is dead on, within 1 degree, over its entire range.  So we know that MB CAN get a probe to read correctly.

    If I don't have the meat probe inserted into a piece of meat, I can use it to measure the smoker's air temperature at whatever place I position it.  That's sometimes handy for jerky making, etc.

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