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DISTANCE / PROXIMITY
SENSORS |
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GENERAL
SPECIFICATIONS |
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The Microsonar range
of non-contact proximity devices consists of programmable
transmitter and switch models respectively. The
4-20 mA output current or 0-10 V output voltage
of the transmitters as well as the switch-in or
switch-out point of the switch models can be assigned
to any portion of the measuring range.
The 500 ohm maximum load resistance specified for
the 4-20 mA output of the transmitters complies
with the industrial standards. A high output sink-current
of the 200 mA switch units enable the Microsonar
to drive power relays directly. |
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APPLICATION |
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The primary application
field of the Microsonars is the factory automatisation.
These proximity transmitters and switches are applicable
to detect objects or measure the distance of objects
from the proximity device. The objects to be detected
or those we wish to measure the distance from the
Microsonar must be having a surface parallel to
their transmitting-sensing membrane and featuring
good acoustic reflection properties. The surface
unevenness and the irregular shape of the objects
does not necessarily prohibit their sensing, such
a feature is however to be counted with as a range
limiting factor.
A range reduction is to be expected by sensing cylindrical,
spherical objects. The Microsonars can be used to
the position sensing of machine parts, small vehicles,
trolleys, forklifts, cranes. They can also be used
on packaging, sorting or machining equipment in
case the objects handled by this equipment have
reflection properties and their speed is within
specified limits. A basic condition of a troublefree
application is the vibration-free fixing of the
Microsonars on the carrier or on a stationary object.
There may be the need of using a de-coupling gasket
in special cases. |
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OPERATION |
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The operation of
the Microsonars is based on the reflection of the
sound. The distance is calculated by the microcomputer
incorporated in the Microsonar unit taking the elapsed
time between sending out an ultrasonic burst and
the reception of the reflected copy of it
Measuring distance samples taken as above can not
be always used because of interfering objects, the
moving of the air or because of other nonspecified
disturbances. To improve reliability of the measured
value the Microsonar 200 series of units perform
steps not commonly found in such low cost devices.
These processing steps include rejection of the
"unlikely" value and averaging those found "likely".
Another means to improve the reliability of the
measuring or detection is sample averaging. The
number of the samples used to compute the average
distance is programmable between 1 and 16.
Rejection of the samples or the computing the average
distance improves though reliability of the measured
value, but on the same token increases reaction
time. A fast reaction can only be expected in case
of good reflection and if the sound propagation
is undisturbed. |
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PROGRAMMING |
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The programming
of the Microsonars is different when performing
it on transmitters or on switches.
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TRANSMITTERS
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- Measuring range :0.2 -1m & 0.2 - 6m
- Distance corresponding to 4 mA or 0 V
- Distance corresponding to 20 mA or 10 V
- The begin of the Far-End Blocking Zone (the
distance over which we do not wish to measure)
- Number of samples used to compute the average
- The number of subsequent echoes we allow to
be lost
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SWITCHES |
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- Switch-on distance (the sink-current appears)
- Switch-off distance (the sink-current disappears)
- The begin of the Far-End Blocking Zone (the
distance over which we do not wish to detect)
- Number of samples used to compute the average
- The number of subsequent echoes we allow to
be lost
The programming can be performed two ways but always
using a Menu.
- Local programming (with magnet-touching)
Advancing in the menu is done by touching the
appropriate marking on the body of the Microsonar
by the magnet supplied.
- Remote programming (through the connecting
cable)
Electrical pulses are to be applied to the wire
named PRG. The simplest way to apply a pulse
is to touch PRG to the supply voltage (Us).
One can also use external switches or keys connected
between PRG and the supply voltage (Us) to perform
programming. Status indication is provided by
a three-colored LED.
Irrespectively of programming locally or remote
the storing of the distance parameters is done by
"teach in". A good reflecting surface is to be established
in front of the transmitting-sensing membrane of
the Microsonar followed by advancing to the appropriate
point of the Menu. The memory of the Microsonar
then stores the distance value and assigns it to
the parameter involved. |
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