ROTRONIC HP23-AW User Manual

Page 2

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ROTRONIC AG, CH-8303 Bassersdorf
Tel. +41 44 838 11 44, www.rotronic-humidity.com
ROTRONIC Messgeräte GmbH, D-76275 Ettlingen
Tel. +49 7243 383 250, Fax +49 7243 383 260, www.rotronic.de
ROTRONIC SARL, 56, F - 77183 Croissy Beaubourg
Tél. +33 1 60 95 07 10, www.rotronic.fr
ROTRONIC Instruments (UK) Ltd, Crompton Fields,
Phone +44 1293 571000, www.rotronic.co.uk
ROTRONIC Instrument Corp, NY 11788, USA
Phone +1 631 427-3898, www.rotronic-usa.com
ROTRONIC South East Asia Pte Ltd, Singapore 339156
Phone +65 6294 6065, www.rotronic.com.sg
ROTRONIC Shanghai Rep. Offi ce, Shanghai 200233, China
Phone +86 40 08162018, www.rotronic.cn

SHORT INSTRUCTION MANUAL
Portable humidity and temperature instrument
for Water activity

General description
This short instruction manual covers special the Water activity function, for basic operation
consider the standard HP23 short instruction manual.

The detailed instruction manual can be found on the internet at:

www.rotronic-humidity.com

Aw Mode
This specialized mode is available only with model HP23-AW and is meant to be used exclusively
with the HC2-AW digital probes and is used for measuring the water activity (Aw) of product samples
and materials in bulk such as powders, seeds, etc. When set to operate in the water activity mode,
the HP23-AW automatically displays humidity as Aw (1.000 aw = 100 %rh). When measuring water
activity, the HP23-AW offers the following options:
•

Accelerated water activity measurement (AwQuick)

The HP23-AW uses an algorithm to accelerate the water activity measurement and provides a

result in typically 5 minutes. The measurement ends automatically and the display is frozen.
When temperature conditions are stable (both at the product and probe), the value measured
with the AwQuick mode is generally within ± 0.005 aw of the value that would be obtained by
waiting for full equilibration of the product and probe.

• Conventional water activity measurement (AwE)
The HP23-AW waits for the full equilibration of the measured product and probe. For most

products, this takes from 30 to 60 minutes. The HP23-AW automatically detects equilibrium
conditions (humidity and temperature) and ends the measurement at that time by freezing the
display.

Data logging and probe adjustment are available in the water activity mode, but when using
these functions humidity is shown as %rh as opposed to aw. The other standard mode functions
are not available.

Enabling the Aw Mode and selecting the measurement option
To set the HP23-AW to the water activity mode:
• Press the MENU key and select “Aw Mode”. Press ENTER to activate the Aw Mode menu.
• With the “Enable” menu item highlighted, press ENTER and use the UP or DOWN arrow key to

select ON. Press ENTER to conﬁ rm the selection.

• Use the DOWN arrow key to select the “Mode” menu item and press ENTER. Use the UP or

DOWN arrow key to select either AwQuick or AwE. Press ENTER to conﬁ rm the selection. Any of
the settings (see below) for either the AwQuick or AwE option can be changed after using the
UP or DOWN arrow key to highlight the setting and by pressing on ENTER. Use the UP or DOWN
arrow key to change each digit. Press ENTER to move the cursor to the right. When done, press
ENTER to save the value.

Press MENU twice to fully exit the menu.

Water activity (mode settings)

Setting

Applies to

Notes

Dwell Time

AwQuick

The HP23-AW waits the specified amount of time before
processing the humidity data with the AwQuick algorithm.
Recommended value: 3 or 4 minutes

AWQ-Temp

AwQuick

The HP23-AW considers temperature to be stable when the rate
of change of the temperature signal is less than the speciﬁ ed
value. Recommended value: 0.01 °C / min.

AWE-Temp

AwE

The HP23-AW considers temperature to be at equilibrium when
the rate of change of the temperature signal is less than the
speciﬁ ed value. Recommended value: 0.01 °C / min.

AWE-Humi

AwE

The HP23-AW considers humidity to be at equilibrium when the
rate of change of the humidity signal is less than the speciﬁ ed
value. Recommended value: 0.0001 Aw / min.

Preparation of the product samples
The HC2-AW probe may be used with two different sample cups.
(WP14:14mm deep/ WP-40: 40mm deep), which accept the respective one-way sample cups.
(PS-14: 14mm deep / PS-40: 40mm deep). In order to calibrate the probes with the certiﬁ ed
ROTRONIC humidity standards, only the shallow type should be used. Use the 14 mm cups for
liquids, powders, or paste; the deep ones are preferably used for coarse grained bulk goods.

The one-way sample cups serve two purposes:
a) As container for acclimatisation of the samples before measuring
b) Prevention of cross contamination with other samples. Fill a few of the one way sample
cups with the material that is to be measured.

Fill-Linie

PS14

PS40

To prevent cross-contamination, do not ﬁ ll over the ﬁ ll-line.

Further basic instructions
To make sure you get precise and repeatable results, please do follow the instructions below:
• Water activity should be measured only in temperature-stabilized rooms. Do not place the ar-

rangement near a heater or an open window. Avoid to expose the arrangement to direct sunlight.

• Fill the material samples into the one way sample cups and put the cover on it. The samples

should be stored in the same climatic environment as the probes. Let the samples acclimatize
to the room conditions. An often made mistake is to measure samples that have been stored
overnight in a refrigerator, without letting the material acclimatize. Neither should samples be
measured that come directly from the production line. When water activity is to be measured
at another than room-temperature, both probe and samples should be placed in an incubator,
which allows to set the desired temperature precisely.

• Avoid warming up of probe, sample cup and sample material by touching with your hands. Do

not hold for longer time than necessary!

• If you use an HC2-AW probe, please check whether or not the probe is switched on. This is

normally the case, when the probe is connected to the HP23-AW and the instrument is powered
up. The red LED on the top cover of the probe is blinking when the probe is powered. The probe
is not working and the instrument will not get a signal when the LED is not blinking. If necessary,
switch the probe on by pressing the red button.

Using the AwQuick measurement option

The HP23-AW uses an algorithm to project the full equilibrium value (water activity) of the product
sample:
• The value of the humidity signal is constantly monitored.
• The stability of the temperature signal is constantly monitored.
• After an initial period of time (dwell time), the humidity data is used to project the end value

of the equilibration process (water activity). The measurement ends automatically as soon as
the projected Aw value is stable. At that time, the HP23-AW freezes the display.

The measurement is automatically ended and typically requires about 5 to 6 minutes. With the
default dwell time of 4 minutes, the difference between the AwQuick mode and full product equi-
librium is typically 0.005 aw or less. The value of the dwell time can be set by the user. This value
represents a trade off between speed of measurement and accuracy. Generally, a longer dwell time
produces more accurate results but causes measurements to take longer. The value of temperature
shown at the end of the measurement is the average temperature during the measurement. The
HP23-AW displays a trend indicator to the left of the temperature value. This is used to verify that
temperature was stable during the measurement.

NOTES
• The measurement starts simultaneously for both probes
• Usually, the measurement ends at a different time for each probe
• Each probe can be displayed by using the UP or the DOWN key
• Do not press on ENTER until the measurement has ended for both probes
• The HP23-AW can be used with one probe only

1. AWQ Reset:
The HP23-AW is ready to start measuring either one or two probes.
When ready to measure, press on the ENTER key.

2. AWQ Dwell:
The measurement is in the “dwell” phase.

Current humidity value

Current temperature value

Elapsed time, hh:mm:ss

Probe 1 is being displayed

AwQuick mode is in
the dwell phase

3. AWQ Running:
At the end of the “dwell” phase the HP23-AW starts projecting the end result.

Current Aw projection

Final Aw projection

Average temperature

Measurement ended

4. AWQ Ended:
When the projection is stable for the probe being displayed, the HP23-AW automatically ends the
measurement and freezes the display for that probe. When measuring with two probes, use the
UP or DOWN key to verify the status of the other probe. Do not press ENTER until the measurement
is ended for both probes.

5. AWQ Reset:
Write down the measurement for each probe and press ENTER.
The HP23-AW is ready to start a new measurement.

Using the AwE measurement option

The HP23-AW monitors the water activity and temperature values. When both values are at
equilibrium during a few minutes, the measurement is automatically ended. Depending both on
the product being measured and on the stability of temperature, measurements typically require
30 to 60 minutes.

1. AWE Reset:
The HP23-AW is ready to start a measurement using one or two probes.
When ready to measure, press on the ENTER key.

2. AWE Running:
The HP23-AW starts monitoring the humidity and temperature signals for equilibrium.

Current humidity value

Current temperature value

Elapsed time, hh:mm:ss

Probe 1 is being displayed

AwE mode is running

3. AWE Ended:
When both the humidity and temperature signals of the displayed probe are stable, the HP23-AW
automatically ends the measurement and freezes the display for that probe. When measuring with
two probes use the UP or DOWN key to verify the status of the other probe. Do not press ENTER
until the measurement is ended for both probes.

Final Aw measurement

Measurement ended

HP23-AW calibration and adjustment procedures in general
Details for calibration of the HC2-AW probe are mentioned in the short instruction manual of the
HC2-AW probe.

The HP23-AW offers two distinct and separate procedures:
1) Acquisition and capture of calibration points to the memory of a probe or device
2) Adjustment of the probe or device based on the calibration points present in the

probe or device memory

1) The HP23-AW can be used to do a 1-point or multi-point calibration of up to two probes, trans-
mitters or other devices equipped with a UART interface, against a reference known environment.
Expose the device to be calibrated to the same known environment and wait for full equilibrium with
the environment. In a still air environment, it is highly recommended to provide some ventilation
that is common to the devices being calibrated.
• Press the MENU key and select either “Probe 1” or “Probe 2”.
Press ENTER to activate the Probe 1 or Probe 2 menu item.
• Use the DOWN arrow key to select either “Humi Adjust” or “Temp Adjust” (this can be done in

any order).

• Press ENTER to conﬁ rm and open the next sub-menu. Use the DOWN arrow key to select the

“Acquire (Enter Ref)” menu item and press ENTER to conﬁ rm.

Humi Adjust:
the HP23-AW displays both the current humidity read by the device to be calibrated and the
reference humidity (known environment). Press ENTER to activate the reference value menu item
and use the UP or DOWN arrow key to change each digit. Press ENTER to move the cursor to the
right. When done, press ENTER to save the value. Use the DOWN arrow key to select <Acquire>.
Press ENTER to activate the Acquire function. Press ENTER to conﬁ rm and save the calibration point
to the device memory. The HP23-AW automatically exits the menu.

Temp Adjust:
The HP23-AW displays both the current temperature read by the device to be calibrated and the
reference temperature (known environment). Press ENTER to activate the reference value menu
item and use the UP or DOWN arrow key to change each digit. Press ENTER to move the cursor to
the right. When done, press ENTER to save the value. Use the DOWN arrow key to select <Acquire>.
Press ENTER to activate the Acquire function. Press ENTER to conﬁ rm and save the calibration point
to the device memory. The HP23-AW automatically exits the menu.

Note:
The procedure can be repeated with different reference environments so as to accumulate several
calibration points (temperature: maximum 2 points, humidity: maximum 100 points).

After capturing all the calibration values the device must be adjusted by doing the following steps:

2) Adjustment of humidity and temperature
• Press the MENU key and select either “Probe 1” or “Probe 2”. Press ENTER to activate the Probe

1 or Probe 2 menu item.

• Use the DOWN arrow key to select either “Temp Adjust” or “Humi Adjust” (we recommend

selecting Temp Adjust ﬁ rst).

The following steps are the same for a temperature or a humidity adjustment
• Press ENTER to conﬁ rm and open the next sub-menu.
• Optional: with the “Acquired Points” menu item selected press ENTER and review the calibration

points present in memory. This submenu allows you to delete unwanted calibration points.
Press MENU when done.

• Use the DOWN arrow key to select the “Adjust” menu item and press ENTER to conﬁ rm.
• Press ENTER to activate the Adjust function. This function automatically erases the calibration

points in memory. When done adjusting, the HP23-AW automatically exits the menu.

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