26
•
Operation Theorem
Analog Input Signal Connection
The PCI-9111 provides 16 single-ended analog input channels. The analog
signal can be converted to digital value by the A/D converter. To avoid ground
loops and get more accurate measurement of A/D value, it is q uite important to
understand the signal source type. The single-ended mode has only one input
relative to ground and is suitable for connecting with the
floating signal source
.
The floating source means it does not have any connection to real ground. The
following figure shows the single-ended connection. Note that when more than
two floating sources are connected, the sources must be with common ground.
AIN
AGND
n = 0, ..., 15
Floating
Signal
Source
Opertional
Amplifier
To A/D Converter
Input Multipexer
...
V1
V2
Signal Channel Control
There are two ways to control the channel number. The first one is the
software programming and the second one is the auto channel scanning which
is controlled by the ASCAN bit in AD mode control register. As ASCAN is
cleared (0), the value of AD channel MUX register defines the channel to be
selected. Only one channel can be selected in this situation.
As ASCAN is set (1), the value in AD channel MUX register defines the ending
channel number of auto-scanning operation. Under auto scan mode, the
channel is scanning from channel 0 to the ending channel. Whenever a trigger
signal is rising, the channel number to be selected will increase automatically.
For example, if the ending channel number is 3, the auto channel scanning
sequence is 0, 1, 2, 3, 0, 1, 2..., until the ASCAN bit is cleared.
The current A/D channel number could be read back from the A/D data register
on 12 bits PCI-9111 DG but it is not possible to be read back for PCI-9111HR.
Note that the MUX register is 8 bits. The 4 LSBs is used to select the
multiplexer on board. The 4 MSBs could be sent out via the EDO pins of the
CN3 connector to select the external daughter board. At most 16 daughter
board can be selected and total 256 channels can be selected without extra
circuits.
Summary of Contents for NuDAQ PCI-9111DG
Page 1: ...NuDAQ PCI 9111DG HR Multi Functions Data Acquisition Card User s Guide ...
Page 4: ......
Page 10: ......
