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Water Activity Tips and Tricks

Water Activity Measurement FAQ

What are the sensor filters used for and how do I choose the right one?
These specially designed filters shall be mounted in front of the sensor and used to provide protection against chemical contamination and degradation of the resistive electrolytic sensor element. As the inner part of the sensor consists of a liquid, volatiles which dissolve and dissociate are extremely dangerous and harm the sensor in a very short time. Be aware that sensor failure due to chemical contamination by NOT using an appropriate chemical filter is not covered by warranty and replacement goes 100% on the user's account. We have a filter selection chart that we can provide to help you decide which filter is best for your samples.
How often should I replace my filter?
  • If you do less or equal than 10 measurements a week, change filter every 6-12 months
  • If you do more than 10 measurements a week, change filter every 3-6 months
  • If instrument is in use, day and night, change filter every 2 months

Please read the operating instruction manual of the water activity meter as well to learn about the procedure how to find out the optimal chemical filter changing interval. It is important that the filter is changed from time to time as it is of saturation type. Once saturated, volatiles will pass through and harm the sensor. Be aware that sometimes filter combinations must be used to get highest protection efficiency. As soon as ethanol is involved, our alcohol-resilient sensor (CM-3 or awSens-ELS) must be used. If ethanol is present in conjunction with other volatiles, select the alcohol-resilient sensor plus the respective filter(s) from the selection list. Note that chemical filters will extend the measurement time as the water vapor has to pass through the filter but it will not affect the measurement value. If you have doubts about the procedure or feel unsure how to work that out, please do not hesitate to contact us.

What exactly is a PM and why should I consider it?
A PM (Preventative Maintenance) is a proactive measure taken to ensure that your unit does not suffer any damage due to preventable issues caused by wear and tear and that is continues to run like new for years to come. A PM is completed by performing a full "tune up" of the unit, which includes full diagnostics, calibration, replacement of pre-filters, internal sterilization, cleaning and certification.
How often should I calibrate my instrument?
It is recommended that you perform daily/weekly verifications by placing a SAL-T standard in the measurement chamber, just like you would a cample. If the stable reading is not within range of the theoretical value, a calibration should be performed. Remember to use at least 2-3 SAL-T standards for a bracket calibration around your typical sample range. Additionally, we recommend sending in your instrument annually for a PM and calibration.
Why do I need temperature control?
Temperature control assures higher accuracy results, provides a constant equilibrated environment for repeatbale testing and complies with requlatory testing that is carried out at 25°C.
How long are the calibration standards good for?

Calibration standards are reusable with a shelf life of 2-4 years, depending on factors such as storage conditions (storage container must be closed properly), frequency of use, exposure to light, and the value of the standard.