WSDA
®
-200-USB
User Manual
3.2
Change Frequency
There are 14 available frequency channels between 2.405 and 2.470 GHz. Wireless nodes and the
gateway must be on the same frequency channel to communicate.
To move node(s) to a different frequency, select Base Station and then the Change Frequency tile.
Figure 16 - Gateway Frequency
3.3
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.
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.
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
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