Timing and Synchronization
Time synchronization of the instrument is crucial to ensure the quality of the seismic data stream. Our sensors offer a redundant system using a combination of low-latency NTP and external GPS time stamping.
Furthermore, QuakeSaver sensors determine the intrinsic clock drift of the system in correlation with the ambient temperature to constantly correct skew and correct the system's clock. The system will learn the clock drift and provide more accurate timestamps the longer the system is deployed.
Network Time Protocol (NTP)
The network time protocol (NTP) and its implementation has evolved over the years to provide precisions less than a millisecond. We leverage these modern implementations (i.e. chrony) together with continuous quality control to ensure reliable time stamping over the seismic network.
GNSS HiDRA only
An external GPS receiver can be used for time stamping. Using precise PPS interrupts this solution guarantees precise clock synchronization in connected and off-line environments.
Status LEDS
The instruments communicate their status through LEDs. Particularly important is the time synchronisation and acquisition state.
QS MEMS
The QuakeSaver MEMS has a single RGB LED for status reporting. The startup sequence flashes red, green, blue and signals the startup of the acquisition software.
| Signal | Status |
|---|---|
| Green flash | Time is synchronized. |
| Blue flash | Time is synchronized, sensor is connected to network. |
| Red fast flash | System Error |
QS HiDRA
The QuakeSaver HiDRA has three LEDs for status reporting. The startup sequence cycles the LEDs nad signals the startup of the acquisition software.
| Signal | Status |
|---|---|
| Power on | System is powered and acquisition software running. |
| Acquisition flash | System is acquiring data |
| Sync/Online first flash | Time is synchronized. |
| Sync/Online second flash | Time is synchronized and system is online |
The first and single flash refers to synchronizity with the acquistion flash.
Time Synchronisation Decision Tree
To decide whether the system is synchronized through NTP or PPS (GPS Receiver) we analyse the time sources of the system.
Details
For time management and synchronisation of the instrument system clock we rely on the customized chrony daemon.
More information at https://chrony-project.org/.