Hi,
I would like to purchase a classic thermometer (Hg) with 0.1°C resolution to compare the readings with my DVP2. I was browsing the internet a little but did not find any store that has these items for sale.
Any recommendation?
Thanks.
In UK private individuals are not allowed to buy mercury thermometers, maybe the same applies elsewhere?
Apparently a combination of indium, gallium and tin is now used. I didn’t know that!
I’d be surprised if you can get a glass thermometer covering a wide enough range with 0.1C markings. You’d probably need -20C to +50C so with just 1mm for each 0.1C you’re looking at a thermometer that would be 750mm long.
Mercury in thermometers is not allowed in our country as well. My expression was not really OK (not a native English speaker 
)Actually I’m interested to get a classic thermometer which doesn’t require calibration over time so I can compare the readings to my other (digital) sensors. (Old) meteorological weather stations use min/max thermometer types which are monitored by observers (human) and they report the readings at specified periods.
My DVP2 is 7 years old and after last year’s heatwave, I lost trust in the max readings. That is why I’m looking for an alternative which I can trust.
I don’t think you’ll find one with a wide enough range graduated to 0.1 degree intervals.
I had a quick look at the Fisher Scientific web site as they’re one of the big suppliers of this kind of equipment and whilst they do offer some glass thermometers with 0.1C markings they are for smaller ranges than you’re likely to see in your annual readings. If you want to cover the normal meteorological temperature ranges then I think you’re probably going to be limited to 0.5C markings.
Having said that, does a temperature difference of +/- 0.1C mean anything in the real world. It can be measured but does it actually change anything if it’s 25.2C or 25.3C or even 25.0/25.5C with 0.5 degree markings?
Even if the thermometer is certified correct when you buy it, classic glass thermometers require calibration over time.
One wire (1-wire) temperature sensors are guaranteed to be within 0.5 degrees so are likely to be even better than that and only cost a few dollars. Some types may even have closer tolerances. On top of that Raspberry Pi computers have a native one wire interface. Other than that you can buy USB interfaces that are reasonably priced to use on a PC for instance. Free software is available to read the sensors which would be all you need for calibration purposes.
Ian