National Instruments NI PCI-6110 - Manual (Page 23)

Chapter 3 Hardware Overview
NI PCI-6110/6111 User Manual 3-4 ni.com
Considerations for Selecting Input Ranges
The range you select depends on the expected range of the incoming signal.
A large input range can accommodate a large signal variation but reduces
the voltage resolution. Choosing a smaller input range improves the voltage
resolution but may result in the input signal going out of range. For best
results, match the input range as closely as possible to the expected range
of the input signal.
Input Coupling
You can configure the NI PCI-6110/6111 for either AC or DC input
coupling on a per channel basis. Use AC coupling when the AC signal
contains a large DC component. If you enable AC coupling, you remove
the large DC offset for the input amplifier and amplify only the AC
component. This configuration makes effective use of the ADC dynamic
range.
Analog Output
The NI PCI-6110/6111 supplies two channels of AO voltage at the
I/O connector. The range is fixed at bipolar ±10 V.
Analog Trigger
In addition to supporting internal software triggering and external digital
triggering to initiate a DAQ sequence, these devices also support analog
triggering. You can configure the analog trigger circuitry to accept either
a direct analog input from the PFI0/TRIG1 pin on the I/O connector or a
postgain signal from the output of the PGIA on any of the channels, as
shown in Figures 3-3 and 3-4. The trigger-level range for the direct analog
channel is ±10 V in 78 mV steps for the NI PCI-6110/6111. The range for
the post-PGIA trigger selection is simply the full-scale range of the selected
channel, and the resolution is that range divided by 256.
Note PFI0/TRIG1 pin is an analog input when configured as an analog trigger. Therefore,
it is susceptible to crosstalk from adjacent pins, which can result in false triggering when
the pin is unconnected. To avoid false triggering, make sure this pin is connected to a
low-impedance signal source (less than 1 k
Ω source impedance) if you plan to enable this
input using software.