AquaLab 3TE



+ reproducible results
+ stable calibration
+ quick measurements
+ nice design
Navigation: Water activity
  What is water activity
  Test Introduction
Test details
  Salt solutions used
  Calibration samples used
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  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 ADAB  
  Price € ~ 8 000  
  Accuracy ±0.003 aw  
  Interval 0 - 1.000 aw  
  Instructions Yes/No  
  Samples ~ € 110 for 50  
  Own media Yes/??  
  Manual in


AquaLab 3 delivered very accurate
results. The instrument was not,
however, possible to adjust to give
even better results.

Optimisation of results were possible
using continuous measurements
in AquaLab and storing results in a
connected PC.

Each time a measurement was finished,
AquaLab wrote aw and temperature to
its RS232 port. The aw values were
given four digits, one more than shown
by the instrument's display.

The data from the instrument could be
read directly by any RS232 software.

The Decagon software "AquaLink v. 3.0"
was quite simple, yet effective.
It displayed a list of results containing
computer time, time passed during
present run, aw and temperature.
A simple graph of aw versus recording
number was also shown.
The result files could be saved
and were possible to read with
a common text editor.

Due to the possibility to let AquaLab per-
form measurements in a continuous
mode, the instrument together with
software performed very satisfying.

A sample was inserted, a new file was
initiated at the computer and results were
streamed until the graph indicated that the
result were stable. Stability in the fourth
digit took 4-6 measurements.


- fan sound
- nonofficial calibration samples
- nondocumented calibration

Sensor technology

The instrument monitors con-
densation of water on a chilled
mirror. The temperature diffe-
rence, between sample and
mirror when condensation
occurs, is calculated into
water activity.
The sensor technology appears
to be superior to other types of
sensors, provided the sample
do not contain volatile solvents
like propylene glycol, that will
interfere with water during



Analyzing a sample was easy.

A sample was inserted into the measurement chamber by
turning a knob and pulling a drawer, inserting the sample
cup into a holder and closing the drawer.
The measurement was started by turning the knob again.



The design was simple and very appealing.
"Less is more" is apparently the designer's motto.

A surprising minor flaw in the design was that the RS232
cable could not be securely tightened to the instrument.

Another flaw in the design was the sound from the cooling fan.
It should be more silent in a quality instrument like this.

Temperature instability
The analysis temperature could be set in AquaLab 3TE
as opposed to the model AquaLab 3.
The temperature appeared not to be stable, however,
and drifted towards room temperature during analysis.



The manual was informative and easy to read.
It was translated into Swedish by the Swedish agent.



Tests on Decagon calibration samples gave excellent
results, and calibration was apparently not needed for
the instrument.

According to the manual, adjustment of linear offset,
but not of slope, is possible and is easily performed.
Offset adjustment is needed when the sensor mirror
becomes contaminated.
Slope adjustments are done by Decagon
representatives, but are said to be rarely needed .

Calibration samples
For adjustment of linear offset and for validation,
Decagon manufactures ampoules containing calibration
liquid, guaranteed by Decagon to show correct values.
Other calibration samples may be used.

Unfortunately, publications that document the absolute
reliability of the ampoules have not been found.



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

Instruction video
A CD containing manuals and a very instructive video,
showing how to clean the measurement cell, should
it be contaminated, was included with the instrument.


Measurement results

The results are discussed in Summary - Desktop instruments

The instrument was used as delivered, i.e. was not calibrated.

The results from the Decagon calibration samples,
DecCal1, were excellent.

SatSalt2 and SatSalt3
The salt slurries SatSalt2 and SatSalt3, analysed 11 days later,
gave almost identical results.

The results were deviating slightly from literature values.

When the salt slurries were analysed at 25 °C (not shown),
the results were about identical as obtained at 22.5°C .

  Measurements and ending
criteria DecCal1,  Decagon
calibration samples:
Fourth reading was final result
SatSalt2: Salt slurries:
Fourth reading was final result
SatSalt3:  Salt slurries 11 days later:
No deviation in fourth figure

Compare with results from
HygroLab or LabMASTER

      Deviation versus aw for AquaLab 3TE.    
  Test of HygroLab 2   aw instrument test introduction      
  Test of LabMASTER   Summary - Desktop instruments EminTech Start Page