Teledyne 100AH Display Brownout, Status Output Lines, External Contact Closures, 10-39

Teledyne API Model 100AH SO2 Analyzer Instruction Manual, 02417, Rev. D

10.3.3.2 Display Brownout

During low AC line conditions the display can lock up due to insufficient voltage. When low line conditions are approaching, this circuit senses the condition by monitoring the un-regulated +5 VDC in the Power Supply Module. If brownout conditions are met, the DISP_BROWNOUT line is asserted and the CPU sends a hardware RESET command to the display and sends a BRNOUT RESET pulse back to U4. Brownout conditions will be noticed by the display flashing every 8 seconds.

10.3.3.3 Status Output Lines, External Contact Closures

The Status lines consist of 2 active input lines, and 12 active output lines. Additional circuits are present on the board but currently unused. Individual lines are set or cleared under CPU control depending on the assigned alarm condition. The CPU also monitors the 2 input lines for remote calibration commands. The status inputs and outputs are terminated at the rear panel. (See schematic diagram 01917, Figure 2-2and Figure 4-3for details.)

The output lines are opto-coupled NPN transistors which can pass 50 ma max of direct current with a voltage of 30 VDC max (see Schematic 01087).

The input lines are optically isolated with inputs pulled up to +5 VDC. External contacts can be contact closures or open channel transistor contacts. DO NOT apply any voltage, since +5 VDC is supplied internally (refer Figure 2-2and Schematic 01087 for details).

Individual status lines can be set or cleared using the DIAGNOSTIC mode SIGNAL I/O. This can be useful for simulating fault conditions in the analyzer to see if external circuitry is working correctly. See Table 4-3for pin assignments.

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