Z-World Wolf BL2600, Руководство пользователя

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User’s Manual 27
also affects the resolution of the 4–20 mA current outputs—you need to configure a volt-
age output for unipolar operation if you want 12-bit resolution on the associated current
output.
There are other effects on a current output when the associated voltage output is operating
in the bipolar mode. While voltages of 0 to +10 V still correspond to currents of 4 to 20 mA,
the current cannot be determined reliably for voltages below 0 V, and will be “negative” at
voltages below -2.5 V. Thus the current output effectively becomes a “current sink”
instead of a “current source.”
The D/A converter outputs are factory-calibrated and the calibration constants are stored in a
separate EEPROM.
3.5.1 D/A Converter Calibration
To get the best results form the D/A converter, it is necessary to calibrate each mode (uni-
polar, bipolar, and current) for each of its gains. It is imperative that you calibrate each of
the D/A converter outputs in the same manner as they are to be used in the application.
The calibration table in software only holds calibration constants based on unipolar, bipo-
lar, and voltage or current operation.
Other factors affecting the calibration must be taken into
account by calibrating using the same mode and voltage/current setup as in the intended use.
Sample programs are provided to illustrate how to calibrate the various D/A outputs for
the three operating modes.
These sample programs are found in the
DAC
subdirectory in
SAMPLES\BL2600
. See
Section 4.2.5 for more information on these sample programs and how to use them.
Mode Calibrate
Voltage
DAC_CAL_VOLTS.C
Current
DAC_CAL_MA.C