Example: SPice10212 nonlinearity correction

This program demonstrates the polynomial method of linearizing the raw readings. Note that the actual coefficients used are specific to our test transformer. You must determine your own coefficients and use them in your program. Only one channel has been linearized. The program uses the MMi99/200 LCD for display.

;Correct.spt SPice20212 demo/calibration with nonlinearity correction 
;using MMi200 with LCD
;The nonlinearity correction is applied only
;to the first channel, to allow comparisons to be made.

;RAM storage
Temp            EQU             20

;Use for MS12 only              ON              20      ;MS12 backlight

;Initialize the SPice connector for 3 analog inputs
                SetU            0,3
                SetU            1,3
                SetU            2,3
                SPiceConfigU

;Main program loop:

Loop:
;This section displays the raw analog readings on the
;top line of the display. Full scale is always 255 counts

                AnInE                   ;Use AnInC on MS12
                OBLCD_SetCur    0,0
                OBLCD_UDecDispXFW

                AnInF                   ;Use AnInD on MS12
                OBLCD_SetCur    0,6
                OBLCD_UDecDispXFW

                AnInG                   ;Use AnInE on MS12
                OBLCD_SetCur    0,12
                OBLCD_UDecDispXFW

;This section displays the readings as voltages.

;For phase A the conversion is done using a correction algorithm
;based on a polynomial function. 

;For the other two phases the conversion is a simple scaling.
;The scale factor initially loaded into Q will determine the
;full scale range, i.e. the voltage corresponding to 255
;raw counts.

                AnInE                   ;Use AnInC on MS12
                GoSub           Correct
                OBLCD_SetCur    1,0
                OBLCD_UDecDispXFW

;The scale factor for the other two readings
;is Vfs/255, where Vfs is the required full scale voltage.

                fLoadQ          1.0     ;1.0  for FS=255V (240V+10%)
                                        ;0.5176 for FS=132V (120V+10%)

                AnInF                   ;Use AnInD on MS12
                OBLCD_SetCur    1,6
                Float
                fMul
                OBLCD_fDispW    3,0

                AnInG                   ;Use AnInE on MS12
                OBLCD_SetCur    1,12
                Float
                fMul
                OBLCD_fDispW    3,0



                GoTo            Loop


;Correct for nonlinearity

;Implements the function 

;y = 2.859320E-06 x^3 -1.011672E-03 x^2 +1.058639E+00x +3.916506E+00

;These particular coefficients were determined with a specific transformer,
;with the system calibrated for 255V full scale. A different transformer
;and/or full scale range will require different coefficients.

Correct:
                Float
                fStore          Temp
                fLoadQ          2.859320E-06            ; X^3 coefficient
                fMul
                fLoadQ          -1.011672E-03           ; X^2 coefficient
                fAdd
                fRecallQ        Temp
                fMul
                fLoadQ          +1.058639E+00           ; X^1 coefficient
                fAdd
                fRecallQ        Temp
                fMul
                fLoadQ          +3.916506E+00           ; constant offset
                fAdd
                fLoadQ          0.5                     ;Rounding
                fAdd
                Fix
                Return