SMB18UR BANNER ENGINEERING, SMB18UR Datasheet - Page 2
![Sensor Mounting Bracket](/photos/19/84/198409/4606677_sml.jpg)
SMB18UR
Manufacturer Part Number
SMB18UR
Description
Sensor Mounting Bracket
Manufacturer
BANNER ENGINEERING
Specifications of SMB18UR
Brand/series
SMB18 Series
Mounting Type
Base/Barrel
Primary Type
Bracket
For Use With
T18, S18, M18 And MINI-BEAM Sensors
WORLD BEAM
2
Ultrasonic sensors emit one or multiple pulses of ultrasonic energy, which travel through
the air at the speed of sound. A portion of this energy reflects off the target and travels
back to the sensor. The sensor measures the total time required for the energy to reach
the target and return to the sensor. The distance to the object is then calculated using
the following formula:
To improve accuracy, an ultrasonic sensor may average the results of several pulses
before outputting a new value.
Temperature Effects
The speed of sound is dependent upon the composition, pressure and temperature of
the gas in which it is traveling. For most ultrasonic applications, the composition and
pressure of the gas are relatively fixed, while the temperature may fluctuate.
In air, the speed of sound varies with temperature according to the following
approximation:
Or, in English units:
Temperature Compensation
Changes in air temperature affect the speed of sound, which in turn affects the distance
reading measured by the sensor. An increase in air temperature shifts both sensing
window limits closer to the sensor. Conversely, a decrease in air temperature shifts both
limits farther away from the sensor. This shift is approximately 3.5% of the limit distance
for a 20° C change in temperature.
The QS18U series ultrasonic sensors are temperature compensated. This reduces the
error due to temperature by about 90%. The sensor will maintain its window limits to
within 1.8% over the -20° to +60° C range.
NOTES:
• E xposure to direct sunlight can affect the sensor’s ability to accurately compensate for
• I f the sensor is measuring across a temperature gradient, the compensation will be less
• T he temperature warmup drift upon power-up is less than 7% of the sensing distance.
After 5 minutes, the apparent switchpoint will be within 0.6% of the actual position. After
25 minutes, the sensing position will be stable.
changes in temperature.
effective.
P/N 119287 rev. E
C
C
m/s
ft/s
= 49 √460 + T
= 20 √273 + T
D = c t
®
2
QS18U Series Ultrasonic Sensors
F
C
Principles of Operation
C
T
D = distance from the sensor to the target
c = speed of sound in air
t = transit time for the ultrasonic pulse
C
T
F
ft/s
C
m/s
= temperature in °F
= temperature in °C
= speed of sound in feet per second
= speed of sound in meters per second
Banner Engineering Corp. • Minneapolis, MN U.S.A
www.bannerengineering.com • Tel: 763.544.3164