HP (Hewlett-Packard) PCI-9111DG/HR Manual De Usuario
24
•
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 quite 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.
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 quite 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
Signal
Source
Opertional
Amplifier
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.
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.
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.
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.
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.