Dry Samples; Samples And Temperature - Decagon Devices WP4C Operator's Manual

Dewpoint potentiameter

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restrict water transfer. For short-term storage (< 3

hours) the cup lid is acceptable. If it will be a long time

before the measurement is made, seal the lid with tape

or Parafilm completely around the cup/lid junction.

Dry Samples

Samples that have a water potential drier than about -300

MPa cannot be accurately measured with the WP4C.

However, samples with such dry water potential values are

rare. When a sample's water potential value is drier than

about -300 MPa, WP4C will display an error message indi-

cating the lowest reading it could make on that particular

sample. For example, if you were measuring a dry sample

and the following screen appeared:

this screen indicates that the last water potential reading

the WP4C measured on this sample was -301.8 Megapas-

cals. Therefore, the actual water potential of the sample is

lower than the instrument can measure.

If samples are warmer than the chamber when they are

placed in it (Ts-Tb is a positive number), condensation

may occur and moisture may condense inside the block. In

order to prevent this, do the following:

< -820 MPa

PotentiaMeter

6. Sample Preparation

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