Operating Instructions
Model 300E Carbon Monoxide Analyzer
Instruction Manual
86
P/N 04288 REV: A
6.6.6.
Flow Calibration
This procedure allows the user to calibrate the flow sensing circuitry of the analyzer
to match the flow reported by an independent flow meter connected to the Sample
inlet of the analyzer. See Section 9.3.5 for instructions on performing this
calibration.
6.7. External Digital I/O
6.7.1.
Status Outputs
The Status Outputs report analyzer conditions via optically isolated NPN transistors,
which sink up to 50 mA of DC current. These outputs can be used interface with
devices that accept logic-level digital inputs, such as Programmable Logic
Controllers (PLC’s). Each Status bit is an open collector output that can withstand
up to 40 VDC. All of the emitters of these transistors are tied together and available
at D.
NOTE
Most PLC’s have internal provisions for limiting the current that the input will draw from
an external device. When connecting to a unit that does not have this feature, an
external dropping resistor must be used to limit the current through the transistor
output to less than 50 mA. At 50 mA, the transistor will drop approximately 1.2V from
its collector to emitter.
The status outputs are accessed via a 12-pin connector on the analyzer’s rear panel
labeled STATUS. The function of each pin is defined in Table 6–4.
STATUS
1 2 3 4 6 7 8 - +5
Figure 6–4: Status Output Connector