When the level builds up inside the tank the float moves up
and the counter weight moves down across a scale indicating
the level inside the tank.
Operation of the switch: The counter weight or the indicator
which carries a magnet operates the magnetic switch which
is kept inside the flameproof or weatherproof enclosure.
Operation of the transmitter: The rotating pulley rotates a
precision wire wound potentiometer and the resistance value
varies due to this movement. The change in resistance value which
is directly related to the measurement of level in mm, transmitted
to the control room or local control panel as 4-20 mA output.