Advantech PCI-1718 Series User Manual

Connect a reference voltage within the range ±10 V to the reference input 
of the D/A channel you want to calibrate. You can use either the on-board 
-5 V (-10 V) reference or an external reference. Adjust the full-scale gain 
and zero offset of the D/A channel with VR5 and VR6, respectively. Use 
a precision voltmeter to calibrate the D/A output.

Set the D/A data register to 0 and adjust VR6 until the output voltage 
equals 0 V.
Set the D/A data to 4095 and adjust VR5 until the D/A output voltage 
equals the reference voltage minus 1 LSB, but with the opposite sign, For 
example, if V

ref

 is -5 V, then V

out

 should be +4.9988 V.