Digital outputs, Excitation source, Digital outputs 93 – Campbell Scientific TGA100 Trace Gas Analyzer Manual User Manual
Page 93
8
.
2
)
0
5
(
))
10
(
10
(
)
0
8
.
1
(
10
−
=
−
−
−
−
+
−
=
v
This voltage can be converted back to a concentration as follows:
8
.
1
)
10
(
10
(
)
0
5
(
))
10
(
)
8
.
2
((
0
=
−
−
−
−
−
−
+
=
x
It is extremely important when using the analog outputs to set the data value limits carefully. If the data value exceeds
the voltage range, the analog output will be invalid. However, if the data value limits are set too wide, the 12-bit voltage
resolution may not preserve the resolution of the data value. The data value limits and the output voltage limits are
recorded in the parameter file for future reference.
7.7 Digital Outputs
If the optional 7996 I/O board is installed in the PC, sixteen digital outputs will be available at the screw terminal
connection board. These digital outputs are used to control switching valves in the gradient or site means sampling
modes (see sections 5.1 and 5.2). The outputs will drive up to 24 mA at 2.4 V on the "ON" state and will sink up to 24
mA at 0.5 V in the “OFF” state. These outputs generally must be connected to a relay (such as the A6REL-12 Relay
Driver available from Campbell Scientific) or other mechanical or solid state relay to drive the sampling system valves.
7.8 Excitation Source
A precision 5 Vdc source (100 mA maximum current) is provided on the 9058 Trace Gas Input module mounted in the
electronics chassis inside the analyzer enclosure. This source is normally configured to supply power to a pressure
transducer. This signal is located at the left pin of the connector labeled “EXT”.
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