TagMaster XT Mini, Manual

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XT-1/XT Mini Manual 13-111 05, 2015-08-14
Page 7 of 32
The reader's radiation pattern or read lobe (the region where the reader can read tags) is shaped like a
balloon in front of the reader as shown in Figure 4. The maximum read range is obtained when the tag is at
the tip of the balloon. At or close to this point, the width of the balloon is very small, which means that the
tag has to be accurately positioned to be read. It is recommended to mount the reader such that the tag
can be read at the widest part of the balloon which is at around 60-70% of maximum read range. If
required, the maximum read range can be reduced as described in section 4.3.1.
The reader should be mounted such that there is free sight
between the reader and the tag. Radio waves from the reader
cannot pass through metal or objects containing water (such as
humans). Metallic objects close to the reader may cause
reflections that can significantly reduce the read range.
Different tags have different mounting requirements. ISO card tags
are generally optimized for free air and - if used in a car - should
be mounted in a card holder that creates an air gap between the
tag and the windshield. Windshield tags must be mounted on the
windshield for optimal performance. Typical tags do not work if
they are mounted on metal or objects containing water. Metallized
windshields may prevent tag reading as they block radio waves.
Most EPC Gen 2 tags have a donut shaped radiation pattern as shown in Figure 5. This means that the
tags can be read not only when the front side is facing the reader, but also when the backside or long
edges are facing the reader. If the tag is turned such that one of the short edges is facing the reader, the
read range drops rapidly.
If the reader is mounted beside the car, the tag should be mounted with the donut lying as shown in the left
part of Figure 5. Note that the tag can be mounted in the windshield and read when the long edge of the tag
is facing the reader. If the windshield is metallized, the tag can be mounted in the side window or on the
front of the B-pillar (with a suitable holder creating a distance from the metal). A side-mounted reader
together with a tag with a lying donut can be used to cover a wide road as shown in Figure 3 B.
If the reader is mounted above or in front of the car, the tag should be mounted with the donut standing as
shown in the right part of Figure 5. In a multilane installation (Figure 2 B) it is recommended to mount the
tags like this with the reader above the car to reduce the risk of cross reads. If the windshield is metallized,
a transparent tag can be mounted on the headlight.
Figure 5 Tag radiation patterns and example placement
Figure 4 XT-1 radiation pattern