Method of functional monitoring of vibration level switches; involves oscillating oscillator at current tuning fork frequency and frequencies of redundant band filters

摘要

The method involves using a tuning fork (17) connected in parallel with a balancing unit (16) forming part of an oscillator circuit (14,15,20-23). During level measurement, the oscillator circuit oscillates at the current tuning fork frequency and at frequencies of redundant band filters (14,15). The frequencies of the band filters vary between two values that depend on characteristic resistances (20,22) that can be connected to the band filters.