The vibrating fork type level switch working principle is simple and effective. This makes vibrating fork type level switches (a.k.a. tuning fork type level switches) reliable, cost effective and very popular for use in detecting the presence or absence of liquids and bulk solid materials. The vibrating fork type level switch working principle is based upon detecting the change in harmonic vibration frequency of the sensing element as a result of the presence of the target media.
The vibrating fork type level switch working principle uses a tuning fork shaped sensing element with two tines inserted into the bin or tank where the target media will be present. The tuning fork sensing element is placed into vibration at its natural resonant frequency by establishing motion in the sensing element or fork. In most the most common embodiment of the vibrating fork type level switch working principle the harmonic vibration of tuning fork sensing element is established using Piezoelectricity.
Typically there are two Piezoelectric elements or crystals, often made of quartz. When these crystals are compressed or pulled under tension they generate an electric signal. Conversely when electricity is applied to these crystals they produce motion. This motion is attached to the fork sensing element and vibration at the natural resonant frequency of the mechanical fork is created. A second piezoelectric crystal is used to transform the motion received from the first crystal back into an electric signal. When the fork sensing element vibrates free in air the measuring system sees this as one state (material not present). When the target material or fluid becomes present, the frequency of the vibration is changed and the second crystals electric signal changes, thereby detecting the material or fluid presence. Some background on the use and application of quartz crystals can be viewed in this video Production and Use of Quartz Crystals
The vibrating fork type level switch working principle is indeed simple, effective, reliable and cost-effective means to measure or detect the presence and absence of liquids and bulk solids.