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are selected for metering or recording. If the logger is not recording or
waiting for a delayed start, the power supply is switched off at midnight.
This power supply is the reason for the decreased battery life. This is
reflected in the displayed battery life in the STAT function.
9.7 Care and Use of pH Probes
pH probes are very sensitive. Depending on their age and history, they
can take a while before settling on a value. During probe calibration, each
pH probe should be allowed enough time to settle. Always wait until the
reading to stays constant for ten seconds. This is usually fairly quick, but
old probes, probes that have been allowed to dry out, and probes that
have been in either a very high or very low pH may take a while to settle.
Occasionally, the output of a probe may continue to wander, never really
settling on a value. This is an indication that the probe has expired and
should be replaced.
As explained in the above section, the logger will power down its pH input
circuitry under certain conditions. When this happens, any pH probes that
may be connected will deteriorate more quickly than normal, so it is
strongly recommended that any pH probes be disconnected and stored
properly when not in use.
The tip of a pH probe should always be kept wet, so there are some
important points to remember when storing one. After use, the tip of the
sensor should be rinsed in pH 7.0 buffer solution. The end cap should
then be sealed on while the tip is still wet.
These actions should help to preserve the life of the probe, and make for
speedier calibration when it is next used.
