+ nice design, small size
+ good manual
+ good Swedish agent
Navigation: Water activity
  What is water activity
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Test details
  Salt solutions used
  Calibration samples used
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    Decagon PawKit
  Rotronic HygroPalm
  Testo 650
  Desktop instruments
  Portable instruments
- only two figures in result
- some instability
- slightly tricky unpacking
Links Decagon
Swe.agent ADAB
Price € ~ 1 800
Accuracy 0.02 aw
Range 0 - 1.00 aw
Instructions Yes
Samples ~ € 110 / 50
Own media Yes
Manual Yes
in Swedish Yes
Computer interface No
The design was appealing and
appeared to be done by an inno-
vative designer. I minor flaw in
design was, however, noted.
Before measurements could be
made, the instrument must be
unpacked, a stage that needed
reading of the manual. Once
unpacked, handling, like swit-
ching samples, was very easy.

Another nice property of Pawkit
was that it could show results
higher than aw = 1.00, i.e. the
result appeared not to be
manipulated by software.
The manual was very informative and was translated into Swedish by the interested
and service minded Swedish agent.

Calibration was easily performed by pushing buttons according to description in the manual.

The manual states that in case a measurement of a calibration sample gave a result within 0.02
of the nominal value, correction was not needed. Experience at EminTech gave, however, that when
careful measurements gave a deviation of 0.02, the instrument reading should be corrected.

Only two figures (e.g. 0.76) were shown in the result aw, implying that calibrations using e.g.
saturated Sodium Chloride (aw = 0.755 at 20 °C) was not applicable.

Measurement results
Only two figures were shown in the result aw, decreasing the apparent accuracy.

As seen in the diagram, the second measurement series, PawK2c showed results about 0.01 aw
too high. After calibration of Pawkit, the series PawK3c and PawK4c gave reasonable results.
The behaviour is discussed in Summary.

In order to obtain reliable results from Pawkit, the measurements should be performed in a
manner not described in the manual. The results shown from measurements PawK4c in the
diagram, was obtained using the routine that three consecutive measurements should give
the same reading. In the other series, less rigorous measurements gave results worse than
claimed by the specification.
      Deviation versus aw for Pawkit in four measurement series.    
  Test of HygroPalm   aw instrument test introduction      
  Test of Testo 650   Summary - Portable instruments EminTech Start Page