Portable water activity meter for food and materials
A professional water activity meter (aw value) with a data logger for quality control, shelf life and product safety in food and other materials. A laboratory instrument in line with EN ISO 21807.
The humimeter RH2 measures the amount of free water (water activity) in products such as butter, fruit mixes, spices, granulates, mushrooms, xylitol, flour, biscuits, sausage, PVC granulate and many more. With additional sensors it also checks climatic conditions in warehouses and rooms.
Two sensor versions are available: a large measuring chamber for bigger samples and more random measurements, and a small measuring chamber for very small quantities, with an exchangeable sensor. Both equalise quickly and use sensors that stay stable over the long term.
Please note: the device is not suitable for juices, syrups, acidic products such as vinegar, or food and beverages containing alcohol.
Main features
- Water activity range: 0.03 to 0.99 aw; resolution 0.001 aw
- Calibration: 0.10 to 0.80 ±0.01 aw (at 25 °C); end ranges ±0.04 aw
- Temperature: 0 to +50 °C; resolution 0.1 °C; calibration ±0.5 °C (at 25 °C)
- Relative humidity: 0 to 100 % RH; resolution 0.1 % RH
- Dew point: -55 to +60 °C; resolution 0.1 °C
- Absolute humidity: 0 to 130 g/m³; resolution 0.1 g/m³
- Equilibrium moisture content of wood (EMC): 2 to 30 %; resolution 0.1 %
- Equilibrium moisture content of synthetic granulates: resolution 0.01 %
- EMC curves programmable by the user
- Online function, hold function, automatic data logger for 10 000 readings
- Menu languages: English, German, Italian, French, Spanish, Portuguese, Czech, Russian, Polish and others
Your benefits
- aw measurement plus relative and absolute humidity, dew point and equilibrium moisture content
- Fast equalisation and sensors that stay stable over the long term
- Readings stored and archived directly in the device
- Data analysis in LogMemorizer and printed reports
- Professional documentation of quality and compliance
- Portable, accurate, supported for the lifetime of the device
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Article no. 12005 - humimeter RH2 water activity meter
Extended accessories
- Art. no. 13700 - aw measuring chamber with humidity and temperature sensor (2 m cable); supplied with 2 jars of 186 ml, 2 jars of 245 ml, 4 lids, calibration ampoules (art. no. 10005), factory certificate (art. no. 10403) and a case (art. no. 13624)
- Art. no. 14500 - aluminium small aw measuring chamber 25 ml with sensor (2 m cable); supplied with 8 PP inserts of 25 ml, calibration ampoules (art. no. 10005), certificate (art. no. 10403) and a case (art. no. 13624)
- Art. no. 13741 - jar replacement set with twist-off lid, 14 units, max. 186 ml
- Art. no. 13740 - jar replacement set with twist-off lid, 14 units, max. 245 ml
- Art. no. 14126 - set of 14 plastic containers with twist-off lid (max. 200 ml) for the aw measuring chamber
- Art. no. 12278 - USB interface with LogMemorizer software and USB cable for the PC
- Art. no. 14944 - internal Bluetooth 5.0 module with LogMemorizer basic software for recording and analysing measured data
- Art. no. 15444 - thermal printer with rechargeable battery (USB-C version) - portable serial printer for humimeter devices with a USB interface
- Art. no. 10005 - certified calibration ampoules, set of 5 (2 × 35 %, 1 × 50 %, 2 × 80 % RH)
- Art. no. 10352 - certified calibration ampoules, set of 5 at 50 % RH
Handling and measurement process
Fill the material into the measuring chamber and close it. After the conditioning time, which ranges from about 5 minutes to roughly one hour depending on the material and the temperature, read the aw value directly from the display. Equilibrium can be assumed once the reading is stable, that is when it changes by less than 0.002 aw over 10 minutes. Samples should be close to the temperature of the device - a large difference makes the process longer, and that is physics rather than something the device can shorten.
Calibration and adjustment
Calibrate regularly with certified ampoules at 35 %, 50 % and 80 % RH; a detailed calibration instruction is available. The recommended temperature range is 20 to 26 °C, ideally 23 °C. If the deviation exceeds 1.5 % RH, adjust the device in its menu, after unlocking the settings with the password, which is the serial number.
Frequently asked questions
- What is water activity (aw)?
It is a measure of the free water in a product and it decides how fast micro-organisms grow. The scale runs from 0 to 1: high aw means faster spoilage, low aw means longer shelf life.
- How does water activity (aw) relate to equilibrium relative humidity (ERH / % RH)?
Water activity is exactly the same physical quantity as equilibrium relative humidity, only expressed on a different scale.
The two scales:
1. aw - range 0 to 1 (for example 0.75 aw)
2. % RH - range 0 to 100 % (for example 75 % RH)
The conversion:
aw = % RH / 100
Why does the calibration certificate state % RH?
1. The RH2 sensor measures the relative humidity of the air in the chamber above the sample once equilibrium is reached.
2. Calibration laboratories work with certified standards, that is climatic chambers, on the % RH scale.
3. Accreditation to ISO 17025 is issued for relative humidity only.
4. In aw mode the meter simply divides the result by 100 and shows it on the 0 to 1 scale.
That is why the certificate always shows % RH while the display shows aw. It is the same physical value on a different scale.
- Why does water activity matter in the food industry?
It governs shelf life, keeps mould and bacteria away, and supports consistent quality and compliance with standards.
- Is the RH2 suitable for meat?
Yes. Fresh meat has a high aw value; curing and drying lower it and extend the shelf life.
- What is the right aw value?
It depends on the product - manufacturers set their own limits for microbiological safety.
Contact us
Interested in the humimeter RH2 water activity meter? Get in touch for more information, a quotation or individual advice.
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