ASI Calibration

Purchased a 20-200 knot airspeed indicator as a backup to a Dynon.
It read zero when it first came out of the box. Still uninstalled but now reads 200 kts.
Is there a way of adjusting it back to zero?

Thanks, Tom

Have you removed the pilot and static line plugs. If not a pressure change may have caused your reading error..

Yes, plugs were removed.

Did someone blow in it to check it for movement? If so, it probably got damaged and would need to get fixed by an instrument shop.

No, never blow in.

This is a bit off the subject, but a friend much better at trigonometry than I am said to calibrate True Airspeed: Fly at a fixed indicated airspeed ( say 150 mph indicated) at 360 for a minute, record the ground speed and true airspeed; then do the same thing for heading 120, then again for heading 240 . Add both, divide by 3, and see if they match. If your Ture is a bit low, consider ( after determining no static leaks) putting a dam in front of both static posts to bring IAS up into actual.

Regards,

Gary