- 1 SETUP
- 2 SPECIFICATIONS
- 3 RUNNING A TEST
- 4 PERFORMANCE VERIFICATION
- 5 CLEANING
- 6 TROUBLESHOOTING
- 7 CUSTOMER SUPPORT
- SKALA CONTROL TRAINING VIDEOS
- SKALA SYSTEM USER GUIDE (PDF)
The AQ2 is a water activity meter controlled and operated through the SKALA Hub touch interface. For more information on SKALA, please contact Customer Support.
Follow the instructions below to set up an AQ2 unit.
Figure 1 SKALA Hub front view
- Place the SKALA Hub and AQ2 on a clean, level surface in a location where the ambient temperature remains relatively constant.
The AQ2 should be well away from all heating and air conditioning vents, open windows, outside doors, refrigerator exhausts, and other sources of temperature fluctuation.
- Plug the SKALA Hub power cable into an electrical socket.
- Wait for the SKALA Hub login screen to appear.
- Enter SKALA login credentials.
If SKALA is not set up, please contact Customer Support.
- Connect the USB A to B cable into the AQ2 USB B port located on the back of the unit (Figure 2).
Figure 2 AQ2 rear view
- Connect the female end of the 3-prong power cable into the power port on the back of the AQ2 (Figure 2).
- Plug the USB cable from the AQ2 into the USB A port located at the back of the SKALA Hub (Figure 3).
NOTE: The AQ2 power cable and USB A to B cable are provided.
Figure 3 SKALA Hub rear view
|Operating Temperature||25 ℃|
|Temperature Resolution||0.1 ℃|
|Sample Dish Capacity||7.5 mL recommended (15 mL full)|
|Measurement Time||typically ≤5 min|
3 RUNNING A TEST
SKALA Hub handles the entire interface for setting up and taking readings with the AQ2. User, instrument, and product information must be set up in SKALA Control before acquiring traceable readings. Please refer to the SKALA System training documents and videos for more information.
Always use the following clean sampling practices to ensure accurate and repeatable readings.
NOTE: Before testing a sample, ensure that the AQ2 has warmed up for at least 30 minutes and that the sample chamber and cover are clean and dry.
NOTE: SKALA Hub will prompt the user to verify the calibration of the AQ2 according to the frequency established by the administrator in SKALA Control.
- Wash hands thoroughly or put gloves on prior to using the instrument.
- Fill the sample cup (Figure 4) enough to cover the bottom but no more than half full.
Figure 4 Sample cup
- Clean the bottom, sides, and rim of the sample cup thoroughly with KIMWIPES® strips (Section 5).
NOTE: The sample chamber is where the sample cup is placed in the drawer when the drawer is open. The measurement chamber of the sensor block describes the location where the sample cup resides when the drawer is closed (Figure 5).
Figure 5 Measurement chamber view of sensor block
- Select the appropriate test on the SKALA Hub screen (Figure 6).
Figure 6 SKALA Hub screen
The AQ2 will show a spinning blue light (Figure 7), indicating that the system is ready to collect a reading.
Figure 7 AQ2 front view
- Place the sample cup in the sample chamber:
a. Pull the AQ2 sample drawer out.
b. Lift the sample cover.
c. Place a sample cup (without the sample cup lid) into the sample chamber in the AQ2 drawer (Figure 8).
Figure 8 AQ2 sample drawer
- Lower the sample cover down over the sample cup, and push the drawer closed.
- Turn the drawer knob counter-clockwise to the Closed position to begin the reading.
The light will spin clockwise, indicating the knob should be turned towards the Open position when the reading is finished. The AQ2 will start the reading, and the light on the front will pulse slowly.
If a test has not been selected from SKALA Hub, one can be chosen now by selecting sample already loaded, begin test option.
NOTE: Do not turn the drawer knob or open the drawer before the test has completed. This will cancel the test.
- When the test is finished, the indicator lights will show a solid color corresponding to the reading received (Figure 9).
a. Solid green indicates the reading is within defined operational limits.
b. Solid yellow indicates the reading is outside of defined operational limits but within defined fail limits.
c. Solid red indicates that the reading is outside of defined fail limits.
d. Flashing red indicates there is an error associated with the AQ2 block. SKALA Hub should indicate what the error is and how to fix the error. If the error is not actionable by the user, the message will be to contact Customer Support.
See Section 6 for information on what to do if the indicator light is red.
Figure 9 AQ2 indicator lights
- Turn the drawer knob clockwise and open the drawer.
The water activity, temperature, date, and time will be automatically saved in SKALA Control with the associated product batch (Figure 10).
Figure 10 SKALA Control screen
The AQ2 reports the reading when equilibrium is reached; for many products, equilibrium will occur in 5 minutes or less. However, some types of products may take longer, such as products with
- a moisture barrier (e.g., whole seeds and nuts),
- a high fat content (e.g., peanut butter),
- extremely low water activity, or
- multiple components (e.g., cakes with filling, cheese and crackers, cereal with fruit).
Contact Customer Support to help verify whether or not the product requires longer read times and if there are options to make the read time shorter.
4 PERFORMANCE VERIFICATION
Verification tests to validate instrument accuracy should be performed once per day or once per shift when the AQ2 is in use. Verification schedules and the selection of verification standards to use can be set in SKALA Control.
Verification is achieved using verification standards supplied by METER. METER recommends using a standard whose water activity most closely matches that of the samples to be tested. For example, if a set of products to be tested were in the range of 0.650 to 0.850 aw, the verification standard to use would be the 0.760 standard. SKALA Hub will display prompts to run a verification according to the set schedule and using the specified standards.
When the SKALA Hub indicates a verification is needed, follow the steps below.
- Wash hands thoroughly or put on lab gloves.
- Ensure the sensor block and drawer are clean (Section 5).
- Select the standard specified on the SKALA Hub.
- Check the expiration date of the standards solution.
The typical shelf life of standards is 1 year. Expired standards should not be used for verification.
- Remove the cap on the vial by twisting counter clockwise.
- Empty the contents into a sample cup. The standard should cover the bottom of the cup.
Do not contaminate the sample chamber by spilling standard inside the sample chamber.
- Take a reading (Section 3).
- Check SKALA Hub for results. It will ask if the user wishes to apply an offset.
a. If the reading is within ±0.005 aw of the standard value, the calibration has been verified, and the AQ2 is ready to begin taking readings.
b. Apply an offset only if the reading is near the outer limits of the specifications (i.e., ±0.003-0.005 aw).
- If the reading is more than 0.005 aw off, SKALA Hub will display instructions to clean the AQ2 and retry the verification.
It is extremely important to keep the instrument clean to make sure it is performing accurately. It should be cleaned when contamination is seen. However, some types of contamination are not visible. The best way to check for contamination is by running verification standards daily or at the start of each shift. If the verification standards are not within specification, cleaning the AQ2 sensor block is recommended. The AQ2 comes with a cleaning kit that contains the following items:
- Sample cups
- Sample cup lids
- Cleaning swabs
- KIMWIPES strips (1.25 in)
- Cleaning solution (in bottle with white lid)
- Deionized water (in bottle with blue lid)
NOTE: Regulations regarding hazardous materials prevent METER from shipping isopropyl alcohol in the cleaning kits, but it is often the best cleaning agent, particularly when measuring samples with a high fat content.
Use the following process to clean the AQ2.
- Unplug the AQ2 from power and the SKALA Hub.
- Put on lab gloves.
- Wipe the drawer and detachable sample cover clean, making sure no sample residue remains on the drawer.
Ensure that the sample cover and drawer are thoroughly dried prior to continuing operation.
- Lift off the top of the AQ2 to expose the interior (Figure 11).
Only the sensor block and ribbon cable will be visible.
Figure 11 AQ2 with top removed
- Pull out on the side tabs to unplug the ribbon cable.
- Loosen the thumbscrews and lift sensor block to remove (Figure 12).
Figure 12 AQ2 with sensor block removed
- Turn the sensor block over so the sensor chamber area is visible, and clean the sensors and sensor block.
a. Wrap a KIMWIPES strip around a cleaning swab by folding the wipe over the head and twisting the swab until reaching the end of the strip.
Click on Figure 13 below to view a video showing how to wrap a KIMWIPES strip around the cleaning swab.
NOTE: Fully cover the cleaning swab with the tissue to avoid scratching the components and surface of the chamber.
Figure 13 METER Cleaning kit
b. Moisten the KIMWIPES strips with cleaning solution or isopropyl alcohol (concentration greater than 90% recommended).
To avoid contamination, do not dip a used KIMWIPES strips into the cleaning solution or alcohol.
c. Clean the mirror and optical sensor by gently wiping the KIMWIPES strips over the sensors (Figure 14).
NOTE: Do not put too much pressure on the thermopile sensor, the mirror, or optical sensor.
Figure 14 Bottom view of sensor block
Discard used KIMWIPES strips frequently during the cleaning process to get each component clean.
NOTE: It is important to use the KIMWIPES strips supplied in the cleaning kit rather than facial tissue, paper towels, or commercial swabs. KIMWIPES strips are specially made for lab work. They do not contain adhesives or other contaminants and are made from low-lint fibers that will not scratch delicate surfaces when wet.
d. With additional moistened KIMWIPES strips, clean the remaining surfaces of the testing block without wiping the KIMWIPES strips back over the sensors.
- Moisten a fresh KIMWIPES strip wrapped around the cleaning swab with deionized water.
- Clean the sensors and sensor block, following the same procedure outlined in step 7. To avoid cross-contamination, do not dip used KIMWIPES strips into clean distilled water.
- Use fresh dry KIMWIPES strips wrapped around the cleaning swab to remove moisture on the sensors and in the sensor block.
PROBLEM: The device does not appear on the SKALA Hub main screen.
- Make sure all cables and connectors are properly connected and the power indicator is in the On position.
- Disconnect and reconnect the device. If it still does not appear, contact Customer Support.
PROBLEM: Readings are slow or inconsistent.
- The sample chamber may be dirty.
Clean the instrument according to instructions (Section 5).
- The temperature difference between the sample and the instrument may be too large.
The sample needs to equilibrate to instrument temperature before an accurate reading can be made. This can be done by letting the sample sit in a covered sample cup for a time. Covering the sample minimizes exposure to ambient humidity, which can affect the water activity of the sample. Samples can also be equilibrated to a specific temperature with a Temperature Equilibration Plate, which can be purchased from METER.
- The product sample may be low emitting.
Some products absorb or desorb moisture very slowly, causing measurements to take longer than usual. Although these samples will always take longer to come to vapor equilibrium inside the sample chamber, Customer Support can provide strategies to help speed up read times.
PROBLEM: The device is not reading correctly.
- Make sure that clean sampling practices (Section 5) are being followed and that standards solutions have not expired.
- Check if the product being tested has special properties that need special consideration. Volatile compounds will affect the water activity readings of the AQ2. If products being tested contain volatiles, contact Customer Support for further assistance.
- Verify that the o-ring is seated properly by removing the sensor block and inspecting it.
- Keep samples in sealed packaging or in a sample cup with a sample cup lid when a sample is not actively being read. Otherwise, the sample water activity will slowly equilibrate with the humidity in the ambient air.
NOTE: If the sample will be sitting for more than 2 hours before being read, seal the sample cup edges with a piece of parafilm or a similar material.
Most instrument problems are directly related to contamination in the sensor chamber. Refer to Section 5 for instructions on cleaning the instrument.
7 CUSTOMER SUPPORT
Customer support representatives are available for questions, problems, or feedback Monday through Friday, 7 am to 5 pm Pacific time.
If contacting METER by email, please include the following information:
|Address||Instrument serial number|
|Phone number||Description of problem|
NOTE: For instruments purchased through a distributor, please contact the distributor directly for assistance.
KIMWIPES® is a registered trademark of Kimberly-Clark Worldwide, Inc. Used with permission.