ALOHA Cabled Observatory
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ALOHA Cabled Observatory
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Aloha Cabled Observatory Engineering Documentation IRIG B Time Card Interface
IRIG-B Time Card Interface The timing for the user experiments is provided by the observatory and is IRIG-B analog. The IRIG-B microcontroller is an interface to a PC104 based IRIG-B time card manufactured by jxi2, Inc. Since the only communications to the shore station is digital serial, there is no analog timing signal available for timing. Therefore, the IRIG timing is programmed by the microcontroller through instructions from the shore station. The IRIG-B generator then free runs from a voltage controlled crystal oscillator which is located in a temperature isolated enclosure for stability. The control voltage is a 16 bit DAC (MAX541) and can program to ~.001 ppm (+/- 2VDC for +/-15 ppm). Although this is functional and operating, the long term accuracy and precision have not been determined because work on the IRIG-B time for the Aloha observatory was in the middle of development at the time of the project work was suspended in 2004. This will be a priority item on observatory development restart.
Rev: 08/10/2007
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