Справочник Пользователя для Agrident Corporation ASR700
05.07.2007
Page 50 of 56
ASR700 Reader Operation
8.5 Fluorescent and Low Voltage Lighting
Both types of lighting can on rare occasions produce interference.
Some fluorescent lights generate radio frequencies, but the emission levels are generally small.
We have come across Low Voltage lighting systems that generate high emission levels in their
"transformer" module, which actually contains a switch-mode converter. These do not meet cur-
rent EMC regulations, but may have been legal when installed.
Some fluorescent lights generate radio frequencies, but the emission levels are generally small.
We have come across Low Voltage lighting systems that generate high emission levels in their
"transformer" module, which actually contains a switch-mode converter. These do not meet cur-
rent EMC regulations, but may have been legal when installed.
8.6 Other readers
One potential source of interference that is easily overlooked is other readers, and other prod-
ucts that use the same frequency band. Low power products are restricted to a few frequency
bands, so there may be cases where two legitimate products are trying to use the same band.
An ISO HDX tag will not read properly if it is picking up transmissions from two different ISO
readers that are not synchronised. Nearly always it won't respond at all, but if it has started re-
sponding to one it may give peculiar responses to both.
(ISO tags do not respond to signals from tagging systems such as shop-door systems, but the
reading range my be affected by their signals.)
ucts that use the same frequency band. Low power products are restricted to a few frequency
bands, so there may be cases where two legitimate products are trying to use the same band.
An ISO HDX tag will not read properly if it is picking up transmissions from two different ISO
readers that are not synchronised. Nearly always it won't respond at all, but if it has started re-
sponding to one it may give peculiar responses to both.
(ISO tags do not respond to signals from tagging systems such as shop-door systems, but the
reading range my be affected by their signals.)
8.7 Effects of metal near readers
Usually metal near the antenna of a reader which reduces performance, but it is possible to use
the effects of metal to advantage.
Metal close to an aerial loop can act as a short circuit, sucking energy out of the reader. It will
affect the tuning of the antenna, but even if the antenna is returned there could still be a loss of
range. The reading zone will change its shape, with the range behind the metal reduced.
The effect on the reading range is greater when the metal is closer to the antenna loop. Many
factors affect the range, but typically a complete sheet of metal, 100 mm (4 inches) behind the
antenna loop, reduces the reading range by about 25%. (If the metal is ferrous, it will have
slightly more effect.) This is after the antenna loop has been retuned.
When the metal is only close to part of the loop, the effect is reduced. If the metal is only close
to one side of the loop the effect is minimal.
As metal affects tuning, metal doors can pose a problem. If the antenna loop is too close, it’s
tuning will change when the doors are open. If the tuning is optimised when the doors are open,
the range will drop when the doors close (or vice versa).
Ferrous metal (e.g. steel) introduces new considerations. A sheet of ferrous metal reduces the
reading range by more than non-ferrous metal. It also acts as a better screen, with the range
behind the metal reduced to around 50% of the range in front. The shape of the reading zone
behind the metal is distorted, making the region where tags will be read less predictable.
Ferrous metal (of any shape) can concentrate magnetic fields, and this has been known to give
an unexpected increase in range. On the other hand, it can also concentrate interference sig-
nals towards a reader. What you should be on the lookout for is a situation where a relatively
long and thin ferrous metal structure has one end close to the antenna loop.
the effects of metal to advantage.
Metal close to an aerial loop can act as a short circuit, sucking energy out of the reader. It will
affect the tuning of the antenna, but even if the antenna is returned there could still be a loss of
range. The reading zone will change its shape, with the range behind the metal reduced.
The effect on the reading range is greater when the metal is closer to the antenna loop. Many
factors affect the range, but typically a complete sheet of metal, 100 mm (4 inches) behind the
antenna loop, reduces the reading range by about 25%. (If the metal is ferrous, it will have
slightly more effect.) This is after the antenna loop has been retuned.
When the metal is only close to part of the loop, the effect is reduced. If the metal is only close
to one side of the loop the effect is minimal.
As metal affects tuning, metal doors can pose a problem. If the antenna loop is too close, it’s
tuning will change when the doors are open. If the tuning is optimised when the doors are open,
the range will drop when the doors close (or vice versa).
Ferrous metal (e.g. steel) introduces new considerations. A sheet of ferrous metal reduces the
reading range by more than non-ferrous metal. It also acts as a better screen, with the range
behind the metal reduced to around 50% of the range in front. The shape of the reading zone
behind the metal is distorted, making the region where tags will be read less predictable.
Ferrous metal (of any shape) can concentrate magnetic fields, and this has been known to give
an unexpected increase in range. On the other hand, it can also concentrate interference sig-
nals towards a reader. What you should be on the lookout for is a situation where a relatively
long and thin ferrous metal structure has one end close to the antenna loop.