How awful are dial thermometers?

The answer is "even worse than I imagined"!

My BP rescue came with a viv, complete with a dial thermometer and hygrometer. I knew they were pants already so I had two proper digital thermo/hygrometers available from the start. For the record, the dial thermometer overred by 12°C/20°F, and the hygrometer underred by 45% (!!) with the digital probes were stuck on the front glass of the dials for comparison.

During my monthly clean today, I finally decided to get rid of this nonsense.

Breaking them open, I found the expected coil of bimetallic (?) metal in the thermometer. The hygrometer had the same sort of thing, but one side of the coil has paper adhered to it, presumably to absorb moisture from the air.

What DID surprise me - the coil/needle pivots were simply attached through a hole in the cardboard dial and were not attached to the plastic backing - and are free for the pivot to rotate in the card. Indeed - a sharp shock perpendicular to the needle would cause the apparent reading to permanently change by a few degrees since the pivot rotates in the card.

I guess this is a rambling way of saying: Every warning against these things is justified and then some, and I can't see how they're even suitable as a guide. They're worse than useless.

https://dl.dropboxusercontent.com/u/...ial_Therm2.jpg

Those read ambient temperature which isn't as important as surface. :rofl:

Yeah they're probably OK for general temp readings in an office or wherever ...

I've ranted on this before, and yeah, the pet trade dials suck, but in my experience, many of the digitals are junk too. I have three relatively new Vivarium Electronics therm/hygros, and two of them don't work at all, and the third seems to spontaneously switch from F to C all on its own, even out on my desk. (Waste of money, and because of that my next t-stat, will NOT be a VE. No trust in that brand anymore.)

A search can yield some dials that appear to be better quality than the Exo's and Zoo meds (why do those companies even attatch their names to this stuff?), but I've not actually purchased any yet. The only thermometer reading I actually trust is off the lazer thermometer.

You can't really get a dial thermometer to measure where it matters and anything "made for" the reptile trade is garbage. There are very accurate dial thermometers, but honestly kinda useless for us keepers anyway.

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Originally Posted by distaff

I've ranted on this before, and yeah, the pet trade dials suck, but in my experience, many of the digitals are junk too. I have three relatively new Vivarium Electronics therm/hygros, and two of them don't work at all, and the third seems to spontaneously switch from F to C all on its own, even out on my desk. (Waste of money, and because of that my next t-stat, will NOT be a VE. No trust in that brand anymore.)

A search can yield some dials that appear to be better quality than the Exo's and Zoo meds (why do those companies even attatch their names to this stuff?), but I've not actually purchased any yet. The only thermometer reading I actually trust is off the lazer thermometer.

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Quote:

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Originally Posted by OhhWatALoser

You can't really get a dial thermometer to measure where it matters and anything "made for" the reptile trade is garbage. There are very accurate dial thermometers, but honestly kinda useless for us keepers anyway.

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^This! You can get very accurate Dial or Digital instruments, but it is going to cost you. Anything that is sold as "reptile/animal specific" is generally mass produced and not the most accurate, best bang for the buck as far as accuracy would be a nice IR temp gun.

Sounds like infrared thermometers is the way to go. Is there a good alt. option for keeping track of humidity?

For humidity you will just need to find an accurate gauge. Generally weather gauges are pretty accurate, some even come with a calibration cert. I have had pretty good luck with equipment from ambient weather. I have compared their readings against gauges in my calibration lab and they so far have stayed dead on.

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I put my dial thermometer in the fridge. (I got it with a setup thing for the burm. I dont use it though)
Before it read about 25*C, and after I put it in the fridge overnight (which is set at 4*C), the dial read 10*C.

It shows how unreliable these things can be. I use a temp gun and some nice thermometer/hydrometers from SwellUk.