The water level is measured between the electrode tips and the vessel wall/protection tube or reference electrode, and analysed to see if limitation is necessary. The medium has to be electrically conductive for this method to be successful. "High Integrity" alarms continuously monitor the insulation resistance and the electrode cable feedthrough. In addition to self-monitoring, the electronic control unit performs a self-test that also includes the output contacts. "High Integrity" units are required for boilers with a working pressure of > 0.5 bar. In conductive systems, the switchpoints are determined by the shortening of the electrode tips.
"High Integrity" alarms have SIL certification.
SPECTORmodul SIL 3,
SPECTORbus SIL 2
SPECTORbus comprising: NRG 1.-40 / NRS 1-40 (LW); NNRG 1.-41 / NRS 1-41 (HW)
SPECTORmodul comprising: NRG 1.-50 / NRS 1-50 (LW); NRG 1.-51 / NRS 1-51 (HW)
The electrode tip and vessel wall/protection tube (reference) form a condenser. The dielectric medium is the air or the filler. As the level changes, the capacitance between the electrode and the reference also changes due to the varying ratios of the dielectric constants air and filler. This in turn provokes a change in the sensor's output signal that is proportional to the water level. The switchpoints can be adjusted on the electronic control unit, and can be multiplied by connecting several electronic control units in parallel.
SPECTORbus comprising: NRG 26-40 / NRS 2-40 bzw. NRR 2-40
SPECTORmodul comprising: NRG 26-21 bzw. NRGT 26-1 / NRS 2-5. bzw. NRR 2-5