DIY Instrument Shield

An instrument shelter provides a flow of air around weather sensors while protecting them from direct sunlight and rain. Without a shield, the sun can heat the temperature sensor giving a false high-temperature reading.

Professional weather stations use a large louvered box called a Stevenson Screen that is built to specific dimensions for standardized weather measurements. Smaller plastic shields can cost $100 or more. My station uses an AcuRite Radiation Shield that sometimes sells for as little as $10. Making your own instrument shelter can be an easy and fun project that may cost less than $6.

These instructions will give you a general idea how to build a shield. You can easily adapt the design to the materials you can find. The basic item is a shallow dish with nearly vertical straight sides. Dishes made as plant saucers are an excellent choice. The dishes are stacked on top of each other separated by beads and held together by wire ties. It makes a surprisingly sturdy design.

Here are suggested items. Any reasonable substitute will work if you can’t find these exact items:
• 4-in Clear Plastic Plant Saucer – Buy six and maybe a few spares.
• White Spray Paint
• Nylon Wire Ties – 6 to 11-inches long – Harbor Freight $2.00
• Plastic or wood craft beads of the “large hole” variety. They are often called pony beads. The hole must be large enough to allow the wire tie to pass through – Dollar Tree or Walmart.

You need to have at least six small saucers with flat bottoms and steep shallow sides. Plant saucers of 4 to 6-inch inch (100 mm – 150 mm) diameter work well. Plant saucers are very thin so larger saucers are not strong enough. Paint them white with spray paint inside and out.

After the paint is dry, cut a hole in the flat bottom of five of the saucers leaving a ring at least 1/4-inch (6 mm) wide. The sixth uncut saucer will be the top of the shield. The holes should be a little larger than the width of the weather station printed circuit board, say 1.75-inches (45 mm). Cut three small slots wide enough to pass the tail of a wire tie in the flat bottom ring of each saucer. The slots must all line up. One way to do this is to make three equally spaced guide marks on the top saucer with a permanent marker. Place each of the other saucers over the top one and put marks in the same places. You can see the guide marks by holding them up to a light. Cut short slots at all the marks with a craft knife.

Look at how wire ties work: one side of the tail is smooth, the other side has ridges that engage with a tongue in the head of the tie.

Place the tail of a wire tie through each of the slots in the top saucer with the ridged side facing the center of the saucer hole. Put enough beads over the tails of the wire ties coming out the other side of the saucer so that they stack up to about half the depth of a saucer. Thread the ties through the holes in the next saucer. Do this for each saucer.

You should now have a loose stack of saucers with three wire ties sticking out the bottom. Place a bead on each of the wire ties to act as a washer, then carefully press the head of another wire tie over each tail. You can tighten these up by hand to hold the stack firmly together. The tails of the new wire ties will cross more-or-less in the center of the bottom saucer. Cut three small slots in the side of the bottom saucer opposite from each wire tie. You can gently pry up the tails and insert the LiPo cell and weather station PCB into the hole with the solar cell outside. Pass the tails through the slots to secure the weather station in the shield.

Mounting the station is up to you. One possibility is to pass wire tie tails through the heads in the top of the shield and fasten them to some convenient bracket. For a few dollars more, buy a set of magnetic hooks like the ones Harbor Freight sells as item # 98502. Before you put your station inside the shield, drop a 1-1/2-inch (40 mm) steel (not stainless) washer into the shield. Place the magnetic hook on the other side so that it attracts the washer.

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