Horace Heffner <[email protected]> wrote:
> This is from page 4 from my review: > > "This photo by Mats Lewan of NyTeknik of the 6 Oct Rossi Tout thermocouple > . . . Thank you! I knew I saw that somewhere. Since Lewan took that photo I think I will copy it to RossiData. It was thus subject to the air temperature in the volume underneath the > insulation and between the > brass manifold and steel nut. My tests indicate that air temperature of trapped air is not a problem. That is to say: When your goal is to measure temperature to the nearest 0.1°C, trapped air will not affect the result. If you are trying to measure smaller temperature differences the way McKubre or Storms does this might be a problem. Exposure to ambient air will cause a problem. > It is especially notable that the frayed insulation, cut from around > the probe tip, was not trimmed. This is very unusual. No, it isn't. The thermocouples I have purchased from Omega all came looking like this. I can upload a photo if you would like. > The frayed electrical insulation may have prevented > good thermal contact of the thermocouple with the steel nut . . . Not a problem. It is well clear of the nut, and even when the end of the thermocouple is kind of messy with cotton from a Band-Aid it still works perfectly okay. I discovered. *Again let me emphasize*, I'm talking about when you are trying to measure to the nearest 0.1°C. Not a precision measurement. The kinds of issues you cite would be a problem with a precision laboratory grade calorimeter, but for the measurement of this type these issues will not have a measurable effect. If you doubt that, I suggest you try using a thermocouple in a variety of situations, with liquid, metal, roast turkey, etc. - Jed
