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
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.