I purchased Tempest during the Indie–gogo and mounted it on 13 foot pole in the backyard. 5 feet of that pole was the gray type PVC. The rest was a 4 x 4 mounted in the ground using concrete.
I have always had lower wind velocity’s that I was observing elsewhere.
Because of battery problems, I received a replacement device and this time I mounted it on top of a links of electrical conduit. It had the extra effect of adding for more feet to the pole.
Now it’s reading more accurately. What I suspect is happening with the PVC is that it’s too flexible and lets the wind push the Tempest away, causing the wind velocity to be measured incorrectly.
Now it mirrors my handheld anemometer.