I am looking for an accurate thermometer (non-glass). I've used the Kodak SS ones and they are not as accurate as I am looking for. Digital is okay. thanks for any recommendations. carol

-- carol maurin (cbmaurin@earthlink.net), November 12, 2000

Answers

Accurate digital thermometers are available from chemical supply houses for less than $20. However, just because the temperature of the developer is EXACTLY 68F doesn't mean it's going to STAY that temperature for very long, especially if you are developing sheet film in trays where your hands will continually warm up the solution. Or where the ambient temperature is more than a couple of degrees away from 68F. You may want to consider the Zone VI compensating developing timer. This unit reads the time as if the solution is 68F, no matter what the actual temperature is. Good luck.

-- Michael D Fraser (mdfraser@earthlink.net), November 12, 2000.

I did some quick research on this topic a while back and was dismayed to find that thermometer manufacturers don't have much to say about accuracy. Even though you buy something with great resolution, it may or may not have good absolute accuracy. I don't want to use a glass (esp. mercury) thermometer in the darkroom, but I keep a good one stored away as my reference to check all my other ones. Some claim that absolute accuracy isn't necessary- I disagree. Let's say you have a perfectly functioning zone system, but your thermometer is 3 degrees off and you don't know it. You break it. Goodbye perfectly functioning zone system until you recalibrate. If you know your errors, you just get another thermometer, calibrate it, and it's business as usual. Just an example- zone isn't my thing, but measurements are. BTW, check out Fisher Scientific- model 15-000A for about $23.50 (last year). It's -1 to 51 degrees C with 0.1 degree resolution. Glass- use only as a reference tool.

-- Conrad Hoffman (choffman@rpa.net), November 12, 2000.

I checked a cheapo stainless steel probe digital thermometer (UK equivalent of $8US, bought at a market stall) against a calibrated glass-mercury thermometer. They were in total agreement. Worrying about fractions of a degree is verging on paranoia, especially as most glass thermometers can't be read that accurately.
Unless it's fallen out of a Christmas cracker, any thermometer should be accurate to less than 3 degrees, except, of course, those bi-metal dial type abominations.

-- Pete Andrews (p.l.andrews@bham.ac.uk), November 13, 2000.

Be careful, most digital thermometers (GOOD ones) are only accurate to +/- 0.3%, percent NOT degrees. And these are NOT the under $20 ones. Many of the cheaper ones are accurate to less than 3%.

There are two things, absolute accuracy and repeatability. Absolute accuracy is what you check when comparing it to a high quality glass thermometer. But if it isn't repeatable, everytime you use it, it will give you a difference answer.

The BEST is the Kodak Process Thermometer. It is glass, but in a SS sleeve to protect it very well.

I looked at digital, including high end (over $300) ones, and they just aren't there.

-- Terry Carraway (TCarraway@compuserve.com), November 13, 2000.

Can I just add that even a calibrated liquid/glass thermometer won't be accurate unless it's used properly. Some have an immersion line engraved on them, and this type is only accurate at one specified air temperature.
If there is no immersion line, then the entire mercury or spirit column should be in the liquid to get the correct reading. Not terribly convenient in a deep tank!
My mercury certified thermometer gives 1/2 deg F variation between simply dipping the bulb and fully immersed.

-- Pete Andrews (p.l.andrews@bham.ac.uk), November 14, 2000.