National Instruments PXI-6683 Series User Manual

Also see for PXI-6683 Series: Installation guide User manual

Contents

GPSGPS stands for Global Positioning System, and it is a system of over two dozen satellites inmedium Earth orbit that are constantly transmitting signals down to Earth. GPS receivers areable to detect these signals and determine location, speed, direction, and time very precisely.GPS satellites are fitted with atomic clocks, and the signals they transmit to Earth containtiming information. This makes the GPS system a precise timing and synchronization source.The PXI-6683 Series has a GPS receiver which powers an active GPS antenna and receivesand processes the RF signals (1.575 GHz) from the satellites. The GPS receiver then generatesa very precise pulse-per-second (PPS) signal that the PXI-6683 Series uses to achieve sub-microsecond synchronization.GPS enables the PXI-6683 Series to synchronize PXI systems located far away from eachother, as long as GPS satellites are visible to the antenna from each location. Furthermore,once the PXI-6683 Series is synchronized to GPS, it can function as an IEEE 1588grandmaster to enable synchronization of external 1588 devices.IRIG-BIRIG is a standard used to transmit precise timing information between instruments to achievesynchronization. IRIG-B is a particular application of the IRIG standard, in which 100 bits ofdata are sent every second. Embedded in the data is a seconds' boundary marker that thereceiving instrument uses to synchronize its timebase to the IRIG source. The rest of the datacontains information such as the time of day, days since the beginning of the year, andoptionally, control functions and the number of seconds since the start of the day, encoded as astraight binary number.The PXI-6683 Series can function as an IRIG-B receiver, supporting synchronization tosources outputting IRIG-B 12X (AM) and IRIG-B 00X (DC), compliant with the IRIG 200-04standard.When configured to synchronize to an IRIG-B AM source, the PXI-6683 Series will be able toaccept a 1 kHz AM modulated IRIG-B 12X signal on its PFI0 input. When configured tosynchronize to an IRIG-B DC source, the PXI-6683 Series will be able to accept an IRIG-B00X DC encoded signal on its PFI0 input.Caution Do not connect an AM signal to PFI0 when the PFI line is configured fordigital operations. This could cause damage to the digital circuitry, the devicedriving the AM signal, or both. Always ensure the line is configured for IRIG-B AMoperation before connecting an IRIG-B AM signal.Furthermore, once the PXI-6683 Series is synchronized to IRIG-B, it can function as an IEEE1588 grandmaster to synchronize external 1588 devices.The following assumptions are made regarding the received IRIG-B signal. All conditionsmust be met for the PXI-6683 Series to be able synchronize accurately:• Seconds begin every minute at 0, increment to 59, and then roll over to 0.• Minutes begin every hour at 0, increment to 59, and then roll over to 0.24 | ni.com | PXI-6683(H) User Manual