Test summary

water activity



Importance of validation
  The tests of the three water activity measurement instruments
clearly demonstrated the importance of result validation.
Without calibration all three instruments would have given
erroneous measurement results already after three weeks.

Two of the three tested sensors gave significantly different measurement results after some time of testing.

At least initially, before the properties of an instrument is
known, it is recommended to validate the readings before
and after each measurement, or at least once a day.

Decagon recommends validation once a week and sell
highly advised calibration ampoules in packages of 50
for one year supply.
HygroPalm AW1 with sample cell AwVC-DIO
    performed very well during the measurements.
The results showed only small variations.

In case analysis time should be important, the extra-
polation function appeared to work well, although
several consecutive measurements increased the
reliability of the results.

The only major flaw, the battery problem, may be solved
using battery switching routines, an optional docking
station or upgrading to Rotronic HygroLab.

Also the price of this instrument was attractive.
Decagon Pawkit
    This pleasant little instrument showed an initial instability
but appeared to give stable results after calibration.

If portability is important this instrument well worth

The good manual and the dedicated Swedish agent pro-
vide additional arguments for this device (in Sweden).
Testo 650 with sample cell 0628.0024
    was the most expensive instrument in the survey. As cali-
bration instructions are charged extra, the price became
even higher.

In spite of the impressing documentation provided, the instru-
ment did not deliver measurement results as expected.

In case additional features should be used, like connecting
other sensors to the instrument, this instrument may be
worth consideration.
Navigation: Water activity
  What is water activity
  Test Introduction
Test details
  Salt solutions used
  Calibration samples used
  Desktop instruments
  Portable instruments
  Desktop instruments
  Decagon AquaLab 3TE
  Novasina LabMASTER-aw
  Rotronic HygroLab 2
  Portable instruments
  Decagon PawKit
  Rotronic HygroPalm
  Testo 650
  Desktop instruments
    Portable instruments
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