This method for constructing a low-cost radiation shield can help improve air temperature measurements in ecological field studies. The main advantage of this technique is the small size of the shield which reduces construction cost to less than half that of similar models and makes your instruments less conspicuous in the field. To construct a radiation shield use a utility knife to cut corrugated plastic sheets into one 15 centimeter and two 10 centimeter squares.
For the top layer of the small radiation shield, use a pencil to draw a line four centimeters from one edge of the 15 centimeter square and use a straight edge as a guide to score along the line. Next, measure 3.8 centimeters from the edges perpendicular to the four centimeter line, and use the straight edge to score from the bottom of the square up to the four centimeter line. Then draw a line from both corners above the four centimeter line to the junction of the four centimeter and 3.8 centimeter lines, and cut along this line.
For the middle and bottom layers of the small radiation shield, use the straight edge to draw a six centimeter square in the middle of each 10 centimeter square, and score all around each six centimeter square, and from each corner of the six centimeter squares to the outer corners of the 10 centimeter squares. Now, fold the 15 centimeter sheet along the scored lines, and tuck the small triangular flaps on the inside of the larger back flap, securing temporarily with binder clips, and completely cover the scored side with aluminum foil tape. When the 15 centimeter square is folded correctly, the cut edge of the back flap will be flush with the folded sides, and the entire convex surface will be taped.
Then use aluminum foil tape to completely cover the scored side of one of the 10 centimeter squares, and the unscored side of the other 10 centimeter square. Using a 1/4 inch drill bit, drill holes in each of the shields'layers, and run a cable tie through the eyelet of the censor housing and through the holes of the underside of the 10 centimeter square that is taped on the scored side and has the two holes drilled into the middle. Pinch the sides of each 10 centimeter square along its diagonal scored lines, using a heavy duty stapler to hold the pinched sides together.
The end product will have a square bowl shape. When the second bowl is finished, thread a cable tie first through the left back hole of the 10 centimeter sheet taped on the unscored side. Then, through the left back hole of the second 10 centimeter sheet, leaving a two centimeter vertical space between the two sheets to allow airflow around the temperature censor.
Thread a cable through the back right holes in the same way, and pass a cable tie through the two side by side holes in the back left of the 15 centimeter square sheet. Attach this tie to the 10 centimeter sheets, leaving two centimeter of space between the 15 centimeter sheet and the top of the upper 10 centimeter sheet, and thread the two side by side holes in the back right of the 15 centimeter sheet in the same manner. For mounting, drill additional holes into the back end of the assembled product as necessary.
Then pass one cable tie through all three holes in the front of the sheets, and tighten the cable tie, taking care that the space is even between all three sheets. Ensure that the three sheets lay parallel to the ground when mounted. In this representative field experiment, positive biases were found across all four tested censors using the small radiation shield that were similar to those obtained using the original larger shield design, but were much less than the biases of the unshielded censors.
The small shields also resulted in the recording of some outlier warm temperatures relative to the original shield design, although the overall differences were small. Warm biases were strongest during periods of peak solar radiation, but in both the small and large shield cases, these biases were much less than the biases of the unshielded censors. The mean temperature differences between all of the combinations of censors outfitted with the small radiation shield compared to the original design, revealed that the largest differences occurred at 08:00 hours local time.
When constructing this shield, it's important to remember to completely cover each square with the reflective aluminum tape, to keep even spacing between the squares, and to mount the final constructed shield parallel to the ground. Measuring microclimatic variation in air temperature can help provide insights into local biological responses to recent and projected climate change. Using a radiation shield with well documented properties can help ensure meaningful comparisons between studies.
