Solid Level Switches

Working Principle : 

1. Electronics of LSV excites the piezo-electric-crystals inside the tuning fork, which makes the fork tines vibrate at their natural resonance frequency in free air.
2. Amplitudes of vibration are above threshold when tines are free to vibrate.
3. When material touches the fork tines, vibration stops as resonance gets disturbed.
4. Amplitudes of vibration, as sensed by electronics falls below the threshold strength, material presence is thus detected.

Working Principle : 

1. Vibrating rod is a single element tunned mechanical element-type level sensing device.
2. Electronics of LSV-R excites the piezo-electric-crystals inside the tuning rod, which makes the rod vibrate at it’s natural resonance frequency in free air.
3. When Material touches the rod, vibration stops as resonance gets disturbed.
4. Amplitudes of vibration are above threshold when rod is free to vibrate.
5. Amplitudes of vibration, as sensed by the electronics falls below the threshold, Materials presence is thus detected by observing the amplitude of vibration.

Working Principle

RF Admittance is a static level sensor with no moving parts. Its sensing parts are:-
1) Earth Extension (body)
2) Compensation Shield
3) Sensing Rod

…which form three capacitances:-
1) Shield Earth Capacitance
2) Shield Sense Capacitance
3) Sense Earth Capacitance

A Sine wave of high frequency is fed into both Sensing Rod as well as Compensation Shield. Voltage at shield is equal to voltage at sense, no effective current flows between sense and shield.

This same voltage or equi-potential drive to sense and shield removes shield-sense capacitance from the
measurement. Shield-earth capacitance is ignored by circuit.
This removes the effect of material coating on probe.

Which makes the probe selectively sensitive and by virtue of electrostatic loading of shield, it actually makes admittance device reverse sensitive in the shield-earth region.

Since, level is detected by measuring sense-earth capacitance only, level is not sensed until sufficient amount of material covers sense & earth combined.

Working Principle

LMC Capacitance type limit switch is a static level sensor, Sensing parts of LMC capacitance level
limit switch are:
1) Earth Extension (metallic process connection may be used as earth in-place of earth extension tubes).
2) Sensing Rod (or Rope as per application).

The capacitance is formed by the sense rod and earth
When no material is present, the capacitance is analogically a multiple of probe dimension and dielectric constant of air {ε(air)≈1}.

When the material is present, the capacitance gets multiplied by dielectric constant of the material 
This variation in capacitance, which is due to the dielectric property of material, is then translated into switching output by the LMC Capacitance level limit switch.
With two point independent type switches, two different values are mapped to two different outputs and thus only one level switch can provide two different level outputs.

Working Principle :

• Rotating paddle type level switches are basically a spring loaded, eccentricaly driven rotating vanes or blades which rotate at a very slow rotation of one revolution per minute, using an ac synchronous motor.
• When no material is present, rotating vanes, (or blades or paddles) are free to move and motor is held by a spring in its normal position.
• When material reaches the rotating vanes, it tries to stop the rotating of vanes, causing a reverse rotation of motor and stress on the spring which is holding the motor.
• When motor rotates to a degree where limit switch is present, the power to motor is turned-off and output is generated.
• As soon as material level falls, the vanes become free to rotate once again, causing the motor to turn back to its normal position due to stress on the spring holding the eccentric-drive, synchronous motor

Working Principle : 

LMC30 is a compact capacitance level limit switch for solids specially intended for see though plastic window material sensing in packing hoppers. LMC30 can be mounted on any M30 compatible mounting hole and it is supported by two supplied mounting nuts. LMC30 deploys touch sense on its rear, so as to set its switching point and no potentiometer or touch button is present enhancing operational life of the device