Pawkit
Operation
19
button (I) will wake up the instrument and display
the last water activity measurement.
Calibration
As mentioned earlier, the Pawkit takes water activity
measurements by measuring the change in electrical
properties of a special polymer held between two
electrodes. Due to the nature of the dielectric
humidity sensor, there may be times when you may
need to calibrate. This section explains how to do
so. Calibrations should be verified frequently with
salt standards and adjusted as needed.
Calibration Standards
The Pawkit uses 2 calibration standards: 6.0 molal
NaCl (0.760a
w
), and 13.41 molal LiCl (0.250a
w
). You
received a small supply of these standards with your
instrument. These standards are specially prepared
salt solutions at specific concentrations for constant
and accurate water activity measurements. They
have been produced under a strict quality assurance
regime, and their accuracy is verified by an inde-
pendent third party. They are very accurate, easy to
use, and readily available from Decagon Devices.
Most importantly, they greatly reduce preparation
errors. Because of these reasons, we recommend
using these standards for the most accurate calibra-
tion of your Pawkit. The calibration standards are
shelf-stable for one year.
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