4 
O p e r a t i o n T h e o r e m
The operation theorem of the functions on PCI-9112 card is described in this chapter. The functions include the A/D conversion, D/A conversion, Digital I/O and counter / timer. The operation theorem can help you to understand how to manipulate or to program the PCI-9112.
4.1A/D Conversion
Before programming the PCI-9112 to perform the A/D conversion, you should understand the following issues:
ØA/D front-end signal input connection
ØA/D conversion procedure
ØA/D trigger mode
ØA/D data transfer mode
ØSignal Connection
4.2Analog Input Signal Connection
The PCI-9112 provides 16 single-ended or 8 differential analog input channels. The analog signal can be converted to digital value by the A/D converter. To avoid ground loops and get more accuracy measurement of A/D conversion, it is quite important to understand the signal source type and how to choose the analog input modes : signal-ended and differential. The PCI-9112 offers jumpers to select 16 single-ended or 8 different analog inputs.