Additional information on pH and ORP (MP-6 and MP-6p models)56.D.1.4 Sources of errorD.1.4.1 Reference junctionThe most common sensor problem is a clogged junction because a sensor isallowed to dry out. The symptom is a drift in the zero setting at pH 7. This explainswhy MP series meter does not allow more than one pH unit of offset duringcalibration.D.1.4.2 Sensitivity errorsSensitivity is the receptiveness of the glass surface. A film on the surface candiminish the sensitivity and cause a long response time.Figure 10 pH/ORP sensor construction1 Glass surface 5 KCl solution2 H+ ions 6 Glass3 Junction plug 7 Electrode wires4 Platinum button
