WP
4
PotentiaMeter
Taking a Reading
38
higher (Ts-Tb is a positive number) than the
WP4’s chamber, take it out immediately, put the
cap on it, and let it cool for a few minutes
before sampling. Warm samples can cause con-
densation in the chamber and adversely affect
subsequent readings.
• The physical temperature of the instrument
should be between 5°C—43°C. Between these
temperatures, WP4 will measure samples of sim-
ilar temperature quickly and accurately.
• If you are sampling and a triangular warning
symbol appears in the top right corner, this indi-
cates that the mirror has become too dirty to
give accurate measurements, and you need to
clean the mirror and chamber before continuing
to sample. For more details about this symbol,
please refer to Chapter 12. For cleaning instruc-
tions, refer to Chapter 10.
• If a sample has a water potential drier than
about -60 MPa, WP4 will display a message,
accompanied by the flashing light and beeper,
notifying you that your sample is too dry to be
C
-1.84 MPa
24.7
pF 7.38
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