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Getting Started M400E Ozone Analyzer Operator’s Manual
3.3.3. 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.
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 (see
Figure 3-2). Pin-outs for this connector are:
STATUS
1 2 3 4 5 6 7 8 D +
SYSTEM OK
HIGH RANGE
CONC VALID
ZERO CAL
SPAN CAL
DIAG MODE
Figure 3-8: Status Output Connector
Table 3-5: 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.
18 04315 Rev. C1