Thermometer inaccurarcies.

One of the nice things about doing a brewout with others is that it is an opportunity to examine your practices, set-up and equipment.

A few weeks ago, I did a brewout with desertBrew in Tucson and as a result we were able to figure out some problems with temperature readings. The first problem was a flaw in my set-up combined with a touch of operator error.

My set up uses a BrewMometer (or Milijoco, or similar) dial thermometer in conjunction with a sight-glass on the same coupler using a tee.


http://www.blichmannengineering.com/BrewMometer/BrewMometer.htm


We found that the water temperature in the tank can vary up to 15°F. (Bear in mind this is in HOT weather, If it were cold outside, I'm sure the range would be greater.) Your best bet is to stir the water to get the best reading. It seems pretty intuitive now as the termometer probe only extends a few inches from the dial. (A head slapping momement for sure!)

I'm willing to bet that you'd still get quite a variation in temperature even if the thermometer went directly into the coupler. You may want to make sure your water is stirred or you may get a pretty inaccurate reading.

Now I know why it was so hard to hit my strike temps!

Ths second realization was how much variation there was between thermometers. We used a BBQ thermometer, the dial thermometers mentioned above, a couple of analog thermometers, and a digital.

By using each other's thermometers we were able to "cross-calibrate" our temperature readings and determine how consistent our readings thermometers were. Still. I think that I would like to get a better thermometer

Here are the two I'm thinking about:
Thermapen vs Traceable

I think that the Traceable has the obvious cost advantage, but has anyone actually stuck one on a keggle? Will the suction hold on the inside and the outside? I also saw no stats for the speed of readings.

I like the Thermapen for the speed factor and accuracy. However it will be a drag to have to keep taking readings. Cost is higher, but I'm OK with any cost if it is the right tool for the job.

Thoughts?

Good point about stirring the water.

My LHBS sells what he calls a calibration thermometer. Fairly inexpensive if I recall correctly somewhere in the >$10 neighborhood. I used that to adjust the Milijoco type and used a Sharpie to write what the differences were on the digital thermometer.

I'll ask Doug about the calibration thermometer and get a more accurate price when he comes back from vacation this weekend if you'd like.

I would love either one of those thermometers that you've linked to, ollllllllllllllllllllllllllllllllo. Couldn't tell you which is better, though.

Can't remember - do you have any offspring? If affirmative, got a nice holiday coming up in a few weeks, time to start dropping hints...

I had thermometer calibration issues this weekend, wish I had one of those Traceable thermos. If anyone has used these, please post, as I think I must have one!

Currently brewing and still wondering who's thermometer was accurate.

Since I busted my digital I'm still using the little analog bugger and I want a quality one next too. $85 is a bit more than I'd like to spend though. I'll be prowling this thread for a good compomise.

True about stirring to get an accurate reading.

I use a digital probe thermo in both my HLT and MLT. Brewed for the first time with them last week. Loved 'em!!! I need to figure out a better way to attach them to the kegs and cleanly keep the cords out of the way.

They're just cheap $15 units from Walmart. They seem accurate. I've tested them against each other and two other thermos I've got. They also seem to be waterproof, not like the kinds with the exposed braids. Before I got the thermosights I just let them hang down in the water and mash with no problem.



And the thread about how I installed them: https://www.homebrewtalk.com/showthread.php?t=28815

From what I understand, a calibration thermometer (liquid sealed) will work, albeit with considerably more response time than the digital one's I linked to.

Please don't do the $$/second math. I know that I am l buying a toy... errrr high-end tool.

No progeny, the_bird, but it was a nice thought.

About thermometers, here's something I found out this weekend;

Had someone ask me what temps we kept the store, so I went over to the thermometer shelf. Pulled out a handful of those cheap floating therms, and looked at the readings on them. 76, 78, 80, 78, 76, 80. (One was 82.) Yep, there were few repeats, and covered a 6 degree range. Makes 1 1der, doesn't it?

The other more expensive ones were better, but still not as good as I'd want.

steve

skou said:

About thermometers, here's something I found out this weekend;

Had someone ask me what temps we kept the store, so I went over to the thermometer shelf. Pulled out a handful of those cheap floating therms, and looked at the readings on them. 76, 78, 80, 78, 76, 80. (One was 82.) Yep, there were few repeats, and covered a 6 degree range. Makes 1 1der, doesn't it?

The other more expensive ones were better, but still not as good as I'd want.

steve

Click to expand...

Skou, your only option there is to report that the temperature was 78.6 +/- 2.2 degrees at the 99% confidence level. Sounds like a accurate measurement to me...

Lil' Sparky I believe I have the same exact thermometer as you, the one thing that you want to be careful of is that no part of the probe is touching your keggle, it gives em crazy readings. I looked at your set-up and the look like they're insulated but it's something to keep in mind.

I just check my two digital therms against one another at room temp prior to brewing... they are always within1 degree of one another, and that is all that I can hope for. My probes reach almost to the middle of the MLT and HLT.

pfranco81 said:

Lil' Sparky I believe I have the same exact thermometer as you, the one thing that you want to be careful of is that no part of the probe is touching your keggle, it gives em crazy readings. I looked at your set-up and the look like they're insulated but it's something to keep in mind.

Click to expand...

Thanks for the tip. I'm using a piece of silicon tubing to seal the probe in the compression fitting. It doesn't touch any metal. This thread shows what I did. https://www.homebrewtalk.com/showthread.php?t=28815

You weren't talking about the wire, were you? It's completely sealed in silicon, and doesn't make any difference if it touches anything.

Levers101 said:

Skou, your only option there is to report that the temperature was 78.6 +/- 2.2 degrees at the 99% confidence level. Sounds like a accurate measurement to me...

Click to expand...

Accurate? yes.
Precise? no.

I calibrated mine against ice water and boiling water and they were spot on. I use cheap digital meat thermometers. In the past I've had to add a fudge factor to get an accurate reading.

ice bath/boiling water calibration is always a good idea.
Though personally I keep my meat probe away from fudge...

dantodd said:

... I keep my ... probe away from fudge...

Click to expand...

WAY too much information....

Can this be filed under "homebrew terms that sound dirty?"

As I have been an impatient bastard lately, I went ahead and ordered the Tracable unit as well as some other gizmo's at Professional Equipment.
(You can't order just one item... you need to justify the shipping...)
I'll post my results.

No guarantee that I won't also order the Thermapen at some point.:cross:

olllllo said:

As I have been an impatient bastard lately, I went ahead and ordered the Tracable unit as well as some other gizmo's at Professional Equipment.
(You can't order just one item... you need to justify the shipping...)
I'll post my results.

No guarantee that I won't also order the Thermapen at some point.:cross:

Click to expand...

I see they sell PH meters, as well... that's the "toy" that I would love to have, although I hate the idea of having to buy new probes regularly.

I actually got a USB data logger to log temperatures in various parts of my home.
I also want to kow how (in)efficient my fridge is in the garage.
I was contmplating the ph meter, but I know that someone on this site has a recommendation for that.

I hope.

Glad I did a search and found this thread. I'm also looking for a new thermometer. I've been using the dial one that came with my turkey fryer, a so-called accurate dial thermometer I got at Target, and my trusty old Target $9.99 digital thermometer.

olllllo said:

I think that the Traceable has the obvious cost advantage, but has anyone actually stuck one on a keggle? Will the suction hold on the inside and the outside? I also saw no stats for the speed of readings.

Click to expand...

I have one of the Traceable thermometers and used it for the first time a couple weeks back when I did my first AG. It worked well and I was happy with its performance.

According to the documentation that came with mine it has a 1 second sample rate. I can't comment on the suction cups because I didn't use them. Instead, I just draped the cable over a piece of copper pipe I had across the top of my brewpot and suspended the probe in the middle of the liquid.

Forgot to update this.

The traceable thermo rocks. It updates every second in .1 incriments.
The suction cup is useless on the inside, but hey.

I found that my BBQ thermo is only off by a 1/2 degree maybe.

Stirring the HLT water is key when using the bi-metal analog thermo as mentioed above.

I'll post more with pictures and reviews of the other stuff I bough.