User`s manual
XP850032 s I/O Configurations
Step 8. Recalibrate the XP8500
To recalibrate an XP8500, apply two known test voltages to each channel,
chan, to be used. Get the converted reading for each test voltage and pass
the readings and the test voltages, to the function adc4
_
compute to
calculate the conversion coefficients, zero
_
offset and invgain, for
that channel. adc4
_
compute will automatically store the coefficients in
an adc4coeff structure (be sure to declare an adc4coeff structure for
each channel to be calibrated). Lastly, pass the new conversion coeffi-
cients to the function adc4_writecoeff to store them in the appropriate
locations in the XP8500s EEPROM.
The sample program ADC4SMP3.C in the Dynamic C SAMPLES\PLCBUS
subdirectory shows how to calibrate the first four channels of an XP8500
board manually, assuming test voltages of 1.00 V and 9.00 V.