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Interfacing a DCS/PLC with the Omni FTIR Multi Gas CEMS
Establishing Communications
Digital I/O
C-4
Omni FTIR Multi Gas CEMS Instruction Manual
Figure C–2. Analog Outputs
The FTIR allows the user to access system status conditions via the digital
I/O connections. The digital I/O signals are labelled "DIGITAL OUTPUT
X2" on the electrical panel assembly, which is accessible from the rear of
the rack. The terminals are labelled 1-28.
Pins 1-6 support digital input functionality. A common ground is provided
on pin 1 and the digital inputs are on pins 2-6. The inputs are 5V TTL
signals with a max range of -0.5 to 5.5 VDC, a low threshold of 0.8 VDC
and a high threshold of 2.0 VDC.
Pins 7-28 support digital output functionality. The digital outputs are
provided by solid-state relays with an operating voltage of 0-24 VDC,
maximum load current of 3.5A, minimum load current of 1 mA. The
positive side of the SSRs are the odd numbers and the negative side are the
even numbers. The maintenance status is a physical key switch, not an
SSR.
Refer to
Table C–2
for the digital output assignments and associated rear
panel terminal signal pin outs methods for accessing system status. Refer to
Figure C–3
to locate the pins on the rear panel terminal connector.
Thermo Fisher Scientific
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