How to use GPS to synchronize measurement at 2 different locations.

[alex.]

The error of the starting time may < 10ns.

[Adam_U]

What types of measurements are you synchronizing? How far apart are the systems?

[alex.]

Need to syn 2 pulse voltage measurement at 2 diffrent places may 10km away.

[jmaczak]

Hi,

You could use two cheap Garmin OEM GPS 18x LVC receivers for around 80 USD each (https://buy.garmin.com/shop/shop.do?pID=27594&pvID=14555).

They "have bare wire for connection to a variety of applications; can output data in NMEA 0183 format (industry standard) or proprietary Garmin format; provides a pulse-per-second logic-level output with a rising edge aligned to within 1 microsecond of UTC time".

You should connect TTL PPS signal to the Counter Input of the DAQ Card and use it as a trigger or timing source. On RS-232 interface you have ASCII info about position and current time (every second). Version 5 PPS is also available.

Details about using GPS for DAQ sync could be found on NI pages. Try "GPS synchronisation.

Important: selecting receiver look for PPS (Pulse-per-Second) signal availlability. 

My app. runs on two PXI's with DSA cards and PXI-6602 as a GPS18xLVC timing interface.

[Adam_U]

The PXI-6682 supports a GPS antenna natively and allows you to both timestamp or create clocks/triggers to drive a DAQ or other module. It also supports IRIG, IEEE 1588 and a PPS.

[MattBradley]

You can also use the PCI V2 from Symmetricom.  (Full disclosure: I wrote the ATE software for it).  I think that in IRIG B DCLS mode it can achieve an accuracy of less than 10 nsec. 

[alex.]

Hi Matt Bradley,

May I know more detail of reference of IRIG B DCLS mode.

Thanks.

[alex.]

When the 6288 is running, it said 12 satellite are available now.

May I know the meaning of 12. Justed learned normally can see 4 only.

Thanks.

[alex.]

Hi JMaczak,

May I know the link of "GPS synchronisation.

Since I can only get 1 6288 cards, have you ever tried to display the PPS's rising edge difference from 2 6288 output to the oscilliscope. Just want to learn how big is the error.

Thanks.

[Adam_U]

This issue is resolved in the soon to be released NI-Sync 3.1 (beta available now.) Basically, you're seeing stale data. If you look at "is time reference present" you should note that it is false indicating GPS sync isn't being used.