Vibrating Level Switches - Hycontrol Diamond Point DP140

Switches for Solids Applications

The design of a vibrating level switch for solids must be fundamentally different to the design described for liquids. If two large parallel blades were used on powders or solids it would be too easy for product to build-up and become lodged between the blades causing the oscillations of the switch to stop regardless of product level.

For solids applications on products ranging from cornflakes to coal, it is preferable to have only one blade in contact with the product. This eliminates the potential for bridging between the forks and ensures that the switch does not give false alarms.

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 so minimising the effect of build-up on tank walls.

Advantages of Vibrating Probes

• No mechanical moving parts to wear
• No maintenance required
• Simple to install - no adjustments required
• Unaffected by environmental changes
• Unaffected by dust clouds and agitation
• Maximum versatility