What is water activity? 
Water activity is the measurement of water vapor pressure generated by the free or non-chemically bound water in foods and other products. The bound water and moisture content cannot be measured directly with this method. 

The Aw value (range: 0.00...1.00 aw) is an important indicator for the shelf life of foods, pharmaceutical and cosmetic products and it strongly influences the occurrence and growth of micro-organisms. The free water in a product influences its microbiological, chemical and enzymatic stability. 

This is of great importance especially for perishable products such as foods, grains, seeds and particularly for pharmaceutical powders and tablets. If there is too much free water, the food is spoiled. Too little water can adversely affect product properties. 


The new station probe HC2-AW-USB offers new possibilities. The USB probe can be directly connected to a PC running HW4-P-QUICK-Vx software enabling water activity measurement capability. The HC2-AW-USB is the perfect device for a multi station application, as multiple probes can be attached to a single PC.

USB station probes
USB probes can be ordered as single probe or as a set including the HW4 software with Aw Quick function. The set offers all possibilities to measure water activity.

  • Complete set of probe and HW4 including Aw Quick function available 
  • Measurement range: 0.00…1.00 Aw (0…100 %RH), -40…85 °C (-40..185 °F) 
  • USB interface for direct connection to a PC (HC2-AW-USB)


The insertion probe is suitable for measurement in dust-free bulk materials, bricks, concrete, etc. It measures humidity and temperature and calculates the dew/frost point.

Water activity measurement, mobile measuring units with handheld instruments and data loggers

  • Range of application: -40…85 °C / 0…100 %rh
  • Digital interface (UART) and scalable analog outputs, 0…1 V
  • Standard output scaling: 0…1 V = -40…60 °C / 0…100 %rh
  • Adjusted at 23 °C and 10, 35, 80 %rh

HygroLab C1:

ROTRONIC provides a high-end laboratory device – the HygroLab C1 – for water activity measurements with up to four probes. Connect station probes and insertion probes for measuring water activity in cheese, meat, tobacco, building materials, animal feed, pharmaceuticals products and much more.

Validated software
Easy-to-use and intuitive, the laboratory grade indicator can be used by anyone. HW4 running on a PC provides remote monitoring with charting and data recording functions.

  • 4 input channels for HC2 station probes or HC2 insertion probes can be connected for measurement of water activity, relative humidity and temperature 
  • Aw Quick function for fast measurement results (typically 4-5 minutes) 
  • Audible alarm to indicate completed measurement 
  • Saves up to 2,000 data records with %RH, °C/°F, date and time