5
•Clean your probe regularly during use. For cleaning instructions see this manual under
‘Clean’.
• Ensure samples or buers are well mixed to obtain correct measurement values. This
may be done by a magnetic stirrer or by stirring with the probe for at least 5 seconds.
Stop stirring and record results when the read-out is stable.
• Make sure the medium is in contact with both the ISFET sensor and the diaphragm
simultaneously.
• Make sure that the medium which is being measured, is providing a “hydrogen ion
bridge” between the ISFET and the diaphragm. Without a proper uid (or semi-solid)
connection between these both, no (stable) measurement can be performed. A good
rule of thumb is to have at least the rst 10 mm from the probe tip to be immersed
during measurements and calibrations. See also this manual under ‘Probe specic
information’.
• Buer-handling: pH 7.00 buers (phosphate-based) and pH 4.00 buers (biphtalate-
based) are less susceptible to carbon dioxide contamination than pH 10.00 buers
(borax or carbonate based). When slope errors occur, it usually indicates a failing probe
or a contaminated buer. If slope errors occur when using a pH 10.00 buer, try
calibrating with pH 7.00 and pH 4.00 buer. If a good slope is achieved, try a new bottle
of pH 10.00 buer. Buers in a convenient twin neck bottle are available from Sentron or
our dealers.
• Tris buers and samples containing proteins form impermeable layers on surfaces, and
require special attention when being used. These types of samples should be measured
quickly and the probe should be rinsed thoroughly with demineralized water between
samples. Avoid prolonged immersion in samples containing Tris or proteins. When
testing is complete, rst clean the probe with tap water and a laboratory detergent and
subsequently rinse with demineralized water.
• When testing in direct sunlight or on a bright reecting surface, please use brown,
opaque or shielded sample containers. Very bright light might inuence the
performance of the sensor.
Operating tips
