Teledyne 9110TH - Nitrogen Oxides Analyzer - Manual (Page 169)

Operating Instructions Model 9110TH NOx Analyzer
Teledyne Analytical Instruments 149
4.15. Remote Operation
4.15.1. REMOTE OPERATION USING THE EXTERNAL DIGITAL I/O
4.15.1.1. 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
(PLCs). 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 PLCs 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 through a 12 pin connector on the analyzer’s rear panel
labeled STATUS (see Figure 6-17). The function of each pin is defined in Table 6–29
COM
M
ON
EMITT
E
RS
STATUS
1 2 3 4 5 6 7 8 D +
SY
S
T
E
M
O
K
HIGH
RA
NGE
C
O
NC
V
A
LI
D
ZERO CAL SPA
N
CAL
DIA
G
MOD
E
LO
W
S
P
AN
GROUND
Figure 4-15: Status Output Connector