Has Anyone Fooled the MES Temp Sensor Before?

Discussion in 'Electric Smokers' started by tallbm, Dec 30, 2016.

  1. tallbm

    tallbm Master of the Pit

    Hi everyone, I'm new here and just posted in Roll Call about 5 minutes ago.

    Has anyone found a way to fool/trick the MES temp sensor so that it reads about 30 degrees cooler than normal?

    Why am I asking this?  Well read on below for many long and boring details :)

    My MES40 reports 275 degrees while my Maverick reports 245 degrees where my meat is and the MES then cycles off the heating because it believes it has reached 275 degrees.  There is a 25-30 degree difference all the time.  

    This means I can never get over 245 degrees to hit 275 degrees for many good cooking reasons (hotter smokes, crisping skin, meat bark, etc, etc.).

    I have searched a ton on this site over this issue (via the search feature, and via targeted Google searches isolated to "site:smokingmeatforums.com") and found many people talking about this common MES problem and many people troubleshooting to get to the root cause.

    What I haven't found is anyone saying something like

    "To fool the MES sensor so it reads 20 degrees low, just wrap the sensor in a ball of foil and that will do."

    I'm looking for a quick simple "work around" fix so I can have the MES read 30 degrees low thereby allowing a REAL 275 degrees read by my Maverick instead of hitting the current upper limit of 245 degrees.  

    I intend to let my Maverick alarm notify me of the actual temperature at 275 degrees and adjust the MES temperature to hold as appropriate.

    For more Info on my setup see the following work I have put in so far:

    -Applied 12"x12" ceramic tile heat sink fix to even out temps inside smoker (did this after testing 4 probes in various areas and having different results, after tile fix applied 

    -Applied mailbox cold smoking mod

    -Using an AMNPS (not tube but tray)

    -Using Maverick ET-733
    Last edited: Dec 30, 2016
  2. smokinal

    smokinal Smoking Guru Staff Member Moderator OTBS Member ★ Lifetime Premier ★

    As you have read this is a common problem with the MES.

    Some guys luck out & the MES controller will say 275, but the temp is really 300.

    In your case it's the opposite & the only thing you can do is contact MB customer service & they will probably send you a new controller.

    Hopefully you will get one that is more accurate or at least is inaccurate in the right direction.

    Good luck!

  3. tallbm

    tallbm Master of the Pit

    Thanks for the info.  I'll play with covering the sensor a bit while I contact Masterbuilt and see what they say about a replacement control unit :)
  4. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Put a therm in the exhaust hole and check the temp...   The MES smokers have terrible homogenized heat...  there are hot zones, cold zones etc...
    daricksta likes this.
  5. tallbm

    tallbm Master of the Pit

    Good idea.

    During the break in I tested 4 areas across the smoker and had big temperature variances as most report.

    I then applied the 12"x12" ceramic tile heat sink work around and that evened things out quite a bit. 

    I'll put a probe in the exhaust hole and see what it is reporting now.

    I'm also going to take a small piece of mesquite or oak or some type of seasoned smoking wood and drill a hole the size of the sensor and put it over the sensor and see if I can figure out how to trick it a little bit while using my Maverick to help me manage the real temp.

    I don't plan to go crazy but I figure covering partial way, and/or using a few different pieces/sizes of wood may be some interesting experiments to see what happens.  Again, I plan on doing this safely while using the maverick and other probes to see whats going on in the box.

    Thanks :)
  6. bearcarver

    bearcarver Smoking Guru OTBS Member

    If you're only getting 245° with an Accurate Maverick when it's set for 275°, like Al said, call Masterbuilt, because you paid for a Smoker that goes from 100° to 275°.

    To check for sure, before you call them, Boil test your maverick smoker probe, and then put it very close to the Heat sensor on the back wall (looks like a little toggle switch). That should show how close the MES is to your Maverick.

    If it's not as bad as you thought, just put the Maverick probe near your food, and adjust your MES until the Maverick reads the temp you want.

    I don't know why anybody would care what the temp is in your top vent, unless that's where you put the meat.

    Once you test & find your Maverick to be accurate, ALWAYS trust your Maverick---Not the MES readout.

  7. tallbm

    tallbm Master of the Pit

    Thanks for the advise.  I'll be sure to do the boil test before calling them.   I hope they send me a control that is more accurate or has the opposite problem where it reads lower than reality.  That would be nice for crisping chicken skin :)
  8. pa42phigh

    pa42phigh Newbie

    My smoker is 3 years old I had this problem to my smoker was running cooler that it was saying and it would stop calling for heat I unhooked the snapdisk or high temp control while not safe apparently this was cause of the problem working fine now
    Last edited: Jan 3, 2017
  9. floridasteve

    floridasteve Smoking Fanatic

    I did that, and they sent me a new controller, but it didn't fix the problem.  What I'm finding is that if I set the temp at 275 and put probes in various locations in the smoker, they all read close to 275 UNTIL i put something on one of the racks.  Then, the probes on that rack and above read 30* low, while those below the rack read 275.

    I tried putting a large piece of 1" thick granite on the bottom shelf to act as a defuser to send the heat up the sides, and to also act as a heat sink, but that did nothing.  It's got to be heat distribution management.  I've got a couple cheap USB fans -- I think the next time I'm doing a long cook I'll try blowing some air in the chip shoot, or sucking the exhaust out faster, or just circulating air around inside the chamber.

    For now when I cook birds, I use my mini. LOL

    Oh, I have a 1 yr old gen 2.5 and just replaced the heating unit.  I always run it with the chip tube a couple inches out and the exhaust wide open. I have a dual probe Maveric and a 4 probe i'grill, all checked in boiling water.
  10. tallbm

    tallbm Master of the Pit

    I'm not sure I"m going to start unhooking the sensor just yet.  I did have the idea of wiring it into a probe but I don't know enough about the existing system to know if the controller would read a probe the same way it does it's current sensor.  If that were the case I could buy a 6ft replacement probe, wire it up and then I could have a probe that measures heat wherever I put it.  So if It's at the top rack, bottom rack, upper left corner, etc. etc. The unit would reflect the temp where I needed it to be measured.

    Sounds like a great idea in theory but again that is a lot of speculation, research, and one potentially damaged unit leaving me without a smoker and a hole in my wallet :)

    I do the mailbox mod so no fans blowing into the unit for me but if you do it please report back with your findings.

    It dawned on me about 10 minutes ago that instead of using a piece of wood over the sensor I could use a wine cork.

    I could much more easily modify a wine cork than a piece of wood and all I need to do is drink more wine to get more corks to carve/cut up and work with :D

    I won't get to do any of this until the weekend though and not until after I make my first attempt at Ground Formed Bacon which I plan to do this weekend.

    Man this is all exciting stuff.  So many firsts for me and so many little projects :D
  11. bearcarver

    bearcarver Smoking Guru OTBS Member

    Don't know if that's any help.

  12. dr k

    dr k Master of the Pit

    I have a Mes 40" gen 1 and I use a deflector between the sensor and the heating element so the heat doesn't go up the back wall past the sensor out the top vent.  I raise my empty water pan and it is an obstacle to even out heat on the second to the top rack.  The water pan can be placed at any level.  It's a vertical smoker with 4 to six racks and whatever rack the Mes sensor is closest to should be the closest to the Mes controller temp.  But most likely not and then you have the other racks the sensor is no where near.  But people go by calibrated air probe placed next to the food.  I use the deflector in the pic below and elevate the water pan for even heating on the top two racks. 

    Fold in half and put in the corner above the heating element

    I'm happy with my results but may raise the water pan to the second from the top level and experiment. 

  13. tallbm

    tallbm Master of the Pit

    Thanks for the info Kurt.  I am using the 12"x12" ceramic tile mod which I believe is similar to your deflector.  I have the tile on top of the chip feeder box putting the tile between the heating element and the MES temp sensor/thermistor.  I did not have the the water tray in, I've removed that according to what I read with some of the deflector and tile mod posts.

    I did quite a bit of research today and found some amazing work done by guys that have posted on this forum.  

    Basically I am convinced that the sensor/probe/thermistor that Masterbuilt uses for the controller is simply cheap and and has a high margin of error.

    The user Sigmo did some good testing here  http://www.smokingmeatforums.com/t/...eading-on-display-higher-than-actual-temps/20

    While the user ForageFish went a step beyond basically performing the same test as well as checking the voltage here http://www.smokingmeatforums.com/t/139353/mes-controller-reverse-engineering

    Additionally ForageFish put together a solution that seems to confirm that Masterbuilt just uses a poor thermistor for the contoller temperature.

    ForageFish actually increased the resistance of the thermistor circuit in a clever way to basically correct the flaw.

    I'm no electrical engineer, electrician, or a hardware circuitry designer so any of you guys that happen to be one please feel free to correct anything I may misstate, but I believe I can translate what I have found into the following.  

    Info from Posts Explained:

    The thermistor (sensor/probe) that the MES controller uses is so poor that it does not behave to the specification it is calibrated to thereby reporting a higher temperature than reality.

    Best analogy I can give that you buy a 12 inch ruler and you use it to measure stuff and then find out that the last 2 inches of the ruler are not calibrated properly and lead to a ruler that is 11.5 inches in length though it is reporting/claiming 12 inches in length.  Doh!!! 

    Since the MES thermistor seems to be an NTC type resistor (it appears so according to ForageFish's research and solution) the resistance lessens as the temperature around the thermistor goes up but get's faulty after certain temperatures because the resistance of the thermistor/resistor is not working as defined in the specification.

    ForageFish's solution was to test temps all probe temps, capture Ohms of the thermister circuit, use the data to do the math and figure out how much resistance needed to be added to the MES thermistor circuit to get the near correct reading sent to the MES controller.  With the MES thermistor resistance about corrected the MES controller temp would be very close to the real temp reported by his Omega probe.  

    His solution wasn't full proof as the faulty thermistor with added resistance would report about 10 degrees higher at ambient temps but I don't think that is an issues.  It is simple to dial up the temp 10 degrees than reported higher at such low temps. 

    ForageFish increased resistance to the MES thermistor circuit by adding what appears to be an SMD chip resistor in parallel to the existing resistor on the MES controller board.  Well it looks like an SMD chip resistor but don't quote me on it and feel free to confirm the exact type of resister added on your own :)  

    So in short the solution was to get closer to the defined/proper specification (resistance) of the MES thermistor so it would report properly.

    In my mind I think replacing the MES thermistor/probe/sensor with a new NTC thermistor/probe/sensor that is more accurate or in a better resistance range would solve the issue as well.

    So basically replace the bad thermastat with a good/better one that is compatible.

    In Conclusion:

    I still plan to reach out to Masterbuilt but seeing all this information I don't think they are going to be able to do do much other than send a new unit unless they want me to replace the thermistor/probe/sensor myself with one they send me.

    I still plan on messing around with the cork idea.  Hopefully I can insulate the MES thermistor/sensor/probe so much that I can hit higher temps in my MES.  I will simply and regulate the temp manually on the controller according to what my Maverick reports.

    Let me know if all this info makes some kind of sense lol.

    Again, please feel free to correct anything I may have misstated and I will correct the info.  I don't want to be putting bad or misleading info to be out there in the world for other people to stumble over :)
    Last edited: Jan 3, 2017
  14. tallbm

    tallbm Master of the Pit

    Update:  Yesterday I called Masterbuilt support and the guy asked a few questions about my issue.  I gave him my model number and told him when/where (Nov 2016/Academy Sports)  I purchased the MES and after looking he said "it is a controller issue".

    I understand that customer service reps are not techs and such so I was skeptical about his answer so I flat out asked him..

    "So is this a known issue with the models sold around the time I purchased mine?"

    His answer was "yes".  He said for me to reply back to his email with my serial number (won't have that until this weekend) and the model number and they will send me out a new controller free of charge.

    I am still skeptical that a new controller will fix the issue but only time will tell.

    In any case with two controllers I can play around with ForageFish's chip resistor mod and see if that "fixes" the old controller.  If so I will have two working controllers in case one craps out after the warranty!

    I'll keep you guys posted :)
    Last edited: Jan 5, 2017
  15. I recently got a Gen1 MES40 and was having the same problem as the OP. I could tell the temperature was not right so I purchased a Maverick and sure enough, with the control set on 275, the best I could do on the second shelf was 245. Did some pondering and experimenting and came to the same conclusion as Dr K. The drip pan on the fourth shelf forces the heat flow to the back wall, then up to the sensor giving a higher reading than the middle of the cabinet. I moved the drip pan up to the third shelf and success, the control now reads within 5 degrees of the Maverick probe on the second shelf. That I can work with. I think giving the rising heat a larger initial air mass before deflection causes more turbulence within the cabinet and evens out the temperature rather than the heat racing toward the vent along the walls.
  16. bearcarver

    bearcarver Smoking Guru OTBS Member

    Generally speaking the biggest problem with the Gen #1 was the fact that the heating element is on the right side, and so is the top vent.

    So the heat would come from the right half of the smoker & run straight up the right side & out the top vent on the right.

    That would make the right side hotter than the left.  I solved this years ago, by putting a piece of metal (Heat deflector) on the right side, just above the water pan in it's normal position. This would push the heat from the right to as far to the left as I wanted, by a simple adjustment to that heat deflector. I did this for 4 years, until I got my New Gen #2.5 MES.

    The water pan had little to do with this---It was the fact that both the heating element & the top vent were on the right.

    I told Masterbuilt about this problem years ago & they moved their top vent to the left side---Problem Solved !!!

  17. dr k

    dr k Master of the Pit

    Your the first person that moved the pan up since I've been posting about even heat on the top two racks. Since I use the mailbox mod I removed all the chip tray metal above and below the heating element. My heating cycles shortened since I no longer have a heat sink. Now outside air flows in over the exposed element, mixes then rises then has to go around the elevated water pan. If your cooking on the top two racks, then you have to create chaos as the air rises so predictable currents rivers of air aren't so prevalent. If you have a full smoker the food has you covered.
  18. sigmo

    sigmo Smoking Fanatic

    The problem with insulating the temperature sensor is that, ultimately, it will not achieve what you want (a different calibration of the sensor).  All it will do is alter the speed of response of the sensor.  It'll just slow the response down.  And you don't really want that.  Slowing the sensor down will result in larger temperature swings because the heater will stay on for longer periods and stay off for longer periods.  You really do want the sensor to respond rather quickly to get a "smoother" more even temperature (over time) in the smoker.
    That's more like it.

    As many of the posts have pointed out, even if the sensor is accurate, you'll get hot and cold spots in the smoker if the heat isn't evenly distributed.

    Having the sensor positioned directly over the heating element has good and bad aspects.

    The good is that it speeds the response of the system, resulting in more rapid cycling of the heating element, giving a more even temperature in the unit.  It's also something of a safety thing, too, because it assures that no part of the smoker is likely to be too hot.   When we block the sensor's ability to "see" the heat, we get higher temperatures and perhaps larger swings in temperature.

    The bad is that the sensor "sees" the heat coming right off of the heating element, so it overestimates the temperature in the rest of the smoker.  And this is the goal of people installing baffles and such to prevent the sensor from being in the direct path of the heated air rising up from the heating element.  Again, there are pros and cons to anything we do, so it's just good to think about it and be careful to get what you really want.

    Yeah.  This gets to the problem, too!

    Ideally, we'd have much better mixing of the air inside the smoker so the smoke and temperature would stay very even throughout the whole volume.

    But these are inexpensive devices, and there's only so much they can do.  And as folks have pointed out, the way you load the food into them, any baffles we put in, etc., all change the dynamics.  Every time you smoke something, the way you load the food in changes it all.

    I've read a bit about commercial smokers, and the various manufacturers often talk a LOT about their systems for directing the heat and smoke to try to get very even cooking and smoking.  Often, things are fan-forced, and even have moving baffles that shift the direction of airflow constantly to get even cooking and smoking over the entire volume of the smoker so that the products are cooked and smoked evenly.

    But those smokers cost a LOT, I'm sure.

    Without active stirring of the air in the smoker, you just have to try your best to baffle things and load the food to get the heat and smoke to be as even as possible.  I tend to use disposable foil steam-pan covers and the like as baffles that I can put in place and move around depending on the sizes and shapes of the foods I'm smoking to always try to even things out.

    I just got a used fan for a convection oven that I will likely try to "kludge" into my MES 40 at some point.  I will likely set up a controller to cycle it on and off so it's not blasting the air around inside of the smoker too badly, yet keeps things stirred a little better.  That's going to take some experimenting.  Keep in mind that this fan will only stir the air within the smoker.  It's not going to force air into or out of the smoker.  I'll either stay with convection for that, or add some different kind of fan setup if I decide that needs to be forced.

    First things first, I guess!

    Fancy laboratory drying ovens and incubators, and fancy commercial smokers seem to all employ some kind of active stirring of the air.  And if I was going to build my own smoker, I would use a design based on a lot of those ovens I've seen that use the side walls as air plenums, with perforations that force the air to flow horizontally across the chamber from one side over to the other (one side sucking, the other blowing, with the heater in the air path, but hidden).  But for now, I just want to see if I can make my existing little MES work a bit better.

    Once I figure out what I'm going to do, and actually make some progress and have something to report, I'll make a thread about it.

    Part of the modifications will ultimately be to use a different system entirely to control the heater based on more accurate temperature sensors.

    But again, the first step I want to try is just actively stirring the air in the smoker to try to get more even heat and smoke.

    This is an interesting thread, and touches on a lot of things we all seem to run up against with these smokers.
  19. tallbm

    tallbm Master of the Pit

    That is great input Sigmo!

    I just received confirmation from Masterbuilt that my new controller unit is on the way so I will have that to toy with myself.  I also bought a flexible ducting hose to try and "duct" the exhaust from the opposite side of where the vent/damper is currently located.  This would have the air flow across the smoker rather than straight up from element to vent/damper.

    Lots of experiments on the list lol.
  20. floridasteve

    floridasteve Smoking Fanatic

    Thanks Bear. You confirmed what I suspected. Now to figure out a way to get the heat to distribute. I fan inside the unit stirring the air up would probably be best, but I couldn't imagine it lasting very long. LOL

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