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METER AQUALAB Manual

Vapor sorption analyzer
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VSA
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  • Page 1 AQUALAB ©...

  • Page 2: Table Of Contents

    13832-07 2.2022 TABLE OF CONTENTS 1. Introduction ....................1 2. About the VSA ..................2 2.1 Moisture Sorption Isotherms ..............2 2.2 Measurement Method................3 2.3 Specifications .................... 4 2.4 User Interface and Menus ................5 2.4.1 Isotherm Tab ..................6 2.4.2 Measurement Tab ................
  • Page 3 5.2.1 Cleaning Kit ................... 34 5.2.2 Cleaning Procedure ................ 35 5.3 Capacitance Filter Replacement .............. 36 5.4 Maintenance Packages ................37 6. Verification and Calibration ............38 6.1 Water Activity Verification ............... 38 6.1.1 Verification Standards ..............38 6.1.2 Verification of Calibration .............. 39 6.2 Linear Offset ....................
  • Page 4 9. Service ....................... 59 9.1 Troubleshooting ..................59 9.2 Customer Support..................64 9.3 Repair ...................... 65 9.4 Terms and Conditions ................65 Index ......................... 67...

  • Page 6: Introduction

    • Moisture Analysis Toolkit Software Package with registration key • 1 2-g NIST traceable weight • Tweezers NOTE: Please keep your original instrument shipping box. If the VSA needs to be returned to METER, it must be shipped in the original packaging.

  • Page 7: About The Vsa

    ABOUT THE VSA 2. ABOUT THE VSA The VSA Isotherm Generator is an automatic moisture sorption isotherm generator that can generate both dynamic and equilibrium moisture sorption isotherms. 2.1 MOISTURE SORPTION ISOTHERMS A moisture sorption isotherm defines the relationship between water activity (a ) and moisture content at a given temperature.

  • Page 8: Measurement Method

    METER’s patented chilled-mirror dew point sensor. The VSA imposes drying of the sample by flowing dry air from a desiccant tube across the sample and wetting of the sample by saturating the air with water before it enters the chamber to flow across the sample.

  • Page 9: Specifications

    ABOUT THE VSA 2.3 SPECIFICATIONS MEASUREMENT SPECIFICATIONS Water Activity 0.030–0.95 a Range (3%–95% RH) 0.0001 a Resolution (0.01% RH) ±0.001 a (0.1% RH) for volatiles setting Accuracy ±0.005 at 25 °C Temperature Range 15–50 °C Resolution 0.01 °C Accuracy ±0.1 °C Adjustment Increment 1 °C Read Time...

  • Page 10: User Interface And Menus

    EM ISO/IEC 17050:2010 (CE Mark) 2.4 USER INTERFACE AND MENUS The AQUALAB VSA is a standalone instrument with arrows and three buttons useful for navigating menus and beginning tests. There are four tabs at the top of the display screen, the Isotherm, Measurement, Configuration, and Data tabs.

  • Page 11: Isotherm Tab

    ABOUT THE VSA Table 1 AQUALAB VSA button icons Icon Name Action Enter Accepts the current action CANCEL Ends the current action Switches between the Isotherm, Measurement, Configuration, and MENU Data tabs SAVE Saves a setting or a reading Accepts the input from the user...

  • Page 12: Measurement Tab

    AQUALAB VSA 2.4.2 MEASUREMENT TAB The Measurement tab allows you to take water activity readings of the sample in the sample chamber when not running a test. Pushing the right or left arrow keys changes the display to a temperature equilibration screen that shows the temperature difference between the sample temperature and the lid temperature.
  • Page 13 ABOUT THE VSA 2.4.3.1 CALIBRATION Highlight “Calibration” and press the Enter button to open the Calibration menu where you can make either a water activity or weight adjustment. For more details on weight and water activity calibration procedures refer to Section 6. You may also reset the calibration to the factory defaults by highlighting the Defaults option in the calibration menu and pressing Enter.
  • Page 14 AQUALAB VSA 2.4.3.4 BASIS The VSA generates water activity values and corresponding sample weights during moisture desorption and resorption. To complete the isotherm, the sample weights must be translated into moisture contents. Moisture content can be calculated in different ways and reported with a variety of different units.
  • Page 15 ABOUT THE VSA 2.4.3.6 TIME Pressing Enter with the Time option highlighted allows you to set the current local time. Press the up or down arrows to change any of the individual values. Press the left or right buttons to change between hour and minutes. The hour setting automatically changes between AM and PM.
  • Page 16 AQUALAB VSA 2.4.3.9 TEMP EQ Temperature Equilibration Tolerance or “Temp Eq” sets the maximum difference allowed between the lid and the sample. This lid to sample temperature difference must be less than the Temp Eq in order to start a water activity measurement. If a sample is out of this range, the VSA waits for the sample to equilibrate prior to beginning the water activity measurement.
  • Page 17 Press Enter to toggle auto restart between on and off. METER recommends this be set to on to prevent data loss. Note: Restart tests with a new sample if power outages last more than 30 minutes.
  • Page 18 AQUALAB VSA Figure 10 External Gas screen to turn on gas To start using external gas, remove the external gas plug from the back of the VSA and insert the desired gas source. Adjust the external gas pressure until it is between 5 and 35 kPa (0.7 to 5 psi).
  • Page 19 ABOUT THE VSA Figure 12 External Gas screen to turn off gas 2.4.3.18 DIAGNOSTICS The Diagnostics screen provides you with detailed information about all the sensors in the instrument. Refer to Section 9.1 for details on what kind of values you should expect for each sensor.

  • Page 20: Data Tab

    AQUALAB VSA to the left, it switches to the left desiccant tube (#1). If you press the number button with the arrow to the right, it switches to the right desiccant tube (#2). Any time you press the desiccant tube button, the pump turns on and blows dry air into the chamber to monitor the desiccating capacity of the tubes.
  • Page 21 ABOUT THE VSA Figure 15 View data screen GRAPH SCREEN This selection shows a graph of the selected data from the previous screen. Press the directional arrows to change the y or x-axis units. The title of this graph indicates the test name, stage number (if applicable), and the isotherm type is on the right.
  • Page 22 AQUALAB VSA SUMMARY SCREEN This selection allows you to view your stored measurements. The up/down arrows move you through the stored data with the most recent measurements at the top of the table. You may also press the left and right arrows to page quickly through the data. While on the Summary screen, press the Enter button on a highlighted reading to get detailed information on the reading in the Data screen.

  • Page 23: Theory

    THEORY 3. THEORY Water profoundly influences product attributes such as quality and safety. To completely understand water relations in a product requires an understanding of the amount of water (moisture content) that can be held at a given energy state (water activity). Moisture sorption isotherms describe the relationship between water activity and moisture content at a constant temperature.

  • Page 24: Combining Dvs And Ddi In One Instrument

    3.1 COMBINING DVS AND DDI IN ONE INSTRUMENT A unique and important feature of the AQUALAB VSA is that it can generate both dynamic and equilibrium isotherms. As explained above, both DVS and DDI methods have advantages and disadvantages. While the data they generate agrees in some cases, it is the uniqueness of the results from each method that gives them value.

  • Page 25: Hysteresis

    THEORY as kinetics of sorption. Therefore, to provide the most information about the moisture characteristics of a material, both types of isotherms are needed. The VSA can provide both DVS and DDI isotherms and even run them both on one sample. 3.2 HYSTERESIS Figure 20 shows two isotherms, one obtained by wetting a sample from complete dryness...
  • Page 26 AQUALAB VSA Figure 21 Scanning adsorption Curves from drying to varying These observations help clarify the point that an isotherm is not a single valued function. The water content for any given water activity value depends on the wetting and drying history of the sample.

  • Page 27: Nonequilibrium

    THEORY Structural changes within a solid matrix occur when the material swells and polar sites once obscured are now exposed to bind with water. For example, hydrated protein contains many sites for water “binding” before desorption while dehydrated protein has limited polar sites for water binding prior to adsorption.

  • Page 28: Working Isotherms

    AQUALAB VSA Figure 22 Spray-dried milk moisture sorption isotherms 3.5 WORKING ISOTHERMS Full boundary isotherms give information about the physical characteristics of a product, show hysteresis, and are important in establishing critical control points, but in many cases a working isotherm proves very useful. A working isotherm shows how a product adsorbs and desorbs water from its current or typical condition.

  • Page 29: Isotherm Models

    THEORY Figure 23 Working and full isotherm for wood pulp 3.6 ISOTHERM MODELS Several different isotherm models have been proposed and compared in the literature. These models are necessary to predict the moisture content at a given water activity and are used to evaluate thermodynamic functions of water in foods.

  • Page 30: Uses For Moisture Sorption Isotherms

    AQUALAB VSA Where m is the moisture in g/100 solids or g/g solids, k is a constant in the range of 0.70 to 1 and c is a constant in the range of 1 to 2,000. In addition, m is the monolayer moisture content in the same units as m and a is the water activity at moisture m.
  • Page 31 THEORY Changes in the slope of the isotherm indicate phase transitions and can provide information about critical water activities for maintaining texture properties and preventing caking and clumping. You can also determine the water activity value where the glass transition temperature equals storage temperature or the crystallization temperature equals storage temperature.

  • Page 32: Installation

    AQUALAB VSA 4. INSTALLATION Please read all instructions before operating the AQUALAB VSA to ensure the instrument performs to its full potential. Please contact Customer Support at any time for assistance with installation and setup. PRECAUTIONS METER instruments are built to the highest standards, but misuse or neglect may damage the device and possibly void the manufacturer’s warranty.
  • Page 33 INSTALLATION Table 1 Installation (continued) Plug In Instrument Plug the power cord into the back of the unit and an outlet. Only use the supplied power cord or one rated for VSA and certified for the country of use. The cord must be a minimum of 18 AWG and have a rating for 10 A or greater.
  • Page 34 Shore up the table or find another location for the equipment. NOTE: Contact the AQUALAB distributor if the scale readings are unstable after placing the unit on a stable structure.
  • Page 35 Remove the USB drive. Connecting Plug in the USB cord into a Windows PC USB port and into the VSA COM port. Open the Moisture Analysis Toolkit Software. Select the METER USB COM port in the toolbar. Click Connect.

  • Page 36: Cleaning And Maintenance

    AQUALAB VSA 5. CLEANING AND MAINTENANCE Keeping the AQUALAB VSA clean is vital to maintaining the accuracy of the instrument. Dust and sampling debris can contaminate the sampling chamber, so regular cleaning is essential. Instructions for cleaning the VSA desiccant cartridge and the sample chamber are both in this section.
  • Page 37 CLEANING AND MAINTENANCE Figure 25 Desiccant cartridge foam Hold the small tubing at the top by curling the tubing over the top edge of the cartridge. This prevents desiccant from getting into it when emptying the cartridge. Pour out the desiccant material. Wash out the lid and washer.
  • Page 38 AQUALAB VSA Place in the foam at the top. Place the small tubing across the filter and through the slit in the foam (Figure 25). Wet the cartridge (bottle) lip and the edge of the washer adjacent to the bottle lip...

  • Page 39: Sample Chamber Cleaning

    CLEANING AND MAINTENANCE AQUALAB VSA uses a 10 to 20 mesh indicating drierite as the desiccant. Indicating drierite is not required but the size of a replacement desiccant must be 10 to 20 mesh. 5.2 SAMPLE CHAMBER CLEANING To clean the AQUALAB VSA, carefully follow these instructions and refer to the labeled...

  • Page 40: Cleaning Procedure

    5.2.2 CLEANING PROCEDURE The procedure to clean AQUALAB VSA involves washing, rinsing, and drying each area. Do not get cleaning solution on the capacitance sensor filter. Repeated exposure of cleaning materials or contaminants to the filter may cause inaccurate readings and the filter will need to be replaced (Section 5.3).

  • Page 41: Capacitance Filter Replacement

    If necessary, repeat the cleaning process using new KIMWIPES tissues. Let stand for 5 min to ensure the sample chamber is dry. After cleaning the AQUALAB VSA, check the instrument performance and correct for any linear offset that may have occurred during the cleaning process.

  • Page 42: Maintenance Packages

    AQUALAB VSA 5.4 MAINTENANCE PACKAGES METER offers maintenance and calibration packages to ensure AQUALAB is functioning to its highest standard (Table 3). Table 3 Maintenance package options Package Basic Calibration Service As-found inspection Available Replace old/damaged parts Separate charge per part Instrument cleaning...

  • Page 43: Verification And Calibration

    METER also recommends annual factory calibration to maintain optimal performance. 6.1 WATER ACTIVITY VERIFICATION The AQUALAB VSA uses both a capacitance relative humidity sensor and a chilled-mirror dew point technique to determine water activity. If you set volatiles to yes, the VSA performs water activity verification on the capacitance sensor only.

  • Page 44: Verification Of Calibration

    Remove the weighing pan. Empty a vial of solution into the stainless steel sample cup. Place it in the AQUALAB VSA testing chamber. Make sure that the standard is as close to the instrument temperature as possible. NOTE: Make sure the rim and outside of the sample cup are clean.
  • Page 45 Reread first Read second standard standard Go to offset Go to sampling procedure procedure Figure 29 Verification standard flowchart. A check indicates AQUALAB VSA verified the standard within specification; a cross indicates AQUALAB VSA did not verify the standard within specifications.

  • Page 46: Linear Offset

    Figure 31 Calibration instruction dialog Empty the whole vial of water activity standard into a sample cup. METER recommends using the 6.00 NaCl (0.76 a ). Do not adjust for the offset using steam distilled water.

  • Page 47: Adjusting For Weight Measurement Offset

    NOTE: To interrupt the offset procedure, return the lever to the OPEN position or select CANCEL to return to the previous screen. After the AQUALAB VSA has finished measuring the verification standard, it displays a Change the offset screen (Figure 32).

  • Page 48: Restore Factory Defaults

    AQUALAB VSA Figure 34 Calibration: Weight screen Highlight start and press the Enter button. Follow the wizard on screen commands. When asked to place the 2-g weight on the balance, handle carefully with tweezers and gloves to prevent changing the weight of the standard.

  • Page 49: Isotherm Standard Comparison

    This can only be done using the Moisture Analysis Toolkit software and must be performed on Microcrystalline Cellulose (MCC). METER included a sample of MCC with the instrument or you can use your own lab grade MCC. Contact Customer Support if you need additional MCC samples.
  • Page 50 AQUALAB VSA sample size of 1 g when running the MCC standard test. An error value less than 0.12 would be acceptable. If the error value is greater or equal to 0.12, contact Customer Support additional assistance. If you disconnect the Moisture Analysis Toolkit software at any time while running the standard test, it does not automatically generate a comparison.

  • Page 51: Running A Test

    7. RUNNING A TEST 7.1 BECOMING FAMILIAR WITH STAGES The AQUALAB VSA uses test stages to maximize the utility of running an isotherm test. In the vocabulary of setting up and running moisture sorption isotherms with the VSA, an isotherm test is considered a collection of stages all performed on one sample.
  • Page 52 AQUALAB VSA Before starting a test, set the Volatiles: Yes/No option in the Configuration menu. If the sample has volatiles, select Yes otherwise select No. On the Main screen, select the Test Wizard. The Warning screen appears to let the user know that any data points currently on the instrument from previous tests disappear when a new test begins.
  • Page 53 RUNNING A TEST Figure 39 Edit test screen To provide a name for the test,press the Enter button with Name highlighted and then use the arrow keys to create the name. When finished, press the Save button. Enter initial moisture content if known (optional) by pressing the Enter button with Initial MC highlighted and use the up and down arrow to enter the correct moisture.
  • Page 54 AQUALAB VSA Figure 41 Edit stages DDI method 10. Select New and press the Enter button. A screen with several parameters will appear. Figure 42 Edit stages DDI method 11. Select the isotherm method as either DDI or DVS. DDI creates a dynamic isotherm and DVS makes a static or equilibrium isotherm. The other choices adjust according to your selected method.
  • Page 55 . The resolution for DDI determines the target a resolution. Setting a higher step value makes the test faster, but decreases the a resolution. METER recommends a DDI step of 0.01 a Figure 43 Edit stages DVS method To choose the air flow rate, highlight “Flow,” press the Enter button, and then cycle to the desired value using the up and down arrows.
  • Page 56 AQUALAB VSA For the DVS Method To choose the starting a , highlight “Start,” press the Enter button. Figure 44 Edit stages DVS method Cycle to the desired value using the up and down arrows. Choose any value between 0.03 and 0.95 a including “current.”...
  • Page 57 METER recommends beginning with two events at 0.01%/hr. If you turn the trigger off, the VSA holds the sample at each step for the time in the timeout setting. After adjusting all settings, press the Save button to save the settings and return to the Stage Setup screen.

  • Page 58: Using Ddi To Investigate Glass Transition

    AQUALAB VSA 15. To choose to have the isotherm loop, highlight “Loop” and press the Enter button to toggle between on and off. Turning loop on causes the isotherm to automatically return to the start a (with the same settings) once the final a has been achieved.

  • Page 59: Editing A Running Isotherm Test

    RUNNING A TEST 7.6 EDITING A RUNNING ISOTHERM TEST Users can edit a test that is already running by adding additional stages to a running test (inserted after the current running stage) at any time using the edit test function. This can be done using either the instrument interface or the software.

  • Page 60: Running A Water Activity Test

    Note: The Water activity test cannot be done when the isotherm test is running You can also use the AQUALAB VSA as a water activity meter. For best results and temperature control, METER recommends using a clean stainless steel cup for water activity testing and that you remove the weighing pan and place the cup directly on air cylinder when testing for water activity.

  • Page 61: Sample Preparation

    Completely cover the bottom of the cup, if possible, to provide enough sample to get an accurate reading. The AQUALAB VSA is able to accurately measure a sample that does not (or cannot) cover the bottom of the cup. For example, raisins only need to be placed in the cup and do not need to be flattened to cover the bottom.

  • Page 62: Coated And Dried Samples

    AQUALAB VSA Wipe any excess sample material from the rim and outside of the sample cup with a clean KIMWIPES tissue prior to loading the sample into the instrument. Material left on the rim or the outside of the cup can contaminate the chamber and can be transferred to subsequent samples.

  • Page 63: Volatile Samples

    SAMPLE PREPARATION METER recommends running the test as a DVS rather than DDI to ensure equilibrium is reached. DDI tests on these sample types do not reach full equilibrium and can show increased hysteresis. Sampling techniques are especially important for these sample types. The more surface area to volume the better the test runs.

  • Page 64: Service

    Customer Support. NOTE: Read through the troubleshooting portions thoroughly before contacting METER for assistance. If the AQUALAB VSA instrument was purchased from an international distributors, please contact them for local service and support.
  • Page 65 The mirror may be dirty. Clean the mirror and chamber (Section 5.2) and measure the sample again. Dew point sensor failure The cooler is damaged and needs to be serviced by METER. Refer to error message Section 9.3 for detailed instructions.
  • Page 66 If Auto Restart is on, the test automatically resumes after a device reset. If Auto Restart is turned off, then the test stops running Power was reset message following a device reset. To prevent device resets, METER strongly recommends connecting the VSA to an Uninterruptible Power Supply (UPS).
  • Page 67 SERVICE Table 6 Troubleshooting the AQUALAB VSA (continued) Problem Possible Solutions Fill the water tank (Section 4). Secure the water chamber plug. Weight is decreasing during Verify the pump is working. absorption Check if sample material is undergoing a phase change.
  • Page 68 AQUALAB VSA Table 6 Troubleshooting the AQUALAB VSA (continued) Problem Possible Solutions Press the check button to retry balance communication. Balance Communication Cycle the power on the instrument. Failure error message Contact Customer Support. If, after cleaning the instrument and following troubleshooting...

  • Page 69: Customer Support

    SERVICE • Desiccant: The desiccant humidity value indicates the effectiveness of the desiccant tubes. Initially when the diagnostic screen is turned on, the pump supplies flow through the active desiccant tube to help verify that it can desiccate properly. After 30 seconds of pumping, the desiccant humidity reading should be 5% or less.

  • Page 70: Repair

    METER has loaner instruments available for a fee while the AQUALAB VSA is being serviced. All AQUALAB VSA units returning to METER for servicing must be accompanied with a Return Merchandise Authorization (RMA) number. Prior to shipping the instrument, contact Customer Support to obtain an RMA number.
  • Page 71 SERVICE APPENDIX A. NONCONDENSING CONDITIONS FOR VSA TESTING This table shows the maximum advisable ambient humidity levels for the ambient room and test temperatures. Staying within these limits prevents condensation in and on the VSA. Operating in humidity and temperature conditions beyond these limits voids the VSA warranty and can damage the instrument.

  • Page 72: Index

    INDEX INDEX accuracy 4 phone number 64 annual calibration service 37, 38 read time 4, 56, 57 beep 6 repair 65–66 RMA number 65 calibration 38 restore 43–44 sample composition Certificate of Calibration 1, 65 coated 57 charcoal 36 dried 57 cleaning 31–34 multicomponent 56 cleaning kit 1, 34–35...
  • Page 73 14512-01 2.2022 METER Group, Inc. USA 2365 NE Hopkins Court Pullman, WA 99163 T: +1.509.332.2756 F: +1.509.332.5158 E: info@metergroup.com W: metergroup.com METER Group AG Mettlacher Straße 8, 81379 München T: +49 89 1266520 F: +49 89 12665220 E: info.europe@metergroup.com W: metergroup.de...

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