Jameco Part number 151482
151482 - Ultrasonic Sensor User's Guide
Performance
Update Rate
The sensor measures distance repetitively at an interval
of approximately 50 milliseconds. This is the interval
between the "clicks" heard from the transducer. After
each measurement, the 3 characters of data are
transmitted on the RS-232 output.
Target Considerations
The target must reflect the ultrasound energy back to the
sensor. Sensor performance will be affected by the
strength of the "echo". Flat surfaces are best when
perpendicular to the beam direction. Curved surfaces are
generally good targets because a portion of the energy is
generally reflected directly back to the sensor.
Low-density materials including some foams, cloth and
powders may exhibit reduced detection range, or can
absorb or be transparent to ultrasound. In many cases
these materials are easily detected, so testing a material
sample is recommended. Increasing the sensor's gain
using the sensitivity adjustment may be required.
Temperature Effects
The most significant factor that affects measurement
accuracy is temperature. At room temperature, a change
of 10 degrees will result in approximately 1% change in
the speed of sound and therefore the same change in the
distance output. This model sensor does not compensate
for temperature affects.
Precautions
•
Keep unintended targets from transducer's field
of view. Keep the beam pattern in mind.
•
Keep transducer away from ultrasonic noise
sources, such as pressurized air nozzles
Adjustments
Sensitivity
This adjusts the electronic sensitivity to the strength of
the ultrasonic echo being returned from the target object.
Very small or sound absorbing targets may not send a
very strong echo and therefore may require increased
sensitivity for stable detection. The sensitivity
potentiometer is located next to the terminal block on the
solder side of the circuit board. The unit is shipped at
mid range and in general it does not require adjustment.
Sensitivity can be increased by rotating the potentiometer
clockwise and decreased by counterclockwise rotation.
Full rotation of the pot is 180 degrees.
Ultrasonic Tuning Adjustments
The ultrasonic tuning adjustments consist of a
transformer T1 (silver case) and inductor L1. These
generally do not require adjustment unless the cable
length to the transducer is lengthened.
To adjust these components:
1. Put an oscilloscope probe on test point TP1 and
set the scope to trigger on the transmitted pulse.
This test point is a hole in the PCB that is
labeled on the component side of the board.
2. Using delayed sweep, monitor a target echo
signal and adjust T1 for maximum amplitude.
3. Using the same signal as in step 2, adjust L1 for
maximum amplitude.
Transducer Cable Length
As the cable length is increased, sensitivity will
decrease. A practical cable maximum length is
20 feet, and longer cables should be shielded in
electrically noisy areas.
Senix Corporation, 52 Maple St., Bristol, VT 05443
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