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  1. #21
    wogster's Avatar
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    What is typically called a fever thermometer, they should be quite accurate from about 35-40C. If your temperature is above or below that range, it doesn't matter, because you need to immediately go to a hospital for medical attention. They can be a little slow to get a reading though....
    Paul Schmidt
    See my Blog at http://clickandspin.blogspot.com

    The greatest advance in photography in the last 100 years is not digital, it's odourless stop bath....

  2. #22
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    Oh, I find they are pretty quick. Of course, a minute or two is recommended when reading your body temperature, but this is because the contact to skin may not be perfect. But stir it in a liquid - it takes just about 15 seconds or less. It comes down to the heat capacity of the sensor/meter which is fairly directly related to the mass of the device.

    The "resetable by shaking" maximum reading feature in some mercury meters might get a little bit irritating, though...

  3. #23
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    Quote Originally Posted by hrst View Post
    There is one type of a cheap "household" thermometer that meters just perfectly at 100F/37.8C,
    Good for color but not so much for B&W. I could keep my old one for that, I suppose.

  4. #24
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    Although I have a mercury thermometer bought in a chemical laboratory equipment shop and an electronic "fever" thermometer, I notice that, in fact, I don't measure temperature at all. Using a CPP-2 with built-in thermostat, I leave the chemicals in the machine while it warms up and I let it warm up (at 38.3 °C) for more than half an hour so that all elements (all plastics, all flasks, the tank etc.) are more or less at the same temperature, around 38.3.
    Using always the same temperature on the Jobo and having basically around 25° in the bathroom I obtain consistent results, so I stopped worrying about the exact temperature, consistency is more important than temperature precision, if you time your baths exactly.

    The infrared beam model seams to me the best choice if and when I decide that I need one. My sister bought one to check temperature on her baby and it's spectacular, no contact with chemicals so no risk of cross-contamination if you want to check more than one bath (although the really critical one for temperature is only the developer).
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
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  5. #25
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    I use an old Ilford mercury thermometer (with an F scale), which I have calibrated against a thermometer my wife bought when we started trying to have kids (apparently, these were supposed to be super accurate to check when a woman is ovulating, or so it goes).

  6. #26
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    I agree wit Diapositivo, with a Jobo, you don't need to take any measurements (well, maybe except for control measurements from the water bath every few months), but it takes a surprisingly long time for the developer to reach the water bath temperature to the tolerance of +/-0.2C. I agree it's about half an hour. That's why I'm metering the developer and giving it brief baths in really hot water to bring it up to temp in just a few minutes. (Do this carefully: you need to have the liquid in the bottle in motion by stirring it, and measure once again after 30-60 seconds you have placed it back in Jobo.)

  7. #27

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    I can heartily recommend the following: Thermoworks RT301WA:

    http://www.thermoworks.com/products/...t/rt301wa.html

    I like it because it can be easily calibrated. If you know your local air pressure (easy to get) and can boil distilled water, you can calibrate the thermometer so it reads the proper temperature at your location - in my case it was 100.2C

    On the other side, you freeze some distilled water, then make a slush with a combination of crushed ice and distilled water. Stick your thermometer in, and calibrate it so it reads 0.0C. That's it. I tested this thermometer against 3 lab-grade devices, and it was bang-on accurate.

  8. #28

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    I use a Paterson Colour Thermometer (was $27 at Calumet) and then determine the corresponding temperatures on a digital thermometer (LCD with probe) that is actually used during developing (for b&w, 68F on the color thermometer = 69.1F on the digital). I do the calibration occassionally as the digital thermometer might change as the battery depletes. This has worked well for both color and b&w developing.

  9. #29
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    Quote Originally Posted by Arkasha View Post
    I can heartily recommend the following: Thermoworks RT301WA:

    http://www.thermoworks.com/products/...t/rt301wa.html

    I like it because it can be easily calibrated. If you know your local air pressure (easy to get) and can boil distilled water, you can calibrate the thermometer so it reads the proper temperature at your location - in my case it was 100.2C

    On the other side, you freeze some distilled water, then make a slush with a combination of crushed ice and distilled water. Stick your thermometer in, and calibrate it so it reads 0.0C. That's it. I tested this thermometer against 3 lab-grade devices, and it was bang-on accurate.
    You know, we really don't need it to be that accurate, as long as it's consistent in it's error. Most mercury and spirit thermometers are, it may read 38C and actually be 37C or 39C, but it will have the same error from the factory until it gets dropped. This means that your work flow will adapt to the thermometer. The problem is that electronic ones can drift, as they age, when it says 38C, it could actually be 37.9C and a couple of years later actually be closer to 36C..... The battery power level can also affect this. I don't know about the dial type, last time I saw one being used for photography it was B&W and with black and white, you can be off as much as 2-3C and it doesn't really matter.
    Paul Schmidt
    See my Blog at http://clickandspin.blogspot.com

    The greatest advance in photography in the last 100 years is not digital, it's odourless stop bath....

  10. #30

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    wogster,

    You can recalibrate this thermometer, to account for drift. It's also quite inexpensive - about $25 delivered.

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