Internal Monitoring; Built-In Tests; Figure 6 Led Indicators On The Pwc22/52 Board - Vaisala PWD22/52 User Manual

USER'S GUIDE____________________________________________________________________

Internal Monitoring

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Built-in Tests

Extensive, built-in tests are included in the PWD22/52 operation. Various
voltages are measured and corresponding alarm and warning limits are
checked. Optical contamination of both the transmitter and the receiver is
continuously monitored by measuring the backscattered light. For this
purpose an additional transmitting LED is installed in the receiver.
The software generates alarms, if visibility is less than a given limit.
PWD22/52 generates warnings of suspected faulty hardware. If a fatal
hardware failure is detected, visibility data is not generated; it is
substituted with slashes (/////). A status message displays the cause of the
error in status bits.
Built-in tests include memory test, analog monitoring, and signal
measurement monitoring. Results of the monitoring measurements are
displayed in volts or hertz depending on their origin.
Program operation is monitored by the watchdog circuitry. If the circuit
is not triggered in about two seconds, it will perform a hardware reset.
Figure 6 LED Indicators on the PWC22/52 Board
Normal operation is indicated by the Run LED blinking once every
second. The Signal/Offset LED is on, when PWD22/52 measures the
visibility signal.
The RxD and TxD LEDs are directly controlled by the serial line
hardware indicating all action in the serial line.
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