Masterclock GPSPCI Spécifications télécharger pdf (Page 9)

CHAPTER 2. NETWORK PERFORMANCE MEASUREMENTS SYSTEMS 8

• Accuracy of 10ms on the client side

• Require external time reference (GPS receiver, dial-up, CDMA digital receiver)

• One or more 1Hz PPS and 10MHz outputs redistributed from the GPS

• Compatible with NTP v2,v3 or v4 (with asymmetric encryption)

• Multiple network interfaces

• High quality internal oscillator in case of failure of primary time reference

• Rack-Mountable Unit

As you can see all of these devices need some sort of external time reference. Using a

GPS receiver or some other kind of source, they can provide accurate time to a network of

computers. The accuracy obtained in the default setup is around 10ms.

2.2.3 GPS Receivers

There are many GPS receivers on the market, most of them having the features needed for

network time synchronization. The most important features are a good precision and the

availability of the PPS signal that is used by most procedures. The receiver should also

provide the full time information on request. Some receivers are prese nted below:

• Motorola Oncore, Trimble Ac utime, Jupiter-T, TAC-2 kit, Meinberg GPS PCI Card

Figure 2.4: Sample GPS receiver

The common features are:

• Very accurate (100ns) 1Hz PPS outputs (100PPS for Motorola Oncore)

• Monitoring software (some of them have LCD displays)

• Multiple simultaneous channels

• NMEA Ascii outputs (with the full UTC time information)

• Acquisition time (initial synchronization time): 5 - 20 minutes (cold boot, no data

known)

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Masterclock GPSPCI Spécifications Page 9