A/D Converter Calibration - Rabbit RabbitCore RCM3400 User Manual

B.4.3.3 A/D Converter Calibration
All single-ended inputs are factory-calibrated with actual voltages at a gain code of 0.
Typical values for the other gain codes and for other calibration constants for current and
differential measurements are used to populate the table to allow A/D conversions to be
done "out of the box." To get the best results form the A/D converter, it is necessary to
calibrate each mode (single-ended, differential, and current) for each of its gains. It is
imperative that you calibrate each of the A/D converter inputs in the same manner as they
are to be used in the application. For example, if you will be performing floating differen-
tial measurements or differential measurements using a common analog ground, then cali-
brate the A/D converter in the corresponding manner. The calibration must be done with
the attenuator reference selection jumper in the desired position (see Figure B-6). If a cali-
bration is performed and the jumper is subsequently moved, the corresponding input(s)
must be recalibrated. The calibration table in software only holds calibration constants
based on mode, channel, and gain. Other factors affecting the calibration must be taken
into account by calibrating using the same mode and gain setup as in the intended use.
Sample programs are provided to illustrate how to read and calibrate the various A/D
inputs for the three operating modes.
Mode
Single-Ended, one channel
Single-Ended, all channels
Milli-Amp, one channel
Differential, analog ground
These sample programs are found in the
Section 3.2.2 for more information on these sample programs and how to use them.
User's Manual
Read
—
AD_RDVOLT_ALL.C
AD_RDMA_CH.C
AD_RDDIFF_CH.C
SAMPLES\RCM3400\ADC
Calibrate
AD_CAL_CHAN.C
AD_CAL_ALL.C
AD_CALMA_CH.C
AD_CALDIFF_CH.C
subdirectory. See
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