User Manual

40 System Installation PLUS System Manual
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Figure 2-30: Inadequate Calibration Tag Coverage
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Figure 2-31: Adequate Calibration Tag Coverage
Select locations for Calibration Tags where they can be heard reliably by as many Readers as
possible. However, be careful to avoid paths that are subject to blockage, reflections, and grazing
angles through walls. Mount the Calibration Tags horizontally whenever possible. Ceiling mounted
tags generally do not propagate as far as tags mounted 1-2’ lower than ceiling height.
2.5.2 Checking Calibration Tag Statistics
In this step we will check the RX%, RSSI, and TDOA for the Readers that we intend to calibrate with
a given Calibration Tag. RX% is a measurement of data throughput of one Tag to one Reader – it
provides the ratio of the number of packets received to the number of packets sent, expressed as a
percentage. RSSI is the Received Signal Strength Indicator, an arbitrary measurement of Tag signal
strength on a scale from 0 to 255. TDOA is the Time Difference of Arrival of the tag signal as
compared between two Readers. The TDOA for a stationary Tag with a good signal path should
change very little.
After placing a Calibration Tag in its candidate location, open the Visualizer Tag Configuration
window from the Settings menu. Locate the ID of the Calibration Tag in the list. Under the Cal Tag
column, select ―Yes‖ to indicate that this is a Calibration Tag. Since this is a test case, it is not
necessary to enter survey information at this time. Or, you may wish to enter an approximate location