Quote Originally Posted by jeffeb
I recently acquired a Paterson darkroom thermometer and I was using it to monitor the temperature of the water in my Jobo CPE. However, I started to have my suspicions about the accuracy of the thermometer when I had to turn up the temperature on the Jobo in order to obtain the desired 24 degrees C. I dug out my Jessops thermometer and I was amazed to find that it had an indicated reading of 26 degrees C. I would expect half a degree difference between the thermometers but two degrees, thatís a lot. I then had to dig out a brewing thermometer to see if I had two thermometers that agreed. The brewing thermometer concurred with the Jessops thermometer.


I now find myself in the market for a decent thermometer. My priorities are reliability, consistency and long life. Reasonable accuracy would also be helpful

Iím thinking of getting a digital thermometer as Iíve managed to break the glass type in the past. Does anyone have any experience of the Kaiser or Ilford digital thermometers? The Ilford model is almost three times the price of the Kaiser thermometer. Is it worth it? Whatís everyone else using out there?


Brian
Brian,

If your liquid-in-glass (LIG) thermometer is not calibrated or certified (to NIST or ASTM), then you cannot know its accuracy. Because you do not know its accuracy, how do you know which one is reading correctly? Hypothetically, if your thermometers were only accurate to +/-1 deg C, then a difference of 2 deg C would still be within specification, because (24+1)=(26-1).

Your scale divisions will most likely be every 0.5 degrees (or 0.2 or 1.0). This scale solely determines the thermometer's resolution, not its accuracy.

Your thermometer will also be the partial immersion type which is inherently less accurate than a full immersion type.

Other folks have suggested purchasing the RH Designs digital thermometer http://www.rhdesigns.co.uk/darkroom/...ermometer.html. I can't see what the advantage of this is, because its quoted accuracy is still only
+/-1 degC over the temp. range of darkroom chemicals.

regards
Peter