HygroLab 2
with AwVC-DIO



+ lower price
+ may use 4 sensor cells
+ may take larger samples
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HygroLab 2
  Swe.agent SWEMA  
  Price € 2 000 - 3 000  
  Sensor AwVC-DIO  
  Accuracy ±0.005 aw
+1.5% of read
  Interval 0 - 1.000 aw  
  Instructions Yes  
  Samples ~ € 40 / 5  
  Own media Yes  
  Manual /
in Swedish
- slow
- less reproducible
- calibration needed
- defective demo instrument


According to the Swedish agent,
and to the transport documents,
HygroLab 3 should have been
delivered to EminTech for testing.

Once tests were started, however,
it was realized that the model
delivered was a HygroLab 2.

The main difference between
HygroLab 2 and 3 appears to
be the possibility to run AwQuick
(see below) in HygroLab 3


Sensor technology

HygroLab 2 was used using the probe AwVC-DIO. The probe
measures electric properties of a polymer, sensitive to water


As seen in the part "Design", the PC soft-
ware was a substantial part of HygroLab 2.

HygroLab 2 sends aw and temperature
data to the RS232 port after request from
a PC. The communication protocol was
covered in the manual

The Rotronic software "HW3 v. 2.1.2_b"
was responsible for communication with
HygroLab 2 from the PC side.
During installation, the software required
a serial number and asked to register
users to Rotronic. It also appeared to
list network connections, which is a
possible security threat.

After installation the software run
smoothly. Programming could be better,
4 program windows and not showing
program status implied that learning
period became longer than it had to be.

The current aw and temperature was
displayed on the screen.
It was possible to log the data to a text
file for later viewing.

A stability criterion, defining when the
computer should indicate end of
measurement, was possible to set.

Viewing of graphs using the software
HW3 appeared complicated and was
not attempted. Instead the result text
file was pasted into a Microsoft Excel
spreadsheet which displayed the graph.

Calculation of final result
from the aw versus time curve

By buying an addition to the software for
about € 1 000, a function called AwQuick
became available. This feature gave the
possibility of calculating final aw from the
aw versus time curve, obtained before
stable results would normally be obtained.

A test run at 10 minutes analysis time
gave unreliable results (not shown).

Series SatSalt3 of salt slurries were
tested using AwQuick with analysis
time set to 30 min., except for samples
at aw = 0.98 and 1.00 that were given
2x30 minutes.


Handling was simple, provided a PC was used to control
the instrument. Alternatives to PC control were not tried.

A sample cup was inserted into the lower part of the probe
and the upper part was placed on top.
No clamping device was needed to seal the probe.

The measurement was started by pushing a button
in the PC program

A pair of tweezers was needed to get the sample cup
out of the probe without spilling.


This instrument was no beauty but responded rapidly.
The sensor cell AwVC-DIO was nicely manufactured and

The main instrument, i.e. HygroLab 2, was mainly
functional as a bridge of information to the computer.

Pushing buttons were uncomfortable.

The display was initially hard to read.
The second day of testing the display went blank for good.
The instrument was then started by pushing the on/off button,
and using the blinking light on the sensor to confirm that the
instrument was running. It was then controlled from the PC.


The manual (in English of German)was extensive. By using
the list of contents, it was possible to find relevant information.


In spite of enclosed calibration certificates, the instrument
had to be calibrated before real measurements could start.

Using the HW3 software, the instrument was calibrated
with help from the manual. Calibration was simple.
Two calibration points were needed, one for offset
and one for slope.
Any calibration sample could be used for calibration.
The calibration took about two hours.


Sample cups - also larger samples are possible
Sample cups volume: 15 or 50 ml.
Sample heights: 13 or 38 mm.

More than one measurement simultaneously
The same instrument can be used to run 4 measure-
ment cells.

Measurement results

The instrument was calibrated using Novasina calibration
samples 33 and 75 at about 22.5 °C

The results from HygroLab were less exact than from
AquaLab and LabMASTER. Note that the scale in the figure
below is different from the figures of AquaLab and LabMASTER..

As the measurement cell of HygroLab, AwVC-DIO, is the same
type as was used when testing Rotronic HygroPalm AW1, it
was not surprising that the results resembled each other.

The results from the Decagon calibration samples, DecCal1,
gave results within specification (±0.015 aw).

The Novasina calibration samples, series NovCal1,
gave results within specification.

The results from the salt slurries, SatSalt2, were deviating
from specification at aw = 0,98.


Results from salt slurries, SatSalt2 run 11 days after SatSalt2,
were similar to SatSalt2.


Measurements and ending criteria

DecCal1,  Decagon calibration
Horisontal line in graph
NovCal1: Salt slurries:
Horisontal line in graph
SatSalt2:  Salt slurries:
Horisontal line in graph
SatSalt3:  Slurries 11 days later:
AwQuick 30 min

Compare with results from:
AquaLab or LabMASTER

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