WP
4
PotentiaMeter
Theory
47
MPa, temperature difference measurements need to
be accurate to 0.005°C.
WP4’s infrared thermometer measures the differ-
ence in temperature between the sample and the
block. It is carefully calibrated to minimize tempera-
ture errors, but achieving 0.005°C accuracy is diffi-
cult when temperature differences are large. Best
accuracy is therefore obtained when the sample is
near chamber temperature.
Another effect of temperature on water potential
occurs with samples that are near saturation (like
many soil samples). A sample that is close to 0.00
MPa and is only slightly warmer than the sensor
block will condense water within the block. This
will cause errors in the measurement, and in subse-
quent measurements until the condensation disap-
pears. The Ts-Tb function helps the user ensure that
the sample won’t condense on the sensor block.
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