• Endress+Hauser (India)

Liquid level switch

Endress+Hauser, Mumbai-based company, offers Liquiphant T FTL 260, a level switch for liquids, of which more than 1 million units have been sold worldwide. One of the prime reasons for this success is that the level limit switch Liquiphant T is universally applicable. It is also used in all those applications where float switches are not suited because of build-up, turbulences, currents, air bubbles, etc. The fork of the Liquiphant is driven by a piezoelectric crystal to vibrate with its resonance frequency of 400Hz in air. When immersed in a liquid, the filling material changes the oscillation frequency. The fork oscillates then at a frequency between 120 Hz to 350 Hz in liquids. This change in frequency is the basis for the measurement in levels. Outside this frequency range the instrument will recognise a malfunction and will indicate the alarm. The change in oscillation frequency occurs during immersion due to the change of the density from air into liquid as well as the length of the fork. A non?stop operation of the Liquiphant is guaranteed if the minimum density of the liquid is more than 0.7 g/cm3 and with a viscosity of up to 10000 mm2/s. The switching signal is either a PNP transistor or a two wire AC (19 ? 253 V) output. Tuning forks, used in level measurement, are mounted close to the height of the limit and or lower levels, usually at the side of the silo. The mounting position should be considered so that the filling does not affect the function of the sensor. If some basic rules are considered, these tuning forks are universal and reliable limit switches. Solid state electronics require no maintenance, no setup, no calibration or trained personnel.