Food Thermometers

chowhound

chowhound

New member
I recently tested my thermometers in boiling water and just one, the candy thermometer I use in the lid of my smoker, was off just a little. I moved the red slide arrow to indicate where I thought 225 would be, counting the 9 degree error.

Problem 1: Yesterday my smoker took a small temp dip, down to 190. I restoked the coals and my digital probe seemed to read correctly, indicating a rise in temps to where I wanted to be, but the lid thermometer never came back up... I'm not sure if these analog type thermometers need to completely cool before registering correct temps again? You wouldn't think so.

Problem 2: This morning my one of my probes was still in the smoker. The other one was brought in with the meat last night. The probe still in the smoker indicated 64F. If it was over 40 this morning I would be surprised. Frost was everywhere. And I checked the smoker I had choked out last night and it was stone cold.

These were thermometers I had just checked out a few weeks ago. I don't get it. I have no idea which ones are correct or broken. I suppose I could check them again, but I have a feeling 212F in boiling water is going to show everything is hunky dory again.

Do, or can, thermomters go bad and read correctly for one temp, but not another? And the digital probes... can those suddenly lose the ability to read correctly throughout their range?

I suppose I could just buy new ones, but that seems kinda stupid if there's something else I can do to see if these are indeed working correctly. They certainly seemed to be working correctly for the bulk of yesterday's cook.

Any advice or like situations? Are thermometers considered expendible cooking tools, needing replaced regularly whether you think they are working or not?
 
Funny you mention this Chow. When heating up my smoker I left the probe just hanging inside so as to tell when it was up to 250 or above. My meat thermometer did fine up to 199 and never went any higher. I've seen a reading as low as 60 degrees and never paid it any mind after that. I suspect your digital has a low reading of 40 and won't go any lower. I'm a good ways south of you and we saw 25 degrees F for our outside temps this morning. I expect your temps were similar. I suspect these things are not meant to tell a whole range of temps ....just in the range of what they were designed for.
 
That could be a strong possibility.

Another thing with the digital probe... when I took it outside yesterday, one probe read something like 65 and the other 52, then they both worked towards each other until they read the same. I've never seen that before. Usually they read the same when I plug them in and turn it on. Maybe I'll check the batteries just in case.
 
Yes, thermometers are designed for a certain range. Even though the guage may say otherwise, you may get false readings in a lower or higher part of the range.
 
chowhound said:
I recently tested my thermometers in boiling water and just one, the candy thermometer I use in the lid of my smoker, was off just a little. I moved the red slide arrow to indicate where I thought 225 would be, counting the 9 degree error.

Problem 1: Yesterday my smoker took a small temp dip, down to 190. I restoked the coals and my digital probe seemed to read correctly, indicating a rise in temps to where I wanted to be, but the lid thermometer never came back up... I'm not sure if these analog type thermometers need to completely cool before registering correct temps again? You wouldn't think so.

Problem 2: This morning my one of my probes was still in the smoker. The other one was brought in with the meat last night. The probe still in the smoker indicated 64F. If it was over 40 this morning I would be surprised. Frost was everywhere. And I checked the smoker I had choked out last night and it was stone cold.

These were thermometers I had just checked out a few weeks ago. I don't get it. I have no idea which ones are correct or broken. I suppose I could check them again, but I have a feeling 212F in boiling water is going to show everything is hunky dory again.

Do, or can, thermomters go bad and read correctly for one temp, but not another? And the digital probes... can those suddenly lose the ability to read correctly throughout their range?

I suppose I could just buy new ones, but that seems kinda stupid if there's something else I can do to see if these are indeed working correctly. They certainly seemed to be working correctly for the bulk of yesterday's cook.

Any advice or like situations? Are thermometers considered expendible cooking tools, needing replaced regularly whether you think they are working or not?
Click to expand...



I tested all of mine not too long ago, and they all seem fine. :chef:
 
I checked my batteries in the digital thermometer and they are fine. Yet it was reading 88F yesterday on a day that it may have gotten up to sixty... And I stuck the other probe on and that was five degrees different. I think something must have happened to it or something. I seem to remember it reading correct even at room or outside temps. Maybe I'll give the manufacturer a call today if I can locate their number.
 
chowhound said:
I checked my batteries in the digital thermometer and they are fine. Yet it was reading 88F yesterday on a day that it may have gotten up to sixty... And I stuck the other probe on and that was five degrees different. I think something must have happened to it or something. I seem to remember it reading correct even at room or outside temps. Maybe I'll give the manufacturer a call today if I can locate their number.
Click to expand...
Check to see if they have a website that may contain FAQs.
 
I tried two different analog thermometers in my smoker. Both tested ok in boiling water, but they were all over the place when I used them for smoking. I don't even look at them now. Just use the digital...
 
I found a quirk that my digital thermometer at work. It has an "auto-shut-off" feature, to conserve battery life.

Well, apparently the shut off feature is damaged, or doesn't work like it should. If the thermometer is left on long enough, it will lock at whatever temperature it is registering at that time. It won't turn off, or back on. The only way to get the probe to work again is to remove the battery for a few minutes, then put the battery back in.

I calibrate this thermometer every few weeks, and it usually registers within a degree or two of 32 degrees F in the ice-water test.

Have you all with the analog thermometers tried doing BOTH a boil test and an ice water test? It could be that the spring that controls the needle contracts/expands beyond specifications, resulting in a false reading.
 
Wouldn't it be better to calibrate using boiling water since it's more towards a working range? Unles you're using it for Chardonnay. lol
 
I have always had a question about checking thermometers in water being it boiling or ice. How do you know exactly what temperature the water is when you test it. I know water freezes at 32 deg. F and water boils at 212 deg F but..... Water can still be frozen a couple of degrees higher since it hasn't melted yet as well as boiling can be much higher as well. The point being I use two thermometers one a medical type in water then compare it to the cooking type.
 
When I measure the temp of boiling water the temp does not go up as a function of time once the boiling starts. Lots of small chunks of ice in very little water in a container set in room temperature air is going to produce a water temp extremely close to 32F.
 
buzzard767 said:
When I measure the temp of boiling water the temp does not go up as a function of time once the boiling starts. Lots of small chunks of ice in very little water in a container set in room temperature air is going to produce a water temp extremely close to 32F.
Click to expand...

True that is :agree:
I Googled how to check thermometers when I did mine and this appears to be the most accurate way to check them.
 
Not only that, but depending on your air pressure, water will boil at a lower temperature than 212 degrees F. Heck, if you put a bowl of water into a vacuum chamber, and start pumping out the air, two things happen:

1) Due to the Laws of Refrigeration, as the pressure goes down, the temperature goes down as well.
2) Once the air pressure in the chamber meets the valence pressure (?) of the liquid, the liquid will literally begin to boil (at room temp).

In fact, if you keep pumping out the air, the temperature will continue to drop, until it reaches, then drops below, 32 degrees F. Freezing point of water is NOT affected by air pressure. You can quite literally freeze water while it's boiling, if the air pressure is low enough.

Personally, I like the idea of checking thermometers with the boil test. However, my digital that I use as work can only be calibrated with ice water. It was designed that way, probably to get around changes in the boiling point due to air pressure.
 
That is because of Colorado's high elevation level, and the fact that they get very early winter and late spring seasons.

Water IS supposed to be at 212 degrees when the boiling point is reached. If the water is in a preasure cooker, then the boiling point is riased from 212 to about 280 or so degrees.
 
Other things can also raise the boiling point of water such as minerals/salts in the water. This would be the case of comparing the boiling point of hard water and soft water. This can be tested easily when you make pasta, bring the water to a boil then add salt then let it come back to a boil before adding the pasta.
 
Yeah, I noticed that adding salt to the water just before it reaches the boiling point briefly clouds the water and seems to make it hotter.
 
Salt raises the boiling point of water as will oil both of which have the same effect as hard water would in really bad cases.
 
the boiling point only depends on the actual barometric pressure.

if you've got a barometer, that works fine. but 'as seen on TV' numbers are not necessarily 'accurate/real' - see:

http://www.virtualweberbullet.com/boilingpoint.html

pursuing the technicalities, it is not possible to simultaneously freeze and boil water by reducing "atmospheric" or the pressure to which the water is exposed.

at exactly the freezing point - temperature wise - water can exist in two states - as a solid (ice) or a liquid (really cold water)

if a pot of water is subjected to decreasing absolute pressure, it will boil. artificial means are then required to lower the water temperature to less than boiling. that stops the 'boiling' but does not stop 'evaporation' - which is a surface effect. an absolute vacuum cannot be achieved - as soon as a single molecule of water has evaporated the absolute vacuum is no longer absolute. further attempts to maintain an absolute vacuum at the freezing point will result in the water evaporating before it freezes. driven to the end point, there's an empty pot - which used to contain 32'F water - and a perfect vacuum - no atoms or molecules of anything present in 'the vacuum'
 
You must log in or register to reply here.
Top