ADLINK ACL-8111 - Manual (Page 57)

Calibration • 51
6.2 VR Assignments
There are five variable resistors (VR) on the ACL-8111 board to allow
you making accurate adjustment on A/D and D/A channels. The function
of each VR is specified below:
VR No. Function
VR1 D/A full scale adjustment
VR2 D/A zero offset adjustment
VR3 A/D offset adjustment
VR4 A/D full scale adjustment
VR5 A/D programmable amplifier offset adjustment
6.3 D/A Calibration
The D/A input reference voltage should be connected to for calibration. You
may use the JP1 to select the -5V or -10V reference. The zero offset and full
scale of D/A channel can be turned through VR1 and VR2. The full-scale
gain of D/A is adjusted by VR1, and zero offsets are adjusted by VR2.
Note: A precision voltmeter to measure the D/A output is very important.
The procedures of calibration are as follows:
Full scale adjustment :
1. Set JP1 to select -5V as reference voltage.
2. Connect VDM (+) to CN1 pin 30 and VDM (-) to A.GND.
3. Write digital data '4095' (0x0FFF) into D/A's digital data Register
(BASE+4 and BASE+ 5).
4. Adjust VR1 until your voltmeter's voltage reading is equal to +5V
(reference voltage with opposite sign).
Offset zero adjustment:
1. Write digital data ' 0' (0x0000) to D/A's digital data register (BASE+4 and
BASE+ 5).
2. Adjust VR2 until the your voltmeter's voltage reading is 0V.