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Chapter 8 Tutorial
Multifunction Module
Multifunction Module
Digital Input
The HP 34907A module has two non-isolated 8-bit input/output ports
which you can use for reading digital patterns.
You can read the live status of the bits on the port or you can
configure a scan to include a digital read.
You can generate an alarm when a specific bit pattern or bit pattern
change is detected on an input channel. The channels do not have to be
part of the scan list to generate an alarm.
The internal +5V pull-up circuitry allows you to use the digital input
to detect contact closures like micro-switches or limit switches.
An open input floats to +5V and is read as a "1". An input shorted to
ground is read as a "0". An example of a contact closure detection
channel is shown below.
Digital Read
392
+5 V
10 k
I/O Line (1 of 8)
+
+TTL
–
Reference
(+2.1 V)
Limit Switch
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