Z-World eDisplay OP7200, Руководство пользователя

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26 eDisplay (OP7200)
with the attenuator reference selection jumper in the desired position (see Figure 10). If a
calibration is performed and the jumper is subsequently moved, the corresponding input(s)
must be recalibrated. The calibration table 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.
It is not necessary to fill out the entire calibration table. Only the entries associated with
the modes, channels, and gains that you will be using are necessary. This fact can be used
to simplify and speed up the calibration process.
Each calibration is normally done at 10% less than the maximum and 10% more than the
minimum within a given voltage range defined by the mode, channel, and gain. However,
if an application is known to use only portion of a particular range, it is possible to obtain
improved accuracy by using calibration points that are 10% less than the expected maxi-
mum and 10% greater than the expected minimum.
3.4.3.4 Factory Calibration
Because of the large number of possible calibrations, the factory performs only a rudimen-
tary calibration on the unit. By default, all four of the attenuator reference selection jump-
ers are in the analog ground position. The factory performs a single-ended calibration on
each of the eight channels with a gain of 1 (0–20 V range). The remaining single-ended
calibration constants for the other seven gains are approximated and are filled in based on
the initial calibration. The milli-amp and differential portions of the table are filled in
using typical expected values. All read routines will work properly with these factory-ini-
tialized calibration constants, but only the single-ended mode should be expected to return
accurate results over a range of 0–20 V until you recalibrate the OP7200 for your use.
Sample programs are provided to illustrate how to read and calibrate the various A/D
inputs for the three operating modes.
These sample programs are found in the
ADC
subdirectory in
SAMPLES\OP7200
. See
Section 4.7, “Sample Programs,” for more information on these sample programs and how
to use them.
Mode Read Calibrate
Single-Ended, one channel ADRD_SE_CH.C ADCAL_SE_CH.C
Single-Ended, all channels ADRD_SE_ALL.C ADCAL_SE_ALL.C
Milli-Amp ADRD_MA_CH.C ADCAL_MA_CH.C
Differential, analog ground ADRD_DIFF_GND.C ADCAL_DIFF_GND.C
Differential, 2 V reference ADRD_DIFF_2V.C ADCAL_DIFF_2V.C