Test
Rotronic
HygroLab 2
with AwVC-DIO
EminTech
+ lower price
+ may use 4 sensor cells
+ may take larger samples
- slow
- less reproducible
- calibration needed
- defective demo instrument
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| Links | Rotronic Rotronic - USA HygroLab 3 |
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| Swe.agent | |||
| Price € |
2 000 - 3 000 |
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| Sensor | |||
| Specification | |||
| Accuracy |
±0.005 aw +1.5% of read |
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| Interval |
0 - 1.000 aw |
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| Calibration | |||
| Instructions |
Yes |
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| Samples |
~ € 40 / 5 |
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| Own media |
Yes |
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| Other | |||
| Manual / in Swedish |
Yes/No |
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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 actually HygroLab 2.
The main difference between HygroLab 2 and 3 appears to
be the possibility to run AwQuick (see below) in HygroLab 3.
HygroLab 2 was used using the probe AwVC-DIO. The probe measures electric properties of a polymer, sensitive to water absorption.
Handling
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.
Software
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.
Design
This instrument was no beauty but responded rapidly.
The sensor cell AwVC-DIO was
nicely manufactured and
designed.
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.
Calibration
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 measurement 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.
DecCal1
The results from the Decagon calibration samples,
DecCal1,
gave results within specification (±0.015 aw).
NovCal1
The Novasina calibration samples, series NovCal1,
gave results within specification.
SatSalt2
The results from the salt slurries, SatSalt2, were deviating
from specification at aw = 0,98.
SatSalt3
Results from salt slurries, SatSalt2 run 11 days after SatSalt2,
were similar to SatSalt2.
DecCal1: Decagon calibration samples:
Horisontal line in graph
NovCal1: Salt slurries:
Horisontal line in graph
SatSalt2: Salt slurries:
Horisontal line in graph
SatSalt3: Salt slurries 11 days later:
AwQuick 30 min
Compare with results from
AquaLab LabMASTER
