Clarify how NI 9467 behaves when GPS signal lost

[ProlucidDavid]

I've deployed a system using an NI 9467 GPS card to ensure data is acquired at top-of-second according to GPS using the Pulse per second (PPS) functionality. My client has asked how the timing system behaves when GPS is not available. My testing indicates that the NI 9467 continues to track time (and produce regular PPS signals) even if it loses GPS connection, but I've had difficulty find documentation describing its behaviour.

Can we confirm PPS signals are still reliable after a GPS signal is lost?
How long will the NI 9467 run with accurate PPS signals in the absence of GPS?
Where can I find documentation that describes the behaviour of NI 9467 when GPS is lost?

[ProlucidDavid · Accepted solution]

I worked with NI support and have the following updates to the questions in bold:

• Can we confirm PPS signals are still reliable after a GPS signal is lost?
  • The NI 9467 PPS signals continue to be generated after signal is lost. Without GPS, drift is expected
• How long will the NI 9467 run with accurate PPS signals in the absence of GPS?
  • The PPS is generated from a 0.5 ppm TCXO and PPS should occur once per second +/- 500 ns under normal operating conditions
  • This case where GPS is lost is not considered a normal operating conditions. No specific details are available on the accuracy of how much drift can be expected in this scenario
• Where can I find documentation that describes the behaviour of NI 9467 when GPS is lost?
  • This documentation is confidential and cannot be shared. Best to reach out to NI support