Tham khảo tài liệu 'electronic navigation systems 3e episode 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Speed measurement 79 Built-in test circuitry In common with most computer-controlled equipment the system operates a self-test procedure every time it is switched on and performs a fault detection routine at regular intervals during operation. Fault diagnosis routine and testing can be performed manually via the Master Display Unit keypad. During a manual test sequence all LEDs are illuminated and the LCD digits are sequentially displayed. If the test is successful PASS is displayed in the Distance display. If not a fault code number is displayed. As an example of this the number 402 indicates that the Water Temperature reading is faulty and that the probable faulty component is the temperature sensor in the transducer or the wiring between it and the processing card 2A1. As a further indication of the depth to which the system is able to diagnose faults the other codes are listed below. Codes 101 or 102 keypad faults in the Master Display Unit. Codes 201-208 communication faults between the Display Unit and the Main Electronics Unit. Codes 255 and 265 RS-232 422 outputs faulty from the Display Unit. Codes 301-308 and 355-365 refer to faults in the Main Electronics Unit. Codes 401-403 temperature measurement faults. Codes 490 and 491 memory test faults. Codes 520-524 transmit receive ping faults. Codes 600-604 and 610 - 614 noise level and sensitivity faults. Codes 620-630 receive transmit signal faults. Output data formats Output data sent to remote navigation systems is formatted in the standard protocol for Interfacing Marine Electronics Navigation Devices developed by the National Marine Electronics Association NMEA 0183 see Appendix 3 for full details . A second output in Sperry Marine Format is intended primarily for the direct printout of speed data. Display unit - serial data output format The serial data output port of each display is configured so that the data can be communicated to peripheral processing devices. Data can be interfaced using RS-232 or .
