+ reproducible results†
+ impression of quality
+ good programming
+ calibration samples
† when calibrated
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
  Swe.agent ProReg Control AB  
  Price € ~ 8 000  
  Accuracy ±0.003 aw
  Interval 0.03 - 1.00 aw  
  Instructions Yes<  
  Samples Included-longlife  
  Own media No  
  Manual in


LabMASTER continuously writes actual
aw and temperature to the computer
interface through either of the ports
RS232 or USB.

The data from the instrument could
be read directly by any RS232 software.
The software "NOVALOG32 v.1.12"
was, to be nice, hard to understand.

Saving files, starting (or ending?)
logging was implemented in a manner
as it was meant to be annoying.

It should be possible to get a graph
from the data on the screen, but if this
graph should be drawn in real time or
after the measurement was uncertain.

Should the program become more
user friendly, it would be beneficial
for documentation and for graphing.

During the present tests, however, a
simple RS232 logging program was
used for documentation of data.

Software inside LabMASTER-aw
The software inside the instrument
was, in contrast to the PC program,
really useful.

The instrument was possible to
program in a number of ways,
and could store 10 sets of analysis
parameters. This would be beneficial
in laboratories that repeatedly analyse
samples that need to be run at,
say both 35 and 25 °C.

The internal software may also control
several simplified LabMASTERs called
LabPARTNER. An additional communi-
cation port was present for that purpose.

A stability criterion, defining when the
instrument indicate end of measurement,
was possible to set.
The function appeared reliable and the
instrument did not report "false" results.

The instrument could also produce a
primitive print of a measurement
result on a suitable printer.


- heavy design
- unclear manual
- illogical PC software
- calibration needed

Sensor technology

The instrument measures
variation of electric properties
of an electrolyte with humidity.


Analyzing a sample was fairly
easy. A sample was inserted
into the measurement chamber
by opening a lid and putting the
sample into a holder. The lid
was closed and the measure-
ment was started by pushing a
button. The lid required some
strength for handling.



The design could be better. The construction
of the instrument, however, gave a feeling of robust quality.

Good temperature management
Temperature stability appeared to be superior in this instrument.
The set temperature appeared to be stable and when sample
chamber temperature was changed, the temperature was rapidly
Temperature equilibration in the instrument deserves attention.
Beside the sample holder in the measurement chamber, an extra
space was added for storing the next sample to be analyzed. This
was claimed to shorten the analysis time.



The manual was complicated to read, partly because this instru-
ment was more computerized than the two other.

Instead of being a "read and do" manual, the type could be
defined as "read for hints and try on the instrument".
Due to the logic programming of the computer in the instrument,
it was, however, possible to use the instrument after having read
parts of the manual.

The manual was translated into Swedish by the Swedish agent.



In spite of enclosed calibration certificates, the instrument
had to be calibrated before real measurements could start.
After getting hints in the manual, calibration was possible
due to the good computer program in the instrument.
Six calibration samples were used for calibration.
Calibration took more than six hours.

Calibration samples
Only Novasina calibration samples were recommended for cali-
bration. They were included with the instrument and claimed
to be usable over many years.
In case the claims of calibration sample stability are correct,
these samples were a nice addition to the instrument.



Sample cups
Sample cup volume: 11 ml.
Sample height: 10 mm.
Sample cups for Decagon AquaLab and
Novasina LabMASTER were almost identical.

Endpoint criteria
During measurements the instrument followed
set criteria for when a result is stable very well.


Measurement results

The results are discussed in Summary - Desktop instruments

The instrument was calibrated using Novasina calibration
samples at 25 °C. Subsequent analyses at 22.5 °C gave
results shown in the figure below.

The Decagon calibration samples, DecCal1, showed
high deviation values at aw = 0.25 and 0.33.

Some results from the salt slurries, SatSalt2, were deviating
from specification.

Salt slurries at aw = 0.11, 0.33 and 0.75 were made from the
same chemicals as used in the Novasina calibration samples.
These samples showed good reproducibility and were
within specification.

The results at aw = 0.98 and above appeared to be less
accurate than measurements at lower aw values.

Analysis of pure water, aw = 1.000, failed, as indicated
by a high value in the diagram.

The Novasina calibration samples, series NovCal1, gave
results within specification (±0,003 aw), except for aw=0,98.

SatSalt3, run 11 days after SatSalt2, showed a deviation from
SatSalt2 with about 0,003.

  Measurements and ending criteria

DecCal1, Decagon calibration samples:
Second analyze was final result
except 0,25: after 5 hrs
SatSalt2: Salt slurries:
First analyze was final result
NovCal1: Novasina calibration samples:
First analyze was final result
SatSalt3: Salt slurries 11 days later:
Two identical results.


Compare with results from:
AquaLab or HygroLab

      Deviation versus aw for LabMASTER-aw.    
  Test of AquaLab   aw instrument test introduction      
  Test of HygroLab 2   Summary - Desktop instruments EminTech Start Page