An insulated electrode is placed in the
boiler and the length should be sufficient to reach the water at all acceptable
levels. The insulated electrode and the boiler work as a capacitor with the
water and the steam as a variable dielectric medium. The capacitance of the
”capacitor” is converted into a current signal. 0% of water in the
level glass corresponds to 4 mA and 100% corresponds to 20 mA. The measuring
result is rather sensitive to foam in the boiler and deposits on the electrode
influences negatively on the measuring results.
This method is relatively new as level control in steam boilers although it has
been used for a long time for dry substances such as grains in warehouses.
An insulated electrode is placed in the
boiler and the length should be sufficient to reach the water at all acceptable
levels. The insulated electrode and the boiler work as a capacitor with the
water and the steam as a variable dielectric medium. The capacitance of the
”capacitor” is converted into a current signal. 0% of water in the
level glass corresponds to 4 mA and 100% corresponds to 20 mA. The measuring
result is rather sensitive to foam in the boiler and deposits on the electrode
influences negatively on the measuring results.