A Tuning fork is kept in mechanical vibration at the resonance frequency by piezo ceramic elements. THe fork can be side or top mounted. When the service material covers the tines of the fork, vibrations are damped. This is sensed electronically and a processed signal is used to energize a relay whose contacts in turn are used for annunciation or control. Two basic type of constructional arrangements are available. In one, the electronics is separated from the fork, whereas in the other, it is integrated. Mounting arrangements of the screwed or flanged type confirming to various standards, high temperature versions up to 200⁰ C without the necessity of elaborate cooling arrangements and flame proof versions for hazardous areas are also available.

SLAM Series can be used for  

• Level limit detection of fine, coarse, solids of low dielectric constant that have a tendency to stick, coat and develop static charge at high vessel temperatures.
• For switching off conveyors when the vessel is full, to avoid overflow.
• For indicating on empty tank well in time to avoid production stoppage. Special probe design for detecting level of fly ash in ESP hoppers.

The measuring system for the SLAM series consists of an evaluation unit and an immuno-coat probe. The probe comprises sense and shield electrodes electrically isolated from the metallic tank by means of suitable insulators. The sense electrode and the vessel wall serve as the two electrodes of an imperfect capacitor with the service material as the dielectric. A change in material level causes a change in dielectric, which in turn causes a change in admittance of this tank capacitor.
The processed signal is used to energize or de-energize a relay whose output contacts are available for annunciation or control.
An accurate measurement of this change affords an indirect measure of the level of material in the tank. The evaluation unit measures the change of admittance accurately by using radio frequency (R.F.) technique coupled with coat immunizing circuitry. R.F. signal transmission between probe and evaluation unit via a co-axial cable with a drain wire having driven shield arrangement eliminates cable capacitance and drift due to change of cable capacitance with temperature.