Chapter 3 ______________________________________________________ Functional Description
VAISALA _______________________________________________________________________ 27
Internal Monitoring
Built-in Tests
Built-in tests are included in the PWD22/52 operation to measure various
voltages and check the corresponding alarm and warning limits. Optical
contamination of both the transmitter and the receiver is continuously
monitored by measuring the backscattered light. An additional
transmitting LED is installed in the receiver for this purpose.
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.
Watchdog circuitry monitors program operation. If the circuit is not
triggered in about two seconds, it performs a hardware reset.
1206-026
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.
To Next Page
Loading...
