Siemens Rapidlab 1200, Руководство оператора, Страница: 52 / 448

1-32 Rapidlab 1200 Operator’s Guide: System Overview and Intended Use
02087462 Rev. V
The reference sensor contains a silver (Ag) wire, coated with a layer of silver chloride
(AgCl) and an ion permeable polymer, surrounded by a saturated potassium chloride
(KCl) solution. By ensuring that the concentration of Cl
-
remains unchanged in the
solution, the reference sensor maintains a constant electrical potential. A potassium
chloride (KCl) block is in the reference sensor solution chamber to ensure a saturation
solution of KCl at 37
°
C.
Figure 1-29 Reference Electrode
A permeable cellulose membrane separates the KCl solution from the sample and provides
the ionic conduction between the KCl solution and the sample. The membrane completes
the conductive path to the sample from the fixed half-cell potential that is required for the
measurement.
The Ag wire conducts the half-cell potential of the reference sensor to the measurement
device where it is compared to the potential of the measuring sensor. The potential
difference measured reflects the concentration of analyte in the sample. Although the
reference sensor provides a constant potential from sample to sample, the potential
difference measured between sensors varies with each sample.
1 Solution chamber
2 Saturated potassium chloride solution
3 Silver/silver chloride electrode
4 Sample path