Chapter 3
Signal Connections
© National Instruments Corporation
3-5
DAQCard-500 User Manual
Floating Signal Source
Grounded Signal Source
Examples
• Isolated outputs
• Battery devices
• Thermocouples
Floating Measurement System
Example
• Battery powered laptop
Grounded Measurement System
Example
• Desktop computer connected
to building ground
Example
• Nonisolated instruments
- Building (Earth) Ground
+
-
+
-
Signal
Mux
AIGND
(2)
(3)
(4)
(5)
(9)
(1)
DAQCard-500
+
-
+
-
Signal
Mux
AIGND
(2)
(3)
(4)
(5)
(9)
(1)
DAQCard-500
+
-
+
-
Signal
Mux
AIGND
(2)
(3)
(4)
(5)
(9)
(1)
DAQCard-500
+
-
+
-
Signal
Ground
Current
Mux
AIGND
(2)
(3)
(4)
(5)
(9)
(1)
DAQCard-500
NOT RECOMMENDED
Figure 3-2. DAQCard-500 Analog Input Connections
Digital I/O Signal Connections
Pins 12 through 19 of the I/O connector are digital I/O signal pins. Pins 12 through 15 are digital
input pins. Pins 16 through 19 are digital output pins. Pin 27 is the digital ground pin.
The following specifications and ratings apply to the digital I/O lines.
•
Absolute maximum voltage input rating
+5.5 V with respect to DGND
•
Absolute minimum voltage input rating
-0.5 V with respect to DGND