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Agronomy Journal Abstract -

Speedometer for Operator-Propelled Equipment


This article in AJ

  1. Vol. 83 No. 3, p. 647-649
    Received: June 4, 1990

    * Corresponding author(s):
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  1. D. D. Wolf ,
  2. L. D. Wolf and
  3. D. J. Parrish
  1. D ep. of Crop and Soil Environmental Sciences, Virginia Tech
    E merson Electric Co., Electronics and Space Div.
    D ep. of Crop and Soil Environmental Sciences, Virginia Tech.



Accurate delivery of solutions from a sprayer or of seed and fertilizer from ground-driven spinner spreaders requires accurate travel speeds. The objective of this note is to provide plans for building your own inexpensive electronic speedometer. Where the applicator is mounted on wheels, an accurate speed can be maintained using a computerized bicycle speed indicator and small magnets secured at equal intervals around the spokes. Insulated wire connects the magnetic sensor to a computerized digital display unit mounted within view of the operator. The computerized display is calibrated for the diameter of the wheel by settings in the operator's manual. The indicated speed is 10 times the actual speed. Speed is updated each second and displayed to the nearest 0.1 km h−1. The computer unit and materials can be purchased from local suppliers and assembled in a few hours. Evaluation of performance was made by four subjects under several conditions. When considering subjects and conditions, the standard error of travel speed was 0.056 km h−1 when operating the unit at a target of 3.22 km h−1 (2.0 MPH). This means that a range of 3.16 to 3.28 km h−1 could be achieved 95% of the time while intending to travel at 3.22 km h−1.

Contribution from the Dep. of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.

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