Concerns on MES 130

[Bearcarver]

MES temp setting started at 225. Now set for 235, readout says 237, but thermometer inside the smoker is at 200. I don’t know if there’s water in the pan; hubby set it up and went fishing.

OK---The Temp inside a smoker varies from one area to another.
The important thing is what the Temp is at the place your Meat is.


Bear

 

[sigmo]

Keep in mind that the temperature probe for the MES (at least my gen 1 MES 40) is located right above the heating element. So it "sees" a higher temperature than a probe placed elsewhere in the box will see.

Without a fan to stir the air in the smoker, you will see large differences depending on where a thermometer or probe is positioned.

Years ago, when I mounted a small thermocouple directly to my MES's temperature probe, I found that there were still errors in the MES readout. But they weren't as great as what I observed when I measured temperatures with a sensor placed far from the MES's sensor.

This is especially true when you have a big piece of moist, cold meat in the chamber. At that time, I speculated that there may well be a method to Masterbuilt's madness.

Despite the lack of apparent accuracy, I still have not modified my MES's temperature control system, and I get good results, with cooking times to meat internal temperatures that match well with other people's on the forum.

I do, however, use an Amazin pellet maze for my smoke source. The chip burner of the original MES never did give me consistent or adequate smoke.

The meat probe of my MES tested to be surprisingly accurate, and I always use it with confidence.

I tested the MES meat probe with the dry block temperature calibrator that I built years ago to calibrate laboratory thermometers and data acquisition system probes. This relies on using a NIST certified reference thermometer.

I tested the MES's chamber sensor with a thermocouple and readout that I had calibrated in that temperature calibrator.

Testing temperature probes and readout systems should be done carefully, realizing that just having them in the same oven or smoker is not enough to keep them at the same temperature. We routinely observe differences of 15 degrees C (27 degrees F) between locations only a few inches apart in expensive laboratory ovens.

Unless an oven or incubator is vigorously stirred, that's to be expected. And even well-stirred ovens will show surprising variations from place to place.

Also consider the speeds of response between different probes and displays.

 

[Jonok]

Another thing to consider is that the energy in an empty smoker with a single radiant heat source is largely IR "trying to find something to heat up".
If you just have a little bitty probe floating around in the air, it's going to be different than a probe that's sitting just right on a grate and being heated by conduction. I fabricated a bunch of small aluminum blocks to stick my temp probes in to measure chamber temperature. They're big enough to absorb IR and sit on a rack reliably, but small enough that the aluminum will rapidly equilibrate with its surroundings and help the probe provide meaningful data.

 

[sigmo]

That's a good point and a good idea.

When I built temperature probes for refrigerators, incubators, and the like for some laboratories, I had a friend machine special aluminum housings for the sensors.

These were then anodized blue for corrosion resistance, looks, and to achieve a consistent thermal emissivity.

The resulting probes were usually mounted to a relatively non-conductive surface, or separated from a conductive surface by an insulator.

The surface area to mass ratio (and taking into account the specific heat of aluminum versus water) was designed to simulate the thermal time constant (in air) of a 40ml VOA vial full of water. Since this was a typical container for samples, we wanted the data acquisition systems to plot temperature swings that approximated the temperature swings the actual samples experienced as refrigerator compressors or heaters cycled.

The thermal emissivity and the surface area to mass ratio as well as the specific heat of a probe housing all affect the thermal time constant and susceptibility to IR influences. It's really non-trivial, and sometimes counterintuitive.

If your heating element can "shine" directly onto a temperature sensor, you will really see the effect of that radiation!

 

[Jonok]

Well, the drops of 1x2 6061 that I get at my local Alro for $3.00 a pound end up doing pretty well after I glass blast them and run them through a couple smoking cycles. It really is amazing how much less noise there is with 50 gm of "black body" thermal mass...