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Getting Started Teledyne API – Model T400 Photometric Ozone Analyzer
46
3.3.1.5. Connecting the 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.
ATTENTION
COULD DAMAGE INSTRUMENT AND VOID WARRANTY
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 (Figure 3-9) on the analyzer’s
rear panel, labeled STATUS (Figure 3-4). Each pin’s function is defined in Table 3-6.
STATUS
1 2 3 4 5 6 7 8 D +
SYSTEM OK
HIGH RANGE
CO
N
C
VALID
ZERO CAL
SPAN CAL
DIAG MODE
+5V to external device
Figure 3-9: Status Output Connector
Table 3-6: Status Output Pin Assignments
OUTPUT #
STATUS
DEFINITION
CONDITION
1
SYSTEM OK
ON if no faults are present.
2
CONC VALID
ON if O
3
concentration measurement is valid.
If the O
3
concentration measurement is invalid, this bit is OFF.
3
HIGH RANGE
ON if unit is in high range of DUAL or AUTO Range Modes.
4
ZERO CAL
ON whenever the instrument is in CALZ mode.
5
SPAN CAL
ON whenever the instrument is in CALS mode.
6
DIAG MODE
ON whenever the instrument is in DIAGNOSTIC mode.
7 & 8 Unassigned
D Emitter BUSS The emitters of the transistors on pins 1 to 8 are bussed together.
Spare
+ DC Power + 5 VDC, 300 mA source (combined rating with Control Output, if used).
Digital Ground
The ground level from the analyzer’s internal DC power supplies. This
connection should be used as the ground return when +5 VDC power is used.
06870C DCN6332