4 GPS Clock
IRSA - Intelligent Reference Selection Algorithm
IRSA stands for an Intelligent Reference Selection Algorithm. In case that a master signal fails the IRSA takes
care that the switching to the next reference signal in the priority list runs automatically and smoothly. The
IRSA also takes into account the highly stable holdover performance of the local oscillator. It ensures that
switching from the superior reference signal to the less accurate one is delayed as long as the highly stable
oscillator can provide better accuracy in holdover than the next available reference signal in the priority list.
To ensure that IRSA is working properly, follow these steps:
1.
Configure a priority list of available reference signals in descending order from the superior to inferior
one in the MRS Settings menu (see chapter MRS Source Priority).
2.
Activate IRSA in the IRSA menu. As per default the IRSA is deactivated.
3.
Fill in the estimated precision values for the input reference signals in for this provided precision fields.
The precision value will determine the holdover time when switching to the next reference source if the current
master is not available.
Here are some estimated precision values which you can load as defaults:
- GPS / GNSS as the first priority has the highest estimated precision :100 ns
- ext. Osc. (e.g. Rubidium): 120 ns
- PTP IEEE 1588: 100 ns
- PPS plus string: 100 ns
- NTP: 100 us
IMS-GPS180 Setup Guide
Date: 10th January 2018
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