How to Build a Professional Rain Gauge
Meteorologists use a rain gauge for measurement of precipitation in a region. A rain gauge is a device that collects precipitation and provides accurate measurements of how many millimeters of rain has fallen. It is a simple device consisting of a funnel that collects water into a calibrated cylinder. You can construct a professional-style rain gauge to measure precipitation. Measuring rainfall is useful for determination of watering requirements for any lawn, garden and farm crops. Accurate measurements of precipitation could help determine needs for additional watering. Does this Spark an idea?
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Things You'll Need
- Large, plastic long-stem funnel
- Plastic graduated cylinder, 100 ml
- Wide-mouth plastic jar, 1 gallon
- Flexible plastic ruler with mm measurements
- Coffee filter, cone shaped
- Rubber bands
Instructions
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1
Measure diameter (d1) of the funnel opening to determine rain collection area. The area can be calculated using the formula 3.14x (d1/2)squared.
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2
Measure the diameter (d2) of the graduated cylinder. The area is determined using the formula 3.14(d2/2)squared. Because the opening of the graduated cylinder is less than the funnel, it is necessary to multiply mm of rain collected in the cylinder by a conversion factor. This conversion is determined using the formula cylinder area/ funnel area. An example would be a 0.25 times conversion for as funnel area of 120 for the cylinder/ 480 for the funnel.
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3
Attach the ruler to the graduated cylinder. The zero measurement should be flush (even) with the inside bottom of the cylinder for most accurate measurements. The flexible plastic ruler can be wrapped around the cylinder and attached with rubber bands. Tape can also be used but could become loose when wet.
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4
Insert the graduated cylinder into the center of the plastic jar. The jar should be slightly taller than the cylinder. The jar will act as an overflow container and provide a support to hold the funnel.
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5
Insert the funnel into the jar with the stem inserted into the cylinder. The stem will help support the graduated cylinder.
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6
Place the coffee filter inside the funnel. The filter will prevent dirt and other debris from collecting in the graduated cylinder. Coffee filters are advantageous because they absorb very little moisture and would not affect the accuracy of measurements. The rain gauge is now ready to use.
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Place the rain gauge in a clear area free from overhead obstacles. The rain gauge could be placed in a small hole in the ground where it is supported and will not tip over. It can also be attached to a fence post or pole with wire.
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Tips & Warnings
A larger graduated cylinder, 250 ml, can be used in areas where there is substantial rainfall. It is also possible to substitute a plastic jar using a 2-liter soda pop bottle with the top cut of or a plastic pitcher.
Plastic is the preferred material for constructing a rain gauge. Debris on windy days could crack or break glass if it is used. Professional rain gauges are made from plastic. It is also important to note that a rain gauge measures rain and not snow or other frozen precipitation. It is a limit of the rain gauge device.
References
Resources
- Photo Credit rain drops image by Stephen Orsillo from Fotolia.com
