The 8201 pH sensor works as a single-rod measuring cell. The measuringelectrode and reference electrode are combined in one element. Anenamelled steel pipe is used as the basic carrier. The measuring electrodeis created by additionally attaching an ion-sensitive enamel layer(yellow) with metallic voltage conductor (positioned in the non-conductiveblue enamel carrier layer). An ion exchange of H+ions takes place onthe surface (gel layer) of this enamel layer. The Ag/AgCI reference electrode is located in the interior of the enamel pipe filled with electrolyte. Aceramic machined diaphragm is pressed into the lower end of the pipe.Voltage transfer takes place when the electrolyte makes contact withthe measuring solution via the annular gap of the diaphragm. A Pt1000for temperature compensation is also integrated in the sensor. The electrolyteused is 3-molar KCI, stored in a separate electrolyte vessel andpermanently connected to the electrode via a hose.The pressure of the electrolyte vessel is maintained slightly above process pressure by means of an attached pressure controller. For non-pressurised processes the static overpressure of the pressurevessel mounted approx. 0.5 m above the electrode is generally sufficient.

Due to the very slight permanent electrolyte flow that flows through the extremely small annular gap, contamination of the reference electrode is practically eliminated. Accidental operation without electrolyte is prevented by optional inductive level monitoring of the pressure container. When a minimum level has been reached, the electrolyte supply bottle in the pressure container is simply changed. Bürkert Type 8285 provides the analysis of the measured value. The maximum length of cable between electrode and converter (transmitter) should not exceed 5 m. pH electrode 8201 is supplied without adaptation. The appropriate set is selected according to the fitting/armature chosen. Different hygenic variations of Model 8201 are available. Various standard armatures type 8200 can be used as well.