The antenna defines the read field. And so also what you do not want to read.
A read field that is too small misses objects. A read field that is too big picks up the racking next to it, and then your registration counts too much. That second one is the hardest, because it only shows up once the numbers turn out to be wrong.
What to look at when you choose
With antennas the shape of the field matters more than the gain in dBi.
- Shape of the field
- A narrow beam for a doorway, a wide field for a table
- Polarization
- Circular if the tags lie in every direction, linear if they all hang the same way
- What has to stay outside
- Often more decisive than what has to be inside: count on shielding
- Mounting
- On a portal frame, against a wall or under a tabletop, and whether that works where you want it
What an antenna does and what it does not do
Wel
- Shape the read field: where yes and where no
- Address several tags at once inside that field
- Be tucked away out of sight, under a worktop for example
- Work together with other antennas on one reader
Niet
- Work on its own: there is always a reader with it
- See through metal
- Make up for too much distance with more power alone
- Stop neighboring tags from reading along, without shielding
More power is rarely the answer. A bigger field also picks up what you did not want, and then you trade a missed object for a wrong number. In the Proof of Value we therefore measure not only whether something is read, but also what comes along that should not.