Oznog
Active Member
I have a spec for a water temp gauge that uses an NTC thermistor. The mfg also provided a chart of resistance vs temp.
But, there's something weird here. I use the std formula for calculating the device's B constant from any two R-T points and I get very significant difference in the B-constant depending on whether I take it from high temp points or low temp points. Like 3600 at low temps and 4000+ at high temps.
https://www.electro-tech-online.com/custompdfs/2006/03/curves-z-y-t-w.pdf
I was told the "25/85" B-constant was 3972, meaning it was taken between 25C and 85C. It was called a "Z-curve" thermistor.
I only know the B-constant formula for NTCs. What's a "Z-curve" and does it have a different formula? I couldn't find any resource on the type outside this mfg. They seem to make high quality devices so I'm not gonna just assume it's an issue of them being poorly made or measured wrong.
Or do all thermistors vary like this once you get out of the 25C/85C range but other mfgs don't characterize them so specifically?
But, there's something weird here. I use the std formula for calculating the device's B constant from any two R-T points and I get very significant difference in the B-constant depending on whether I take it from high temp points or low temp points. Like 3600 at low temps and 4000+ at high temps.
https://www.electro-tech-online.com/custompdfs/2006/03/curves-z-y-t-w.pdf
I was told the "25/85" B-constant was 3972, meaning it was taken between 25C and 85C. It was called a "Z-curve" thermistor.
I only know the B-constant formula for NTCs. What's a "Z-curve" and does it have a different formula? I couldn't find any resource on the type outside this mfg. They seem to make high quality devices so I'm not gonna just assume it's an issue of them being poorly made or measured wrong.
Or do all thermistors vary like this once you get out of the 25C/85C range but other mfgs don't characterize them so specifically?
