Single Item Test     If Red Cursor placement is OK, Turn the Filter ON by clicking on the filter switch in the graph window. Important!   The following should be observed: Viewable graph range changes to + 1000 Hz of the Red Cursor The Frequency Filter is Turned ON A Search Range for the set filter is displayed. V9 searches for Main Frequency (F) in this range filtering out all lower and higher frequencies. The rest of calibration is executed as usual with the Filter enabled ensuring: Problematic secondary frequencies are eliminated. Correct, high accuracy readings within the set search range are picked up.