Difference between revisions of "Snow height - ultra sonic sensor"

Revision as of 14:03, 7 October 2008

Parameter to be measured:

Snow height

Method:

Ultra sonic sensor

Equipment:

Ultra sonic distance sensor: e.g. Campbell Scientific SR50 or USH-8 from company Sommer

Logger: Campbell recommend their loggers. But it can be connected to other loggers, e.g. a DL2E from Delta-T

Advantages:

Continous measurement

Disadvantages:

Measurement principle: The velocity of an ultrasonic signal in air depeding on the air temperature. For an accurate measurement of the snow height the puls length wich is proportinal to the distance has to be calibrated by the airtemperature. Sensor Campell SR50 use an external temperatur sensor and calculate the temperature compensation in the Campell data logger. The Sommer USH-8 use an internal temperature compensation and outputs the already compensated snow height to any data logger.

Measuring during snow fall is quite dificult because every snow flake produce additional reflected ultrasonic pulses. High-end sensors like, Sommer or Campell, can handle such additional reflections and measure reliable also during snow fall.

Expensive high end sensors
While the sensor itself without control electronic is cheap (about 10$ for robotics) connecting it to a logger requires quite some knowledge about digital electronics and programming. The signal from the sensor is usually a puls with a length proportional to the distance. Therefore, the more expensive (> 1000$) sensors from scientific instrumentation companies are usually used.

Problems/Questions:

Starting a measuring cicle in the SR50 from the DL2E was difficult, because the pulse generated in the DL2E was too long. In the end a solution using a micro controller was found.

Links

Projects that used the above equipment

Other related web sites

References

@@ Line 14: / Line 14: @@
 ==Disadvantages:==
-*Expensive
+Measurement principle:
-*While the sensor itself without control electronic is cheap (about 10$ for [http://www.robot-electronics.co.uk/ robotics]) connecting it to a logger requires quite some knowledge about digital electronics and programming. The signal from the sensor is usually a puls with a length proportional to the distance. Therefore, the more expensive (about 1000$) sensors from scientific instrumentation companies are usually used
+The velocity of an ultrasonic signal in air depeding on the air temperature. For an accurate measurement of the snow height the puls length wich is proportinal to the distance has to be calibrated by the airtemperature. Sensor Campell SR50 use an external temperatur sensor and calculate the temperature compensation in the Campell data logger. The Sommer USH-8 use an internal temperature compensation and outputs the already compensated snow height to any data logger.
+Measuring during snow fall is quite dificult because every snow flake produce additional reflected ultrasonic pulses. High-end sensors like, Sommer or Campell, can handle such additional reflections and measure reliable also during snow fall.
+*Expensive high end sensors
+*While the sensor itself without control electronic is cheap (about 10$ for [http://www.robot-electronics.co.uk/ robotics]) connecting it to a logger requires quite some knowledge about digital electronics and programming. The signal from the sensor is usually a puls with a length proportional to the distance. Therefore, the more expensive (> 1000$) sensors from scientific instrumentation companies are usually used.
 ==Problems/Questions:==