National Instruments AT-MIO-64F-5, User Manual

Page: 49 / 266

Chapter 2 Configuration and Installation
© National Instruments Corporation 2-27 AT-MIO-64F-5 User Manual
The common-mode input range of the AT-MIO-64F-5 PGIA is defined as the magnitude of the
greatest common-mode signal that can be rejected. The PGIA can reject common-mode signals
as long as V+
in
and V-
in
are both in the range ±12 V. Thus, the common-mode input range for
the AT-MIO-64F-5 depends on the size of the differential input signal (V
diff
= V+
in
- V-
in
). The
exact formula for the allowed common-mode input range is as follows:
V
cm-max
= ± (12 V - V
diff
/2)
With a differential voltage of 10 V, the maximum possible common-mode voltage is ±7 V. The
common-mode voltage is measured with respect to the AT-MIO-64F-5 ground and can be
calculated by the following formula:
V
cm-actual
=
(V+
in
Ê+ÊÊV-
in
)
2
where V+
in
is the signal at the positive (+) input of the PGIA and V-
in
is the signal at the
negative (-) input of the PGIA. Both V+
in
and V-
in
are measured with respect to AI GND.
Analog Output Signal Connections
Pins 20 through 23 of the MIO subconnector are analog output signal pins.
Pins 20 and 21 of the MIO subconnector are the DAC0 OUT and DAC1 OUT signal pins.
DAC0 OUT is the voltage output signal for analog output Channel 0. DAC1 OUT is the voltage
output signal for analog output Channel 1.
Pin 22 of the MIO subconnector, EXTREF, is the external reference input for both analog output
channels. Each analog output channel must be configured individually for external reference
selection in order for the signal applied at the external reference input to be used by that channel.
Analog output configuration instructions are in the
Analog Output Configuration section earlier
in this chapter.
The following ranges and ratings apply to the EXTREF input:
Normal input voltage range ±10 V peak with respect to AO GND
Usable input voltage range ±12 V peak with respect to AO GND
Absolute maximum ratings ±30 V peak with respect to AO GND
Pin 23 of the MIO subconnector, AO GND, is the ground-reference point for both analog output
channels and for the external reference signal.
Figure 2-11 shows how to make analog output connections and the external reference input
connection to the AT-MIO-64F-5 board.