The DL850 is capable of linearizing an input signal using the Polynomial Feature in the /G3 Realtime Math option. The polynomial feature performs a fourth order polynomial calculation on the selected source waveform. To linearize the input signal using the Polynomial Feature, follow the procedures listed below:
Please download and view the attached files for a demonstration of the Polynomial feature on the DL850. The attached example details a thermistor that has been conditioned to produce a duty-cycle variation on a square wave. The duty-cycle as a percentage is NOT linear with respect to the value of the thermistor temperature.
The individual polynomial coefficients can be saved as a setup file on the DL850. The attached Excel worksheet contains the parameters and the error calculation for each duty cycle. For a quick online calculator that can be used as a reference for the coefficient calculation, click on the link provided.
The square wave pulse train is decoded by the Duty Cycle feature of the /G3 Realtime Math. The resulting waveform is again processed using the polynomial feature to linearize the input signal. Thus the temperature measurement is linear to the duty-cycle and the remaining error due to linearization is known for each value of duty-cycle input.