Can I reuse the standards or sample cups?
The standards we use are unsaturated salt solutions, which are created with high accuracy and precision. They are not reusable, however, as exposure to ambient conditions will begin to alter the standards. If they are kept in a sample cup with a lid, they can be kept for up to two hours but no longer. The sample cups are meant to be disposable. Residue left behind from the previous sample can impact your readings and introduce error. Repeat washing of the cups breaks down the coating and material can become embedded in the plastic, which can also introduce error. For consistent and accurate results, we do not recommend reusing the cups.
Re-order sample cups and standards →
What standards should I use to verify?
You should always select two standards that bracket your product range. A two-point verification is necessary to evaluate the factory calibration and ensure the slope is correct.
To ensure the instrument is reading correctly across your product range, and to satisfy audit requirements, select two standards that bracket or are closest to your working range for routine verification. We offer seven standards that cover a broad range of water activity values.
Why do I get long read times?
Long read times could be caused by a number of factors. The four most common causes are listed below.
1. The most common is that the instrument needs to be cleaned. Lack of cleaning or improper cleaning frequently causes long read times.
2. Sample type: High fat, viscous and low water emitting samples all take longer to equilibrate in the chamber. This is sample dependent and long read times are necessary to give accurate, fully equilibrated results.
3. Volatile ingredients such as alcohols, propylene glycol, and acetic acid can interfere with the chilled mirror sensor and cause unstable readings and extended read times.
4. A damaged or bent fan blade in the chamber. If the fan is damaged and not working correctly, the removal of boundary layer moisture on the mirror surface is delayed, extending the read times.
How often should I run the verification standards?
This will depend on the frequency of use and the environment the instrument is operating in. If the instrument is being used daily, we recommend a daily verification prior to running samples. If the instrument is used sporadically, verifications on the day of use are sufficient. In manufacturing environments that are dusty or greasy, involve samples that are messy, or running multiple shifts per day, the verification may need to be done each shift. This is particularly important if water activity is part of a release specification.
How often should my instrument be sent in for service?
We recommend that instruments come in once per year for annual service and calibration. This is required if you must have a certificate on file showing instrument calibration. If the instrument is used heavily and in harsh environments, more frequent service may be needed.
