Temperature profiling the OBS chamber

[TestRocket]

I'm thinking of doing a temp profile using 6 or 7 thermocouples placed in different locations within my OBS. I have available a 6 channel thermocouple indicator and a single digital TC probe I could add. I would place all 7 in boiling water and record any difference and adjust the data as needed for the presentation. If the thermometer on the OBS door can be removed I'll check it at 212 degs and if it can be calibrated I'll add it to the data.

My OBS is new with only one 7 hr cook and the original seasoning. My thoughts are to profile the smoke chamber before and after the addition of a second 500 watt element (and PID) just to see any difference. I guess my ultimate goal is to find a way to balance the temperature within the smoking chamber so as to not have to rotate the racks.

I would like to have experienced BS users suggest locations for the placement of the 7 TC's and any other thoughts they may have had in the past but not enough thermocouples to answer their questions. Simulating the cooking load so I don't have to cook exactly the same thing each time I run the test would be a helpful if anyone has an idea for that too.

I just thought of a way to add maybe one or two more thermocouples using a couple of DVM's and Fluke thermocouple converters, so maybe up to 9-10 locations.

Is this of interest to anyone?

[BuyLowSellHigh]

A month ago I did a very pedestrian version of what you are describing

http://forum.bradleysmoker.com/index.php?topic=15591.msg185989#msg185989

http://forum.bradleysmoker.com/index.php?topic=15591.msg186021#msg186021

As far as I am concerned, more info / understanding is a good thing, so yeah I am interested.  My one suggestion would be to do it with step temp changes in both directions to understand what happens when you try to make temp changes.  If I were to do it again today I would also look at recovery after a door opening cool-down - open door for say 3 min's, close, watch drop and recovery.

The only caveat, as I have learned since, is once you put stuff in there everything changes.  It was, however, very helpful to me to understand what goes on inside.

[TestRocket]

I wouldn't call it a "pedestrian" version because I haven't even thought of doing a graph and most days I can put one foot in front of the other. Thanks for the links and something more to think about. As this evolves I may need a few others to help me move forward and I like the way you are thinking!

[TestRocket]

BuyLowSellHigh,

After reading and looking at your data again I see you reference TB as a thermistor. Is your 6 rack smoker the DBS? I was just thinking if I couldn't calibrate the installed thermometer on my OBS I could place a TC at that location and that your thermistor should be more accurate then my dial gauge.

[BuyLowSellHigh]

Yep - as far as I know the Six racks have only been offered as digitals, and the installed sensor is a thermistor.

Since the DBS is designed to control temps thermostatically, vs a power input control on the OBS, I wanted to understand the accuracy and time constant associated with the installed sensor.  I think your issue in the end with the OBS will be what happens when start loading the racks, which will probably render the installed thermometer pretty useless.

If you really want to study this you might consider using dummy loads - maybe bricks.  I think the most informative would be to profile the smoker unloaded and get step temp change data both up and down.  Then do the same loading someting in the 5-10 lb range that is at room temp when introduced (smoker preheated). Then do the same load again on a different rack.  Do that for say 3 racks, then do a combination of 2 racks.  That would be fairly exhaustive, but it should give a pretty complete picture of how heat moves within the tower under different conditions.

[classicrockgriller]

Wouldn't installing a fan kit help balance the temps? It did on mine to the point that I'm happy.

[BuyLowSellHigh]

That was my thought too CRG and I did it this week.

[Habanero Smoker]

The door thermometer can be removed, and I believe calibrated. Most analog probes have that capability. There have been many posts on the temperature variance, and tests done to understand the variances. The temperature varies not only for top to bottom, but also front to back. So keep that in mind when you place your probes. That encouraged Olds to develop the circulation fan.

It's a good idea to test it both empty, and with a simulated load. When I want to simulate a load, I use a couple of disposable pans, 4 pounds of sterile sand, plus a pint of water in each pan to simulate about 10 pounds of meat.

[pensrock]

I was going to bring a temp profiler from work home and do a profile also but now that I have got used to rotating the racks and I have no plan to add a fan to help even things out I gave up on the idea. IMHO the fan should help a lot.

[TestRocket]

About adding the fan, has anyone added it along with the second 500W element and felt it is doing the job and is it the 35CFM? The last thing I can remember reading on the fan issue is it was only recommended for the single 500W element.

Some great points to keep in mind and Habanero the sand and water idea is one I'll be using.

Thanks all.

[KevinG]

I do some oven temperature profiling at work, we use a 10 probe system. It's hard to describe the positions we put them, but I'll give it a try. Open the door and on the left side place 4 probes, one on the top front, top back, bottom front, bottom back. Do the same for the right side of the oven. The two remaining probes go in the center of the oven one near the top and one near the bottom (both of these are relatively close to the center of the oven and even gapped between the top and bottom).

[classicrockgriller]

I have a 6 rak with both elements and fan, and an obs with single element and a fan.

[KyNola]

I thought profiling was illegal.

[KevinG]

You haven't seen the news about AZ lately have you?

[BuyLowSellHigh]

I thought profiling was illegal.

Depends on who is being profiled by whom.   8)