Lord MicroStrain WSDA-2000, User Manual

Page: 47 / 90

WSDA
®
-2000
User Manual
6. Using the Beacon
In synchronized sampling, the beacon feature is used to coordinate sampling and transmission timing
between multiple nodes. The primary purpose is to avoid data collision, guarantee timing between
samples from different nodes, and to time-stamp the data. The beacon cannot be used in any another
sampling mode.
To acquire tightly synchronized, absolute wireless network times, enable the beacon from the WSN
Beacon On Startup setting in the gateway control panel ( see Configuration on page 36 .) When the
beacon is enabled, the gateway broadcasts a data message once every second containing a
Coordinated Universal Time (UTC) time stamp, and it is used to update each node’s real time clock
(RTC). This continuous synchronization beacon, coupled with the accuracy of the gateway and node
clocks (+/- 3 ppm drift), provides a node- to- node synchronization within ±50 microseconds. The
gateway receives the UTC from the host computer, so the host must be connected to a UTC time
server to achieve that accuracy. There is some lag inherent in the Microsoft Windows distribution of the
UTC. This dictates the overall accuracy of the time-stamp, but the synchronization times between the
gateway and nodes will be consistent because of the accuracy of the embedded RTC clocks.
Nodes must be on the same transmission frequency (channel) as the gateway to receive the beacon
broadcast command. When the beacon is active, the gateway device status indicator will pulse blue
once per second. When the nodes connected to the gateway are in synchronized sampling mode, the
network can be put to sleep by turning off the beacon and then resuming transmitting once the beacon
is enabled. Any node that is actively sampling in synchronized sampling mode on the same frequency
as the gateway will synchronize to it automatically if the beacon is activated.
To avoid interference with other devices it is recommended that the beacon be disabled when not in
use. Do not operate multiple gateways on the same frequency.
To enable and disable the beacon in SensorConnect™, select On or Off from the Toggle Beacon tile. A
green pop up window will appear confirming the successful action. Note: When starting a synchronized
network using SensorConnect™ , it automatically starts the beacon using the host computer's time, not
the gateway's time, which may negatively impact the quality of the synchronized data.
Figure 29 - Synchronized Sampling Beacon
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