The operating principle is the same for all vibrating probe level switches.  A piezo-electric crystal is used to force a blade to oscillate at its fundamental frequency (natural resonance).  When the blades come into contact with the process medium the natural frequency of oscillation is damped; the electronics sense the change in frequency which causes the unit to switch. 

The different electronic outputs to choose from allows the user to switch a load on/off or to interface directly with a computer.  The units can be programmed to sense high or low level and failsafe high or low, with adjustable sensitivity to eliminate false switching.  The switch is only sensitive at the tip, which minimises the effect of build-up on tank walls, on its operation. 

As the damping effect (resistance to vibration) of low viscosity liquids is very small, it is common to use two relatively wide blades to sense the presence of liquid levels.  These blades can be short in length for minimal intrusion into the vessel or for use in pipes.

The TF Series

This rugged design of switch is used throughout the process industries.  It is available with a wide range of flanged or screwed process connections and can have extensions, enabling the probe to reach 3 metres into a tank if required. 

The wetted parts of standard switches are 316 stainless steel but special Halar coated and Hastelloy switches are used for extremely corrosive applications  and hygienic probes are available for the food industry. 

The switch has visual indication of its on/off status and a magnetic test point on the side of the housing to allow an operator to check the function of the switch.

An intrinsically safe and explosion proof version of the switch is available for hazardous areas. 

The MTF Series

The MTF is designed specifically for OEM equipment and has a smaller and more cost effective configuration, but still retains the status LED and test point featured in the TF series.

 This compact low cost  switch has a rugged stainless steel body and stainless steel forks for use in a wide range of  liquids