SCXL-MaxSonar
®
- WRS
™
Series
SCXL-MaxSonar - WRS Series
Self-Cleaning, High Resolution, IP67 Weather Resistant
Ultrasonic Snow Depth Sensor
MB7534, MB7544, MB7554, MB7564, MB7574, MB7584
5
®
™
The SCXL-MaxSonar-WRS sensor line is optimized for ‘soft acoustic’ targets such as snow and includes an effective
self-cleaning capability designed to reduce the impact of condensation in closed or high-moisture (dew, frost, etc.)
environments providing high accuracy and high resolution ultrasonic proximity detection and ranging in air, with an
IP67 weather resistant rating. This sensor line features 1-mm resolution, target-size and operating-voltage
compensation for improved accuracy, superior rejection of outside noise sources, internal speed of sound
temperature compensation and optional external speed-of-sound temperature compensation. The SCXL MaxSonar-
WRS self-cleaning sensors have a maximum range of 5-meters. This ultrasonic sensor ranges to objects from 50-cm
to maximum range. Objects closer than 50-cm are typically reported as 50-cm. The interface output formats are
pulse width, analog voltage, and digital serial in either RS232 or TTL. Factory calibration is standard.
Precision Ultrasonic Range
Sensing
•
Self-cleaning algorithm runs during
normal operation
•
Range-finding at a fraction of the
cost of other precision rangefinders
•
Reading-to-reading stability of
1-mm at 1-meter is typical
1
•
Accuracy is factory-matched
providing a typical accuracy of 1%
or better
1,2
•
Compensation provided for target
size variation and operating voltage
range
•
Determines range to first detectable
object
•
Internal temperature compensation
is standard & optional external
temperature compensation
•
Excellent clutter rejection
•
Additional chemical resistance
available
3
•
Serial, 1-mm resolution
•
Available in RS232 or TTL
•
Operating voltage from
Range Outputs
•
Pulse width, 1uS/mm resolution
•
Analog Voltage, 5-mm resolution
2.7V to 5.5V
4
Easy to use Component Module
•
IP67 Rated
•
Stable and reliable range readings and
•
Best operated at 5V for snow
excellent noise rejection make the sensor applications
easy to use for most users
•
Current draw of ~34mA at 3.3V, and
•
Easy to use interface with distance
~68mA at 5V
provided in a variety of outputs
•
Sensor should remain on and be
•
Target size compensation provides
allowed to free run for self-clean
greater consistency and accuracy
feature to operate
•
Sensor automatically handles acoustic
Applications & Uses
noise
1,2
•
Weather station monitoring
•
Small and easy to mount
•
Calibrated sensor eliminates most sensor
•
Snow level measurement
(MB7554, MB7574)
to sensor variations
•
Bin level measurement
General Characteristics
•
Corn level measurement
•
Low cost ultrasonic rangefinder
•
People detection
•
Detection out to 5-meters
Notes:
1
Users are encouraged to evaluate the sensor
•
Resolution of 1-mm
performance in their application
•
Distance sensor from 50-cm to 5-meters
2
by design
•
Excellent
1
Mean Time Between Failure
3
F-Option provides additional protection from
hazardous chemical environments
4
(MTBF)
Please reference page 3 for minimum operating
voltage verses temperature information
•
Operating temperature range from -40°C
5
Please reference page 16 for part number key.
to +65°C
4
Close Range Operation
Applications requiring 100% reading-to-reading reliability should not use MaxSonar sensors at a distance closer than
50cm. Although most users find MaxSonar sensors to work reliably from 0 to 50cm for detecting objects in many
applications, MaxBotix
®
Inc. does not guarantee operational reliability for objects closer than the minimum reported
distance. Because of ultrasonic physics, these sensors are unable to achieve 100% reliability at close distances.
_______________________________________________________________________________________________________________________________________
Warning: Personal Safety Applications
We do not recommend or endorse this product be used as a component in any personal safety applications. This product is
not designed, intended or authorized for such use. These sensors and controls do not include the self-checking redundant
circuitry needed for such use. Such unauthorized use may create a failure of the MaxBotix
®
Inc. product which may result
in personal injury or death. MaxBotix
®
Inc. will not be held liable for unauthorized use of this component.
MaxBotix
®
Inc.
Copyright 2005 - 2012 MaxBotix Incorporated
Patent 7,679,996
MaxBotix Inc., products are engineered and assembled in the USA.
Page 1
Web:
www.maxbotix.com
PD12673d
SCXL-MaxSonar
®
- WRS
™
Series
SCXL-MaxSonar-WR Pin Out
Pin 1- Temperature Sensor Connection:
Leave this pin unconnected if an external temperature sensor is not used. For
best accuracy, this pin is optionally connected to the HR-MaxTemp temperature sensor. Some additional information for
the temperature sensor can be found on page 8 of the datasheet.
Pin 2- Pulse Width Output:
This pin outputs a pulse width representation of the distance with a scale factor of 1uS per
mm. The pulse width output is sent with a value within 0.5% of the serial output.
Pin 3- Analog Voltage Output:
This pin outputs a single ended analog voltage scaled representation of the distance.
This output is referenced to the sensor ground and Vcc. After the ~50mS power up initialization, the voltage on this pin
is set to a low voltage. Once the sensor has completed a range reading the voltage on this pin is set to the voltage corre-
sponding to the latest measured distance.
The SCXL-MaxSonar-WRS self-cleaning sensors use a scale factor of (Vcc/5120) per 1-mm. The distance is output with
a 5-mm resolution. The analog voltage output is typically within ±5-mm of the serial output.
Using a 10-bit analog to digital converter with the SCXL-MaxSonar-WRS self-cleaning sensors, one can read the analog
voltage counts (i.e. 0 to 1023) directly and just multiply the number of counts in the value by 5 to yield the range in mm.
For example, a converted value of 60 corresponds to 300-mm (where 60 x 5 = 300), and 1000 counts corresponds to
5,000-mm (where 1000 x 5 = 5,000-mm).
Pin 4- Ranging Start/Stop:
This pin is internally pulled high. If this pin is left unconnected or held high, the sensor will
continually measure and output the range data. If held low, the SCXL-MaxSonar-WRS self-cleaning sensors will stop
ranging. Bring high for 20uS or longer to command a range reading.
Pin 5-Serial Output:
The MB7534, MB7554, and MB7564 sensors have an RS232 data format (with 0V to Vcc levels)
and the MB7544, MB7574, and MB7584 sensors have a TTL outputs. The output is an ASCII capital “R”, followed by
four ASCII character digits representing the range in millimeters, followed by a carriage return (ASCII 13). The maxi-
mum range reported is 4999 mm. A range value of 5000 corresponds to no target being detected in the field of view.
The serial data format is 9600 baud, 8 data bits, no parity, with one stop bit (9600-8-N-1).
Because the data is presented in a binary data format, the serial output is most accurate.
V+ Pin 6 -
Positive Power, Vcc: The sensor operates on voltages from 2.7V - 5.5V DC. The SCXL-MaxSonar-WRS self
-cleaning sensors have a current draw of ~34mA at 3.3V and ~68mA at 5V. For best operation, the sensor requires that
the DC power be free from electrical noise. (For installations with known dirty electrical power, a 100uF capacitor placed
at the sensor pins between V+ and GND will typically correct the electrical noise.) Please reference page 3 for minimum
operating voltage verses temperature information.
GND Pin 7 –
Sensor ground pin: DC return, and circuit common ground.
MaxBotix
®
Inc.
Copyright 2005 - 2012 MaxBotix Incorporated
Patent 7,679,996
MaxBotix Inc., products are engineered and assembled in the USA.
Page 2
Web:
www.maxbotix.com
PD12673d
SCXL-MaxSonar
®
- WRS
™
Series
About Ultrasonic Sensors
The SCXL-MaxSonar-WRS self-cleaning ultrasonic sensors are in-air, non-contact object detection and ranging sensors
that detect objects within an area. These sensors are not affected by the color or other visual characteristics of the detected
object. Ultrasonic sensors use high frequency sound to detect and localize objects in a variety of environments. Ultrasonic
sensors measure the time of flight for sound that has been transmitted to and reflected back from nearby objects. Based
upon the time of flight, the sensor outputs a range reading.
_______________________________________________________________________________________________________________________________________
SCXL-MaxSonar-WRS
The SCXL-MaxSonar-WRS self-cleaning sensor is a low-cost, rugged ultrasonic snow depth sensor that is optimized for
reliable snow depth measurement. Internally, multiple sensor readings are analyzed using algorithms optimized for snow
measurement, ensuring accurate snow depth measurements. The sensor accurately applies temperature compensation to
every reading, using either the integrated temperature sensor or the optional external temperature sensor (HR-MaxTemp).
_______________________________________________________________________________________________________________________________________
SCXL-MaxSonar-WRS Mechanical Dimensions
_______________________________________________________________________________________________________________________________________
Voltage vs Temperature
The graph below shows minimum operating voltage of the sensor verses temperature.
MaxBotix
®
Inc.
Copyright 2005 - 2012 MaxBotix Incorporated
Patent 7,679,996
MaxBotix Inc., products are engineered and assembled in the USA.
Page 3
Web:
www.maxbotix.com
PD12673d
SCXL-MaxSonar
®
- WRS
™
Series
Self-Cleaning Description
The SCXL-MaxSonar-WR sensors feature a self-cleaning protocol which gently heats the face of the transducer, and
atomizes any moisture/condensation on the sensor’s transducer face. This feature allows the sensor to be used in a wide
variety of applications that may experience condensation issues. Self-cleaning is needed for many such applications due
to detection performance limitations resulting from condensation, including only reporting the minimum or maximum
reported distance.
Condensation is frequently an issue in tanks because the sensor is typically mounted at the top of the tank, above a
warmer liquid. On clear nights or cold nights, this causes the sensor hardware to be colder than its surrounding
environment, causing condensation to build up on the surface of the exposed sensor hardware. This can also occur in
some buildings, depending on climate control.
The reason that condensation is problematic to sensors is fairly straightforward. Sensors determine distance to targets,
even if that target is on the surface of the transducer. Targets (condensation, solid particles, etc.) on the surface of the
transducer impede sensor operation. These targets (on the surface of the transducer) will either be detected or cause a
reduction in the sensitivity of the sensor. The self-cleaning operation is designed to prevent buildup and remove buildup
of moisture from the surface of the transducer. For proper self-cleaning, the sensor must remain on, and continue normal
ranging operation.
The self-cleaning feature is only designed for moisture, not removal of dust or other solid particles. Multiple sensor
operation is not possible without running in triggered mode.
Single-sensor operation
The self-cleaning protocol runs with the RX pin is set to ‘High’. It does not run with the RX pin is set to ‘Low’. We
recommend running this protocol when condensation is expected. This will occur at different times depending on your
specific application environment. Sensor wiring for single sensor operation is shown on page 9 of this datasheet.
Multiple-sensor operation
Running more than one sensor in a given environment is only possible by running in triggered operation mode.
Below are several different strategies for setting up multiple sensors in triggered mode (arranged in order for use in
lower-moisture to higher-moisture environments).
1.) (Note: this low-power strategy maximizes sensor availability while allowing self-cleaning cycle to run – for
lower-moisture environments, or where maximum data is needed):
a. Run each sensor for seven (7) seconds in sequence. Take a range reading from each sensor sequentially.
2.) (Note: This strategy is designed for high-moisture environments, saves battery when condensation is not expected. For
example, during the portion of the night when the temperature is dropping):
a. Run all sensors continually when condensation is expected.
b. Only run a sensor when range information is needed. At this time, shut down (by holding the RX pin LOW) all
the other sensors and cycle the desired sensor for seven (7) seconds.
c. Timing of sensor cycles should be based on other data (i.e. time of day/year, temperature, etc.)
3.) (Note: This strategy maximizes self-cleaning cycles over time - for high-moisture environments):
a. Run all sensors continually while ignoring range output (keeps sensors condensation-free but no range readings
during this time – maximizes self-cleaning cycles over time)
b. When a reading is desired, shut down the sensors, trigger each individual sensor one at a time for seven (7)
seconds and take a range reading for each sensor
c. Go back to step 1 (keep all sensors running).
MaxBotix recommends choosing an SCXL-MaxSonar-WR product for applications that are in high-moisture
environments, or which are vulnerable to occasional condensation. These sensors are IP67 rated, so water or ice will not
damage the sensor. However, water or ice on the transducer surface will impede the sensitivity of the sensor, as outlined
above.
MaxBotix
®
Inc.
Copyright 2005 - 2012 MaxBotix Incorporated
Patent 7,679,996
MaxBotix Inc., products are engineered and assembled in the USA.
Page 4
Web:
www.maxbotix.com
PD12673d
SCXL-MaxSonar
®
- WRS
™
Series
Sensor Mounting
It is recommended that several factors be taken into account when using the SCXL-MaxSonar-WRS self-cleaning
ultrasonic snow depth sensors.
Due to the high gain of the sensor, the first recommendation is to mount the sensor far enough away from any supporting
masts or towers. For a mast that is 5 meters high (or higher) the sensor should be mounted at least 100cm away from the
mast. For a mast that is 2.5 meters high (or lower) the sensor should be at least 75cm away from the mast. (This
corresponds to a mounting clearance angle of
≥11.3
degrees)
For users desiring the highest accuracy, it is recommended to use a properly mounted external temperature sensor.
MaxBotix Inc., is developing several components to assist in high accuracy readings and protection of the
SCXL-MaxSonar-WRS self-cleaning sensor and HR-MaxTemp sensor.
The first component is a shroud that is assembled over the top of the SCXL-MaxSonar-WRS self-cleaning sensor housing,
figure 1. This shroud is a UV shield for the sensor. The shroud is also acts to protect the sensor from hail, heavy snow,
and snow build up.
The second component is a louver design housing to protect the temperature sensor from direct and reflective UV rays,
figure 2. This housing has been created to maintain a real time accurate temperature. This component is separate from
the shroud that covers the SCXL-MaxSonar-WRS self-cleaning sensor.
The third component is a fan housing which holds either an AC or DC cooling fan under the temperature housing, see
figure 3. This has been created for maximum airflow to the temperature sensor housing. The fan housing helps to ensure
the temperature sensor is the same temperature as the surrounding environment.
All the components listed above are designed to use standard hardware for mounting to new or existing weather stations
or other mounting components.
Figure 4 shows the recommended mounting for the SCXL-MaxSonar-WRS self-cleaning snow depth sensor with the
HR-MaxTemp temperature sensor.
Mounting information for the snow sensor can be found in the application note here: ww.maxbotix.com/articles/070.htm
Figure 1
Figure 2
Figure 3
Figure 4
MaxBotix
®
Inc.
Copyright 2005 - 2012 MaxBotix Incorporated
Patent 7,679,996
MaxBotix Inc., products are engineered and assembled in the USA.
Page 5
Web:
www.maxbotix.com
PD12673d
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