The lost formula - Printable Version +- HP Forums (https://archived.hpcalc.org/museumforum) +-- Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum-1.html) +--- Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum-2.html) +--- Thread: The lost formula (/thread-177122.html) The lost formula - designnut - 01-16-2011 I thought the knowledge that this ccould be done migtht inspire someone to find it again. The formula for the resisttance of negative temperature coeffient thermistors. is agonizingly ccomplex and works in a limited range. When I bought my HP65 I was working with thermistors and tried to match the resistance temperature curve by trying various things. I used only 3 constants for the particular one I was trying to match. The part I recall is adding a large number (~1200) to the temperature in C and taking ln. I used one constant to fit the resistance of that particular size device. It was dirt simple and truly accurate over the full range. I looked in my books for marginal references to what I had done and found none. I thought the knowledge that itt had been done might stimulate others to find it. sam Re: The lost formula - Garth Wilson - 01-16-2011 I'm sure it's on the manufacturers' websites. Re: The lost formula - Dan W - 01-16-2011 Are you talking about the Steinhart-Hart equation? Re: The lost formula - John B. Smitherman - 01-16-2011 A bit of wikipedia: Thermistors Regards, John Re: The lost formula - designnut - 01-17-2011 On reading something everyone impress it on the matrix of "what they know". There can be nothing new under the sun, everything that can be learned has always been learned. You miss a lot of information that way. The impact of what I wrote is that there is a simple accurate method not disclosed by usual methods. Read the message with an open mind, your brains won't fall out. Sam Re: The lost formula - Walter B - 01-17-2011 Sam, things which have been (very) tedious in the past may be far easier nowadays and become even easier in the future, caused by new insight or just compilations of older insights. This process goes on and on. As a famous scientist once said: "We are standing on the shoulders of giants." HTH, Walter Edited: 17 Jan 2011, 2:09 a.m.