small as desired for precise level or
distance control. A typical example of
precise level control is when the applica-
tion calls for maintaining a constant fill
level in a filler machine. In this example,
the analog output provides a means of
controlling the product flow into the filler
as the filler speed changes. The analog
output may provide a means for control-
ling the speed of other machinery as
well as regulate the movement of control
valve actuators. The analog output may
also connect directly to programmable
controller analog input modules for
performing complex loop control or
simple status (e.g., distance measuring)
monitoring functions. All control limits
are stored in nonvolatile memory and
thus are retained if power is removed
from the sensor.
Unlike other sensing technologies,
these sensors are capable of detecting
all materials, liquid, granular and solid,
regardless of color, shape and composi-
tion, transparent or opaque, including
powder, food products, grains, chemi-
cals, pharmaceuticals, oils, plastics and
objects that change colors. The
threaded housings are available in ether
ULTEM® plastic or SS303 stainless steel
which are epoxy encapsulated to with-
stand shock and vibration. Both hous-
ings are sealed to withstand dusty, dirty,
clean-in-place, noncondensing humidity,
high-pressure washdown environments
and they are virtually unaffected by
changing light conditions, colors and
noise. In meeting NEMA 4X and IP67
industry standards, the sensors resist
most acids, bases and oils, including
most food products. All the sensors in
this model series are CE certified.
1-meter- and 2-meter-
span models
For purpose of definition, the standard
1-meter-span models are identified in the
Model Reference Guide as the Model
SM906A-1 and SM956A-1 series sensors
and the 2-meter-span models are
identified as the Model SM906A-4 and
SM956A-4 series sensors. Respectively,
these models provide for analog output
sensing from 50.8 mm to 1 m (2 to 39")
and 120 mm to 2 m (4.7 to 79"). The 96
mm (3.78") length of the connector model,
excluding the connector/cable assembly,
adds to the sensor’s installation conve-
nience. Operating on a sonic frequency of
200 kHz, these sensors have a standard
response time of 25 ms and 35 ms for the
1- and 2-meter-span models, respectively
with others available as shown in the
Model Reference Guide. The FDA
approved silicone rubber transducer,
while used to couple the ultrasonic
energy to the air, is also resistant to most
acids, bases and oils and food products.
Selected 1- and 2-meter-span sensors
have DeviceNet capability.
Various functional choices plus the
mounting convenience of a 30 mm
housing combine to achieve reliability
and cost effectiveness for these models in
the detection of moving object positions
in specific sensing applications. These
include: monitoring and controlling levels
of liquids and solid materials in bins and
filler bowls, controlling container flow on
mass conveyors, monitoring and control-
ling roll diameters and speeds, webs of
paper and fabrics, extrusion widths,
tension, dancer loops and valve posi-
tions, as well as the modulation of
variable-speed motors, pumps and
winding/unwinding equipment.
For 1-meter-span, analog-output
sensing applications that require mea-
surement and control capability in severe,
corrosive-type environments, the Model
SM906A-7STS and Model SM956A-7STS
series models have an SS303 stainless
steel housing and an SS304 stainless
steel-faced transducer. With an analog
sensing span of 120 mm to 1 m (4.7 to
39"), these sensors provide reliable
operation in either the detection of certain
chemicals and corrosive materials or
where caustic cleaning solutions are used
in washdowns of machinery and equip-
ment in close proximity to the sensor. For
out-of-doors, analog-sensing applica-
tions, where cold weather is a factor, this
corrosion-resistant model series provides
reliable operation in temperatures as low
as -10° C (14° F).
8-meter,
long-span models
The Model SM906A-8 and Model
SM956A-8 series represents the only
analog sensors on the market that offers
the combination of shortest deadband,
longest span and smallest package. As
indicated in the Model Reference Guide,
these sensors measure and monitor the
position and level of objects over a
sensing span of just 203 mm (8") to 8 m
(26'). With this shortest dead- band, the
need to position the sensor at great
distances from the object, typical of
most long-span sensors, is eliminated.
At only 116.31 mm (4.579") in length for
the cable-style model, a fraction of the
size of other long-span sensors, these
30 mm diameter sensors are easily
mounted in covers and other tight
spaces in the plant. They operate on a
sonic frequency of 75 kHz with a
standard response time of 250 ms and a
minimum response time of 150 ms. Other
response times are available. An epoxy
transducer face, in addition to coupling
the ultrasonic energy to the air, allows the
sensor to perform in a wide range of
harsh environments including those
involving most acids, bases and oils.
By virtue of the 75 kHz frequency,
the sensor’s wide, 20-degree beam is
especially effective in sensing the tank
or bin levels of various types of liquids,
solids and granules. This includes
applications involving the blending of
ingredients and the processing of food
products and pharmaceuticals, as well as
the treatment of water and sewage. For
outdoor analog output applications, the
sensors have temperature compensation
for operation in temperatures ranging
from -20° to 60° C (-4° to 140° F). In
applications where high sound absorp-
tion conditions exist in the material being
detected, (e.g., tiny plastic pellets), and
either the 1- or 2-meter span model
sensor becomes unreliable because of
lost energy, the more powerful long-span
SM906 can provide the solution when
used in the shorter-span distances.
Operation
The SUPERPROX® Model SM906
series is a self-contained, pulse-echo
device that both transmits and receives
sonic energy within the specified analog
span. Operating on 15 to 24 VDC, these
sensors use the latest ultrasonic sensing
and microprocessor technology that
allows the sensor to ignore all surround-
ing sonic interference and detect only
the designated object.
During operation, the sensor monitors
the distance to an object or level while
generating a proportional analog output
relative to the two analog span limits.
When an object is within the analog
span, the analog output value changes
proportionally in relation to the analog
span limits. For example, if the object is
half way between the analog span limits,
the output is either 5 Volts or 12 mA,
depending on the output model se-
lected. The output range adjusts to the
size of the analog span and remains
proportional regardless of where the
limits are set for the analog span.
The sensors are equipped with a
multicolor sensing status LED and a red
output LED. The multicolor LED indicates
where the level or target position is
relative to the span limits. It is green
when the object is between the analog
span limits, red if closer than the near
span limit, and amber if farther than the
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