Sunday, February 5, 2017

A Man With Two Watches Never Knows What Time It Is

That's one of my favorite modern proverbs, one with which almost everyone can identify - at least if you remember depending on a watch without instant access to "atomic time" through your cellphone connection  (most of the great, older proverbs come from the Bible's book of Proverbs).

That's prompted by something that happened today.  I was up an hour before sunrise to get a pork butt into the smoker.  No, it has nothing to do with the Super Bowl, it was just time to do some experiments with my smoking setup.  The smoker was preheated and the butt went into the smoker by 7:00 AM.  I put two temperature probes into it, the built in temperature probe and my new remote reading thermometer.   That's where the problem showed up.
The pork butt was rubbed and left in the refrigerator overnight, as always, so it was cold.  The built in probe (on the left side of the meat) said 37, the remote probe (on the right) said 29.  That puzzled me.  It was out of the freezer long enough that we thought it was thawed before it got rubbed and put in the fridge.  I thought it might really just be a cold spot, so I'd keep an eye on it.  As the morning went by, the two thermometers diverged.  By 10:00 they were getting to be 70 degrees apart, almost 40 and 110, an enormous thermal gradient for probes a few inches apart.  What's going on here?  Is either one right?

Well, what would you do?  In this case, I have other ways of measuring the temperature as long as I don't leave them in the smoker (where the chamber temperature is about 240).  A quick check showed the "independent" thermometer pretty much agreed with the other two.  There really was that big a temperature gradient.  In the intervening hour and a half, the difference has gone down.  It's now 147 and 134.  I suspect that by the time we reach pulling temperature late in the day that difference between thermometers will go down to a couple of degrees.

Now the real purpose of this experiment was to investigate that little chamber on the right, an external smoke generator that I first talked about New Year's Eve.  As I said in that little piece, one of my main reasons for getting this was that they claim it can produce smoke for "up to 6 hours", which would make an overnight smoke for something like a big beef brisket much more bearable.  My experience on New Year's Eve was that it only ran for perhaps two hours, and I found that the wood chips would stick in the chute inside the smoke generator requiring a poke with a long screwdriver to get them to drop onto the heater.  So far, it seems to be doing the same thing.  I had to poke at the chips around 1-1/2 hours into the smoke, and I did it again at around 3. In retrospect, I should have let it sit longer to see if the smoking then stopped, or just became thinner.

And while I'm on the topic of that cold smoking attachment, we tried the cold smoked cheese on Friday as a "birthday treat".  That was just slightly over a month since we smoked, vacuum sealed, and put it in the refrigerator.  It was fantastic.  There's one block of cheddar we smoked and haven't opened.  Some of the guys on the forum I read say they won't touch it for a year.   I don't think I could make that.

1. Nice setup, the wheeled cart and ratcheting tie down. Makes moving things much easier.

I look forward to the series of blog posts on diagnosing and upgrading the external smoke generator. ;-)

--Ed

1. You can see a set of double doors in the background. There's a part of a sheet of 1/2" plywood that's the ramp to get in and out of the garage. If you look closely, you'll see there are double thicknesses of that 1/2" plywood around the edges - that's an attempt to make it harder to slide around on the cart. I'll find out how well that works tonight.

As for the chip dispensing, maybe a small (NEMA17) stepper motor with a little programmable timer that pushes some chips into the side of the smoker every so-many minutes.

My desire to sleep all night is outweighing my desire for brisket. ;-)

2. As a mechanic, I have five tire pressure gauges. I have at least five ways of measuring electricity accurately. I have two compression gauge sets. I have multiple micrometers, and vernier calipers. I even have three ways to measure temp in my pork butts.

Why? To get a good number I can reasonably trust. I have no compunction at all to taking one out of service, correcting it, or even just throwing it out if I can't trust it.

1. Carteach, I'm not aware of any long lost brothers, but you could be one.

3. Thanks for the cheese update. I was thinking about it just last week.

Stepper motor and controller? Did you ever work for Lockheed? See L1011 lav computer.
(We actually called it the crapper computer)

1. LOL, no - never Lock-Mart. I was thinking like another homebuilt CNC system; Arduino controller driving a little stepper motor. There's a million and six versions of that out there.

2. In all fairness to Lockheed I should point out there were 6 lavs across the aft pressure bulkhead in coach. You did NOT want all of them to flush at the same time.
And best autopilot ever.

4. Take a glass of water and put 3 ice cubes in it. Fill it with water to just above the ice cubes. Wait until you see the ice cubes have melted a visible amount. The water is now 32 fahrenheit, and will remain at that temperature as long as there is ice in the water. Place thermometers in glass to check accuracy

1. But to be reasonably confident, you had better also boil a pot of distilled water (SiG lives near sea level) to get the 212 point. Otherwise there is the real possibility that your one point cal may be good, but doesn't scale as the temp gets higher. Of course, non-linearity is also a possibility, but two points is usually sufficient.

5. Instead of a stepper motor, I wonder if I could use a motor from an old discarded electric can opener, and set it up to drive an auger or something like that?

1. Oh, sure. There's any number of ways of getting this done. It's just kind of a running joke that the answer to every question is a stepper and a microprocessor.