How does Dynon come up with calibration coefficients

[kurtfly]

Dynon,

I am trying to understand how you come up with the calibration coefficients. It looks like you are using more data than a Skyview user has available to generate the coefficients.
Example: The new 150 PSIG (P255-150G-E4A) pressure transducer you have in the .SFG file the calibration coefficients as a 3rd order polynomial:

y=-20.8757934103442+38.9340680988917*(x)-0.619407933883778(x)^2+0.0956743059068595(x)^3

The transducer manufacture data says typical output is:
Linear, 0.50 Vdc to 4.50 Vdc for 0 to 150PSIG.

This makes the vendor calibration Coefficients as:

y=-18.750+37.5(x)

No other / precise calibration data is provided by the manufacture.

I plotted both of the calibrations and do not see much difference in the EU conversion, but are we giving up some accuracy? Especially at the low end? See difference column below. Are you applying an non-linear characteristic or calibration of the the Skyview system?

I am just curious as I have provided calibration coefficients to others. Want to make sure I am not omitting anything.

 

[Dynon]

I'm not an expert on this, but I believe that it's a bit different because of the internal pull-up resistance that is nominally on those lines.