6.2VR Assignment

There are five variable resistors (VR) on the PCI-9112 board to allow you making accurate adjustment on A/D and D/A channels. The function of each VR is specified as Table 6.1.

VR1

A/D bipolar offset adjustment

VR2

A/D full scale adjustment

VR3

D/A channel 1 full scale adjustment

VR4

D/A channel 2 full scale adjustment

VR5

A/D unipolar offset adjustment

VR6

D/A reference voltage adjustment

VR7

A/D programmable amplifier offset adjustment

 

Table 6.1 Function of VRs

6.3A/D Adjustment

6.3.1Bipolar Calibration

1.Set the analog input range as : +/- 5V, i.e. the gain = 1 and input mode = Bipolar.

2.Short the A/D channel 0 (pin 1 of CN3) to ground (GND), and connect the TP1 (+) and TP2 (-) with your DVM. Trim the variable resister VR7 to obtain a value as close as possible to 0V.

3.Apply a +5V input signal to A/D channel 0, and trim the VR2 to obtain reading between 4094~4095.

4.Apply a +0V input signal to A/D channel 0, and trim the VR1 to obtain reading flickers between 2048~2049.

5.Repeat step 3 and step 4, adjust VR2 and VR1.

6.3.2Unipolar Calibration

1.Set the analog input range as : 0 ~ 10 V, i.e. the gain = 1 and input mode = Unipolar.

2.Short the A/D channel 0 (pin 1 of CN3) to ground (GND) and connect TP1 (+) and TP2 (-) with your DVM. Trim the VR5 to -5V reading in the DVM.

68 ∙ Calibration