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Vibrating Tuning Fork Liquid Level Switch

The Magne-Sonic Series 100 is a two wire device which may be installed in any position in a pipe or vessel to detect the presence of a liquid.

The Series 100 has a tuning fork style probe which vibrates at its natural frequency when in air. A piezoelectric crystal system is used to create a 1200 Hz vibration in the tuning fork. As the tuning fork is covered by a liquid or slurry, a corresponding shift occurs in the vibrating frequency of the tuning fork. This shift is being monitored continuously and once a present threshold is exceeded, the output changes status.

A standard two core cable is used to connect the switch in series with the load. The solid state output stage acts as a simple SPST switch, operated by liquid presence.

When specifying the standard 2-wire output version, the switch may also be interfaced directly to a 3 wire 24VDC PLC using a third PLC terminal on the circuit board. When relay output is required a SPDT dry contact output version is available with selectable high or low level fail-safe.

The new option "W" provides a unique step change output for 2-wire 24VDC applications. This option is similar to the DIN 19234 (NAMUR) Switching Levels except it is not suitable for I.S. applications - drawing 16.8 MA when "on" and 6.0 MA when "off'. See Larger Image

The Series 100 includes a status indicating LED which may be viewed through a lens in the NEMA 4X enclo­sure cover or with the cover removed, on the explosion proof model. The LED will flash approximately once per second when the switch is "off' and will remain constantly lit when the switch is "on".

The LED gives an indication that the switch is functioning correctly and gives a visual indication of the state of the relay.

A fail-safe switch on the circuit board is provided for the user to select either "make" when dry - the normal condition - or "make" when wet, as would be selected for low level duties.

The fact that this device is vibrating normally when dry makes it ideal for use in high level detection applications.

Any change in the sensor signal, however caused, will result in a status change of the switch and an alarm may be activated. When included in a fail-safe circuit this device provides an extra degree of fail safety improving system integrity.