 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 boiler level measuringresult is rather sensitive to
foamin the boiler and deposits on the electrode influences
negatively on the boiler level measuring results.
This boiler level capacitance electrode measuring 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.
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