ROTRONIC HC2-AW-USB - Manual (Page 8)

E-M-HC2-AW-USB-V1_11
Rotronic AG
Bassersdorf, Switzerland
Document code Unit
Water Activity and Temperature Probe
HC2-AW-USB: User Guide Instruction Manual
Document Type
Page 8 of 18
Document title
© 2011-2012; Rotronic AG E-M-HC2-AW-USB-V1_11
5.2.1 Additional guidelines
a) Measure water activity only in a temperature stable area. This is an essential requirement! Do not measure
on a bench that is located near a heater, an AC vent or an open window. Avoid direct exposure of the probe
and/or product samples to sun light (heating effect). For best accuracy, temperature should not change by
more than 0.01
°C / minute (0.0075 °C / minute in the case of product with a water activity > 0.80 aw)
b) Prior to measurements, place each product sample in a disposable sample cup with the cover on. Place the
cups in the same general area as the probe. Allow for sufficient time for the samples to come to the
temperature of the probe (usually room temperature). A frequent mistake is to measure product samples
which have been kept overnight in a refrigerator without first allowing them to come to room temperature.
Another mistake is to measure samples coming straight from a hot manufacturing process. To measure water
activity at a temperature other than room temperature, place both the probe and the product samples in an
incubator set at the desired temperature.
c) Prior to using the probe, verify the integrity and cleanliness of the sealing O-ring located under the probe
d) Avoid warming up the probe, the sample holder or the product sample by touching or holding for too long in
your hand.
5.3 Water activity measurement with HW4
5.3.1 Water activity measurement modes
The AwE / AwQuick tab is available only with HW4 Professional with AwQuick. HW4 features two modes for
measuring water activity and the name of the tab depends on which mode has been selected.
● AwE mode
In this mode HW4 monitors the stability of both temperature and humidity. The measurement is automatically
ended as soon as both humidity and temperature reach equilibrium. The natural (or static) equilibration of
most products typically requires from 45 to 60 minutes and can take as long as a couple of hours.
● AwQuick mode:
In the AwQuick mode, HW4 uses an algorithm to project the full equilibrium value (water activity) of the
measured product. The measurement is automatically ended and typically requires about 5 minutes.
HW4 performs the following tasks:
1) The value of the humidity signal is constantly monitored
2) The stability of the temperature signal is constantly monitored
3) After an initial period of time (dwell time), HW4 uses the humidity data to project the end value of the
equilibration process (water activity). The measurement ends automatically as soon as the projected
Aw value is stable.