Banner U-GAGE ULTRA-BEAM Series - Manual (Page 4)

ULTRASONIC SENSING WITH BANNER "923" SERIES ULTRA-BEAMS
Analog output increases as distance to target
object increases. Near and far distances of
sensing window are set by NULL and SPAN
controls, respectively. The sloping line
represents the sensing window. Analog
output is linear within the window.
ADJUSTMENT OF "923" SERIES SENSORS
Installation and adjustment of "923" series ULTRA-BEAMs is per-
formed as described below. Some means of monitoring the ULTRA-
BEAM's analog output(s) is necessary. This can be done either by the
"final device" in the application or by a voltmeter or milliammeter con-
nected as shown in figures J, K, L, & M.
1) Choose either voltage sourcing or current sinking output, and
either positive slope or negative slope. The choice of sourcing or
sinking output will depend upon the input requirements of the instru-
ment that the ULTRA-BEAM will be connected to.
The choice of positive or negative slope will depend upon the require-
ments of the "final device" used and the "direction" of the "action" that
the analog output is to control or monitor. Positive slope analog output
(figure E) increases with increasing distance to the target object;
negative slope analog output (figure F) decreases with increasing
distance to the target object. The maximum and minimum output levels,
when set, will define the sensing window: the sourcing output range is
0 to +10V dc; the sinking output range is 0 to 20mA dc. The sensor's
analog output is linear within these ranges.
Refer to the Dimension Drawing (p. 2) and figure G. Disconnect
power from the sensor. Remove the front panel of the sensor by
removing the four mounting screws at the four corners of the rear panel.
Set the sensor for POSITIVE or NEGATIVE slope by positioning the
jumper clip on the POS/NEG SLOPE SWITCH behind the front panel
in the appropriate position. Replace the panel.
2) Determine where the ULTRA-BEAM will be mounted and the
proper position and "depth" of the sensing window.
Best results will be obtained when the ULTRA-BEAM is adjusted
when mounted in the actual sensing position, and when "looking" at the
actual material to be sensed. Mount the ULTRA-BEAM firmly and
securely in a location as free as possible from spray, dust, and dirt, but
which still allows reliable sensing. (Consider use of the Banner model
SMB900 mounting bracket.)
Note: if adjusting the ULTRA-BEAM in the actual "sensing position" is
not possible, "window" adjustments may be performed elsewhere. For
best results, use a sample of the actual material to be sensed as the target
(observe minimum target size requirement), and then move the sensor
to its final position. More than one adjustment attempt may be
necessary using this method. As a third alternative, use a smooth, flat
target.
The window must include within its boundaries the closest and farthest
positions (or levels) of the object(s) to be sensed. Allow for environ-
mental effects, if anticipated. Whenever possible, set up the sensing
window so that the object(s) will pass as nearly as possible through its
center. Also, make sure that the window is adjusted to ignore objects
beyond the target object(s).
FIGURE E. POSITIVE SLOPE ANALOG OUTPUT
In simplest terms, ULTRA-BEAM ultrasonic sensors operate by trans-
mitting ultrasonic sound pulses of a specific frequency (inaudible to the
ear) and, in between the transmitted pulses, listening for reflected pulses
("echoes") of the same frequency from an object in the path of the
ultrasonic beam. The sensor "knows" the speed of ultrasound and
measures the time lapse between the transmitted ultrasonic pulses and
the reflected echoes. The result is an analog output which represents the
distance from the sensor to the reflecting object. If the distance between
the sensor and the object changes, the ULTRA-BEAM sees a change in
the time lapse and, within 100 milliseconds, updates and puts out new
analog values. "923" series analog ultrasonic sensors can not only
detect the presence of an object, but also give a continuous indication
of the object's position along the sensing axis. (Note: the receiver must
receive an "echo" in order to update its output. This echo usually is
produced by the objects being sensed. If the object is removed from the
sensing window, the next "update" echo may come from any object
within the sensor's beam pattern, either inside or outside the sensing
window.)
By means of the internal SLOPE SELECT jumper switch, ULTRA-
BEAM's analog outputs may be set to produce either a positive or
negative slope. When adjusted for positive slope, the ULTRA-BEAM's
analog outputs (both voltage sourcing and current sinking) increase as
the object being sensed moves away from the sensor along the sensing
axis (figure E).
Analog output decreases as distance to target object
increases. Near and far distances of sensing window
are set by SPAN and NULL controls, respectively. The
sloping line represents the sensing window. Analog
output is linear within the window.
When adjusted for negative slope, both analog outputs decrease as the
object moves away from the sensor along the sensing axis (figure F).
Figures E and F are typical responses for applications like fill level
sensing, position sensing, and web tensioning, where movement along
the sensing axis toward and away from the sensor must be monitored
and/or controlled.
Reliable distance sensing is possible for objects crossing the beam
pattern at right angles to the sensing axis. In both the positive and the
negative slope modes, an object moving along a path perpendicular to
the sensing axis will begin to produce an analog output as it enters the
sensor's pattern. Output will continue until the object moves out of the
ULTRA-BEAM's sensing pattern.
ULTRA-BEAM sensors may also be used to detect size differences in
objects that are moving past the sensor at right angles to the sensing
axis, as on a conveyor. It is best to think of the objects as being
differentiated by their distance from the sensor rather than by their
actual size. The surfaces of the objects being sensed must be presented
to the sensor in such a way that size differences in the objects are seen
as dimensional differences along the sensing axis. These distances can
be detected by the sensor as changing sensor-to-object distances from
one object to another, and can be differentiated by changes in the analog
output.
FIGURE F. NEGATIVE SLOPE ANALOG OUTPUT
Figure G: ULTRA-BEAM Slope Select Jumper Setting
Gently pull the black jumper to remove;
push it down onto appropriate two pins.
JUMPER
JUMPER
NEAR
NEAR
FAR
FAR
Positive slope:
Negative slope: