# Longevity/accuracy of digital thermometers?



## bluewhisper (Jul 25, 2014)

I have acquired three digital thermometers over the years. I became suspicious of their accuracy, so I gathered them all together and let them rest with their probes all in the same place.













digital_deviation.jpg



__ bluewhisper
__ Jul 25, 2014






Here's an Oneida showing 72, a Pyrex showing 68, and a Farberware showing 66.9. Before this test I polished the probes and jacks with steel wool.

Are these like digital cameras that are expected to crap out over time? How long are they expected to last? Is there any way to tweak them to a correct reading, like zeroing a scale? Could this simply be a battery power level issue?


----------



## ryan in louisville (Jul 25, 2014)

It's not necessarily age that has caused them to be different.  Could very well be tolerances of components inside that make the measurements.  Try the ice bath test and see what they read.  You can also put them in boiling water and record the variation from 212F and use them knowing there is a variation.

You mentioned you cleaned the probes with steel wool.  I would suggest you thoroughly reclean them with something tto get rid of the steel residue.  Steel residue leads to rust, which can lead to tetanus.  Passivation is the cleaning of stainless.  Here is a page that briefly talks about passivation at home.  You might try oxyclean (that Billy Mays promoted) and scrub with a stainless pot scrubber.

http://www.howtobrew.com/appendices/appendixB-1.html


----------



## noboundaries (Jul 25, 2014)

Digital therms are slaves to their software.  Having three different manufacturers can complicate things for you.  Understand that and you'll know what they are telling you.  I've not heard of a way to tweak their accuracy other than doing the mental math after doing a boil test.  Maverick says that a 3-4 degree temp difference on the boiling water test is acceptable error.

I have a cheap digital $10 quick read, two Mavericks (ET-732 and an older non-wireless single probe OT3-BBQ), plus I have the BBQ Guru DigiQ DX2.  All give me different readings but it appears to be an algorithm issue more so than a mechanical response.  

The cheap digital quick read gets used when oven cooking and it works fine for food temp. I've had it for heck, ten years.  Never changed the battery.  When it craps out I'll just buy a new one. 

I use the OT3-BBQ in my gas grill, which doesn't get much use these days.  I've had the OT3-BBQ for several years.  I used all the fancy features, including alarms, initially.  Went through a set of batteries in 3 months.  I stopped using the fancy features, especially the alarms, and just use it for chamber temp. I haven't changed the batteries in at least three years. 

I use both the Guru and the ET-732 together in my smoker.   The sensitivity is greatest on the Maverick and I can see chamber temp change just from shadows on my smoker or the wind picking up.  The Guru has much more of an averaging algorithm and I don't see it change much once it reaches the desired chamber temp.  Both will eventually read the same chamber temp but the Maverick fluctuates more. 

I don't use the food probe on the DigiQ DX2.  It passed the boiling test just fine but it reads several degrees off from the ET-732.  I trust the 732 for telling me the correct temp on the meat.  The first time I used the DigiQ DX2 I used its food probe temp as a guide to see what I'd get.  The ET-732 was telling me 140F on a beef roast.  The DigiQ was saying 135F, my target temp.  The ET-732 was correct based on the over-doneness of the meat.   

I don't bother with any of the fancy features on any of the therms any more. All I want to know is chamber temp and food temp, and I know what to trust and how to use them.


----------



## bluewhisper (Jul 25, 2014)

*sigh* I added a refrigerator thermometer and an analog probe cooking thermometer, and they don't agree with any of the digitals, though they're within the same range.


----------



## dr k (Jul 25, 2014)

Noboundaries said:


> Digital therms are slaves to their software.  Having three different manufacturers can complicate things for you.  Understand that and you'll know what they are telling you.  I've not heard of a way to tweak their accuracy other than doing the mental math after doing a boil test.  Maverick says that a 3-4 degree temp difference on the boiling water test is acceptable error.
> 
> I have a cheap digital $10 quick read, two Mavericks (ET-732 and an older non-wireless single probe OT3-BBQ), plus I have the BBQ Guru DigiQ DX2.  All give me different readings but it appears to be an algorithm issue more so than a mechanical response.
> 
> ...


I have the Maverick OT3-BBQ therm as well and it is a great cooking chamber only therm.


----------



## dr k (Jul 25, 2014)

RYAN IN LOUISVILLE said:


> It's not necessarily age that has caused them to be different. Could very well be tolerances of components inside that make the measurements. Try the ice bath test and see what they read. You can also put them in boiling water and record the variation from 212F and use them knowing there is a variation.
> 
> You mentioned you cleaned the probes with steel wool. I would suggest you thoroughly reclean them with something tto get rid of the steel residue. Steel residue leads to rust, which can lead to tetanus. Passivation is the cleaning of stainless. Here is a page that briefly talks about passivation at home. You might try oxyclean (that Billy Mays promoted) and scrub with a stainless pot scrubber.
> 
> http://www.howtobrew.com/appendices/appendixB-1.html


Looks like I'm going back to one of those green non metallic scrub pads.  I was using steel wool to.  I've noticed that stainless steel hardware has been rusting like license plate bolts I installed with new plates.  It must not have much chromium in them and they haven't been touched for 3+ years.


----------

