Thermometer - Checking Accuracy!

[Likesspace]

Well I found something this weekend that really has me ticked off.....
About a year ago I purchased a large dial analog thermometer from one of the cheese making supply stores and immediately fell in love with it.
Before that time I had been using a very small dial thermometer with a short probe and no way to hang it in the cheese vat, so this thermometer seemed to be the perfect solution.
Well last week I decided that I wanted to purchase a Taylor digital thermometer so that I could use one thermometer in the milk and the other in the water bath and this digital model arrived in the mail yesterday.
Well upon reading the manual I noticed that this model can be calibrated so I figured I might as well give it a try. The procedure was the calibrate at 32 degrees F, so I set everything up and gave it a check.
The Taylor brand actually showed 31.9 degrees by using the procedure in the manual and quite honestly that was close enough for me.
Now what ticks me off is that while I had to solution of water and ice made up I decided to check my large dial thermometer as well, and guess what........It was OVER 10 degrees off!
I checked and re-checked and even compared the two under higher temperature water as well. In each and every case the thermometer that I have been using is over 10 degrees off of the new one.
Just to verify that the digital model is reading accurately, I took my small dial thermometer and compared it against the digital. In every single test the small dial and digital were within less than a degree of one another.
So basically I don' t know what type of cheese I've been making with this old thermometer.
I know that I've probably been adding my cheddar culture at about 75 - 80 degrees and have been cooking it to only about 85 - 90 degrees. What gets me is that the cheddar cheeses I have been making are actually coming along nicely in fact I have one that at a little over a month old is a really fantastic example of mild cheddar. (shrugs)
Anyway, I just thought I would pass this along.
I have no idea if this thermometer was faulty the day I received it or if it has lost calibration over time, but from now on I will be checking the calibration of my thermometer before each use, just as I do my Ph meter.
As long as I've been making cheese I should have noticed that the milk was not as warm as it should have been but I just blindly relied on what the thermometer was telling me.
Oh well, live and learn.

Dave

[Boofer]

I've had very inconsistent results with the three digital thermometers I have. I might have expected inherent inaccuracy in analog thermometers, but digital? Should be dead on, right? One of the meters is a hygrometer and I can't really be assured of an accurate relative humidity reading either.

-Boofer-

[DeejayDebi]

Sorry Dave I should have brought this up. This has been a major plague to us meat smokers for years. The first thing we tell every newbie is to calibrate your thermometer!

I thought I had stated that a few times when people where having apparent temperature issues. . It's one of the reasons I prefer Taylor thermometers they are easy to calibrate. The tiny nut on the back threaded into the bezel is used to fine tune the thermometer.

The key calibration is knowing where you are because we use boiling water as one of the tests and water boils at different temperature depending on altitude. Water boils at lower temperatures with every 1,000 feet of altitude.


Calibrating a thermometer Procedure At Sea Level:

Cold Procedure:

Fill a cup full of ice and then fill with water. Wait a minute for the temperature to stabilize. Stick the thermometer into the ice water.

Your thermometer should read 32°F or 0°C if not adjust as needed.

Hot procedure:

Place distilled water in a pot and bring it to a rolling boil. Check the temperature. It should be 212°F or 100°C


What you have found seems to be the norm and not the exception to the rule these days.


Here is the procedure and table for altitude adjustments:

http://www.deejayssmokepit.net/Downloads_files/CalibratingThermometers.pdf

[Alex]

I've had very inconsistent results with the three digital thermometers I have. I might have expected inherent inaccuracy in analog thermometers, but digital? Should be dead on, right? One of the meters is a hygrometer and I can't really be assured of an accurate relative humidity reading either.

-Boofer-

There is a very simple method of checking your humidity meter.

Calibrating your hygrometer:
First check to see if your hygrometer can be adjusted. Look at the back to see if the small center post has a slot for a small screwdriver. If it does you'll need to have a screwdriver ready to make any adjustments as soon as you open the jar. If it doesn't, don't worry, this procedure will still allow you to use your hygrometer more effectively.

Half-fill a shot-glass or other small dish with table salt and add enough water to wet the salt completely but not dissolve it--it should be like wet sand. Put the shot-glass and hygrometer in a wide-mouth jar, and seal it airtight. After six hours (or more), the humidity in the jar is 75%. The hygrometer should read somewhere around 75%. If it does not, take the screwdriver and turn the screw on the back of the hygrometer until the meter reads 75%.

If your hygrometer is non-adjustable and reads other than 75% in the jar, you must correct all subsequent readings by this difference. Example: if the hygrometer reads 67% in the jar, it is reading 8% low. Thus, it will always read 8% less than the actual RH. Using this example if you wanted the humidity to be 60-70% then the reading on your hygrometer would have to be 52-62%.

[Likesspace]

Debi....
You're my favorite!
I was ready to pitch my large dial analog thermometer, and in fact would have if not for deciding to save it to pierce Stilton styles cheeses. I had no idea that it could be calibrated!
Well after reading your post I looked at the back and sure enough, there was the nut you talked about.
This thermometer is not a Taylor brand in fact it came in a sealed plastic bag with NO instructions or directions. Because of that I just assumed that it was ready for use and never gave it another thought.
I bought this from New England Cheese Making Supply and it really ticks me off that there were no instructions concerning the need to calibrate. If you were in the cheese making supply business, wouldn't you think that this was valuable information?
Well anyway, I just finished doing the calibration and I now have three thermometers that are within 1/2 of a degree of one another which makes me happy. Now I'm thinking I can finally start making the cheese that I've been after for the past three years.
I do think I'll have to start cutting back on my rennet now that my temps are right. I just did the spinning bowl method on a batch of cheddar and had floc within 6 minutes. I have NEVER seen that happen before.
Thanks again for the information Debi. A cheese for you.

Dave

[DeejayDebi]

Sorry you had to go through the frustration of all this before I thought to post the info. Sometimes I get confused about what I posted here or at my place or where the heck I put something at all. CRS!

I guess the point we should tell the newbies is to look for that nut! They don't all come that way anymore. I see many at stores that are just disposable I guess.

Many of the digital are not calibratable at home and that stinks. Even for a simple dinner 10 degrees could be the difference between a great meal and ecoli. I have written to the FDA to complain that warnings should be placed on thermometers but the claim its up to the buyer to know - kind of buyer beware thing. Sheesh!

[Likesspace]

Well Debi, in my opinion the FDA have proven that they are idiots. I mean if there is no documentation with the thermometer, how are we in the general public to know that calibration is even needed??
Even though I'm a guy, I'm the type that does read the owner's manual of EVERYTHING that I purchase. I don't care if I buy a new ink pen, if it comes with a manual I'll give it at least a quick "once over".
I'm still really ticked about this, especially since I purchased this from a well known and well respected cheese making supply store.
The good news is that today I got the best curd set I've ever seen and realize that I am now going to have to adjust my ingredient amounts to a lower level. Other than all of the milk that I've probably wasted, this is good news for me. I'm sure I will now be using considerably less of both culture and rennet which makes me happy that I also sprang for a new gram scale earlier in the week.
Thanks again for your help Debi. I really do appreciate it.

Dave

[DeejayDebi]

You most welcome Dave. That's what I am here for!

[Boofer]

Thanks, Alex.  Why wouldn't the RH go to the 90s? Why only 75%?

My new La Crosse thermometer/hygrometer is not adjustable. I'm trying your experiment. I'll know I guess after 6 hours.

-Boofer-

[Alex]

That's a text I've found on the net recently.
I clibrated mine by laying a very wet piece of kitchen towel or anything similar on the sensing opening of the meter for the same hours. In this case, the final reading should be 100. If not, act like previously described.

[Boofer]

Okay, Alex, I followed your guidance. The hygrometer has been in the sealed tub overnight with the small container of salt and water. The reading is 65.4F/73%RH. I checked a couple times before I went to bed and it was pretty much sitting around the 74% mark. I have found that it adjusts slightly with the temperature.

Over the past several weeks I have been doing other small tests with my newly acquired La Crosse thermometer/hygrometer. I had a sensor sitting outside in the rain (the sensor has a rain cover) and it may have gotten up to 94%RH, but certainly nowhere close to 100%. How can that be? Isn't rain close to 100%? Maybe if it was sitting in a greenhouse or somewhere where orchids are grown...? Hmmm. I think the wisdom is seeping in now. Ah, yes, there it is!

Do you have a link to that text that you referenced?

Anyway, what I have decided I need is to approach the climactic conditions of a cool orchid house. My cave actually seems to do that quite well. Every so often when the right cheeses and the right ambient conditions exist outside the cave, I need to wipe down the walls to clear the moisture. Not all the time. With winter conditions settling in, the ambient air will be drier and so the cave will not be as moist. I may need to implement the soaking cheesecloth "wick" in front of the fans.

The Manchego I did yesterday is in its plastic minicave sitting at 66F/75%. Seems about right. Outside, the weather has been blowing (up to gale-force winds last night) and currently sits at 26.6F/24%. It's going to be a COLD winter.

-Boofer-