Decagon AquaLab User Manual
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Decagon AquaLab User Manual

Vapor sorption analyzer
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Vapor Sorption
Analyzer
User's Manual
Version 2

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Summary of Contents for Decagon AquaLab

  • Page 1 Vapor Sorption Analyzer User‘s Manual Version 2...

  • Page 2: Table Of Contents

    Table of Contents 1. Introduction ..............1 About this Manual ............... 1 Warranty ................1 Customer Support ............... 2 Seller’s Liability ..............3 2. About the VSA ............... 4 Moisture Sorption Isotherms ..........4 Measurement Method ............5 Specifications ..............7 3.
  • Page 3 7. Verification of Calibration ..........54 Water Activity Verification ..........54 Verification Standards ............55 When to Verify for Linear Offset .........56 8. Running a Test ............. 65 Becoming Familiar with Stages ..........65 Running a Moisture Sorption Isotherm Test .......65 For DDI method ................69 For DVS method ................

  • Page 5: Introduction

    The VSA has a one year warranty on parts and labor. Your warranty is automatically validated upon receipt of the instrument. Decagon will contact you within the first 90 days of your purchase to see how the VSA is working for you.

  • Page 6: Customer Support

    AquaLab Vapor Sorption Analyzer 1. Introduction Customer Support If you ever need assistance with your VSA, or if you just have questions or feedback, there are several ways to contact us. Customer service representatives are available to speak with you Monday thru Friday, between 7am and 5pm Pacific time.

  • Page 7: Seller's Liability

    AquaLab Vapor Sorption Analyzer 1. Introduction Seller’s Liability Seller warrants new equipment of its own manufacture against defective workmanship and materials for a period of one year from date of receipt of equipment. The results of ordinary wear and tear, neglect, misuse, accident and excessive deterioration due to corrosion from any cause are not to be considered a defect.

  • Page 8: About The Vsa

    AquaLab Vapor Sorption Analyzer 2. 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. Moisture Sorption Isotherms The relationship between water activity (a...

  • Page 9: Measurement Method

    AquaLab Vapor Sorption Analyzer 2. About the VSA 8. Determine the equilibrium water activity of a mixture of dry ingredients. 9. Determine the degree of crystallinity of powders. 10. Determine the level of amorphous material in a product. 11. Determine critical water activities for phase transitions.
  • Page 10 AquaLab Vapor Sorption Analyzer 2. About the VSA determined using Decagon‘s patented chilled-mirror dewpoint sensor. Drying of the sample is imposed by flowing dry air from a desiccant tube across the sample. Wetting of the sample is imposed by saturating the air with water before it enters the chamber and flows across the sample.

  • Page 11: Specifications

    AquaLab Vapor Sorption Analyzer 2. About the VSA reservoir, and desiccant supply. Setup is as simple as plugging the instrument in, installing the desiccant tubes, and filling the water reservoir. Test parameters can be set using an onboard interface or using a connected computer and VSA software package.

  • Page 12: Theory

    AquaLab Vapor Sorption Analyzer 3. 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).

  • Page 13: Moisture Sorption Isotherm Methods

    AquaLab Vapor Sorption Analyzer 3. Theory often proves more valuable than placing them in a common classification. Icing Creme Filling Cake Wood Pulp Granola Bar Milk Powder Water Activity Figure 1. Moisture adsorption isotherms for icing (♦) , crème filling (■), cake (▲), wood pulp (♦), granola bar (*), and milk powder...
  • Page 14 AquaLab Vapor Sorption Analyzer 3. Theory take weeks. Additional challenges with this manual method include difficulty tracking the weight of the samples, removing the samples for weighing exposes them to ambient humidity, and at high humidities, there is the possibility of mold growth. Deca- gon‘s VSA Isotherm Generator uses the DVS method described...
  • Page 15 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.
  • Page 16 AquaLab Vapor Sorption Analyzer 3. Theory Hysteresis Figure 2 shows two isotherms, one obtained by wetting a sample from complete dryness and the other obtained by drying a sample from saturation. The arrows show the direction of the process. The water content at each water activity is higher during desorption (drying from high water content) than adsorption (wetting from low water content).
  • Page 17 AquaLab Vapor Sorption Analyzer 3. Theory 14.00 12.00 10.00 8.00 6.00 4.00 2.00 0.00 Water Activity Figure 3. Scanning adsorption curves resulting from drying to different water activities. 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 18 AquaLab Vapor Sorption Analyzer 3. Theory changes of non-porous solids, structural changes within a solid matrix, and supersaturation of some solutes during desorption. Depending on the composition of the sample, these theories explain why the water content of a desorption process is greater than that for a wetting process.
  • Page 19 AquaLab Vapor Sorption Analyzer 3. Theory Non-Equilibrium If diffusion of water into (adsorption) or out of (desorption) a material is slow and sufficient time is not allowed for complete diffusion, there will be a large amount of apparent hysteresis that could be reduced by allowing sample equilibration.
  • Page 20 AquaLab Vapor Sorption Analyzer 3. Theory desorption curves in the initial isotherm is not true hysteresis since the sample matrix has experienced a physical change. Differences between sorption curves in the subsequent isotherms represent true hysteresis. Water Activity Figure 4. Moisture sorption isotherms for spray-dried milk powder showing a change in hysteresis due to a phase change at 0.43 a...
  • Page 21 AquaLab Vapor Sorption Analyzer 3. Theory shows how a product adsorbs and desorbs water from its current or typical condition. To create a working isotherm, the product is processed as usual, and then a scanning curve is created by wetting one sample from that point and drying a different sample from that same point.
  • Page 22 AquaLab Vapor Sorption Analyzer 3. Theory Figure 5. A working isotherm () superimposed over a full isotherm (■) for wood pulp. There is a transition from the native starting point (0.60 a ) on the working isotherm in both adsorption and desorption until the curves meet the bounding adsorption and desorption curves of the full isotherm at which point the working isotherm follows the full isotherm.
  • Page 23 AquaLab Vapor Sorption Analyzer 3. Theory Where m is the moisture in g/100 solids or g/g solids at water activity a and m is the monolayer value in the same units. The      constant c is calculated by:...
  • Page 24 AquaLab Vapor Sorption Analyzer 3. Theory An additional function of the isotherm is moisture content prediction. Although water activity is a much better predictor of safety and quality than moisture content, there are times when it is necessary to know both water activity and moisture content as well as the relationship between the two parameters for a given product.
  • Page 25 AquaLab Vapor Sorption Analyzer 3. Theory Finally, sorption isotherms are valuable for shelf life prediction. A product‘s isotherm can be used to determine package requirements depending on the products sensitivity to moisture. It can also be used to determine the monolayer moisture content, which represents a products most stable state.

  • Page 26: Getting Started

     USB Interface Cable  2 Stainless Steel Sample Cups  2 Refillable Desiccant Tubes  1 Decagon Cleaning Kit  1 Water Bottle  3 Vials each of the following verification solution: 0.920 a 2.33 molal NaCl 0.760 a 6.0 molal NaCl...

  • Page 27: Instrument Setup

    2. Use AquaLab VSA where environmental temperature and humidity remain stable. 3. Plug in AquaLab VSA and turn on the power (switch in back). For best results, let the instrument warm-up for 2 hours before use. Lower plate...
  • Page 28 Vapor Sorption Analyzer 4. Getting Started 4. Install the 2 desiccant tubes in the front of the instrument.  Desiccant tubes are installed as shown in Figure 7: Desiccant installation. Before insertion make sure that the desiccant tube lid is firmly sealed onto the desiccant tube, remove black vinyl covers from air fittings.
  • Page 29 AquaLab Vapor Sorption Analyzer 4. Getting Started 5. Install the air cylinder and weighing pan. With the lid open, inset the air cylinder and weighing pan into the testing block as shown in Figure 8. These parts remain in the instrument continually and are only removed for maintenance.
  • Page 30 VSA is probably too unstable for accurate weight readings during a test and will need to be made more rigid or another location found for this equipment. Contact your AquaLab distributor if the scale readings are unstable after placing the unit on a stable structure.
  • Page 31 AquaLab Vapor Sorption Analyzer 4. Getting Started Water fill plug Upper horizontal drilled hole Water tank fill extension Water tank drain plug Fan filter Figure 9: Tank fill extension 8. Figure 9 also shows the location of the fan filter that will need to be removed from time to time when dust builds up on it.

  • Page 32: User Interface And Menus

    5. User Interface and Menus 5. User Interface and Menus The AquaLab VSA is a stand-alone instrument that uses arrows and 3 buttons to navigate menus and begin tests. At the top of the display screen there are 4 tabs: Isotherm, Measurement, Configuration, and Data.

  • Page 33: Measurement Tab

    AquaLab Vapor Sorption Analyzer 5. User Interface and Menus 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 will change the display to a temperature equilibration screen shown below.
  • Page 34 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus options. The enter button will allow you to change the highlighted setting.
  • Page 35 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus Calibration: Pressing the Enter button when Calibration is highlighted opens the calibration menu where either a water activity or weight adjustment can be made. For more details on weight and water activity calibration procedures refer to the chapter on Verification of Calibration.
  • Page 36 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus with certain volatiles in high enough concentrations may give inaccurate water activity values. This is because the volatiles condense on the mirror during the reading process, but do not evaporate from the mirror as water does. As a result, the reading on samples with volatiles will not be accurate.
  • Page 37 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus basis parameter allows the reporting of moisture content in two different ways: Percent moisture on a wet basis (%wb, g/100g total) initial weight dry weight grams water   %Moisture grams...
  • Page 38 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus Time: Pressing Enter when the Time option is 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.
  • Page 39 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus Temperature: This setting is the temperature that the instrument maintains during water activity measurements. It also is the temperature that the instrument will return to after a test is complete. The default temperature is 25°C. Press the enter button to change the temperature setting.
  • Page 40 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus Regional Formatting: Allows you to configure how the VSA will display information. You may choose the temperature scale (Celsius vs Fahrenheit), the date display (mm/dd/yy vs. dd/mm/yy), the hour format (12 vs 24 hour) and the language.
  • Page 41 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus User Setup: Users can be added, edited or deleted from this screen. To add a user, press the Enter button when the ―New‖ is highlighted. To edit or delete a user, choose the target user and press enter.
  • Page 42 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus Auto Restart: Auto restart enabled the instrument to automatically resume the currently running test if there is a power failure of any kind. Press enter to toggle auto restart between on and off.
  • Page 43 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus 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 44 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus Diagnostics: The diagnostics screen provides you with detailed information about all the sensors in the instrument. Refer to the Troubleshooting section for details on what kind of values you should expect for each sensor.
  • Page 45 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus The weight icon on the bottom allows you to zero the balance so that you can take weight readings via the diagnostic screen. The weight calibration value is the current calibration applied to balance readings.
  • Page 46 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus right, it switched to the right desiccant tube (#2). Any time the desiccant tube button is pressed the pump is turned on and dry air is blown into the chamber so that desiccating capacity of the tubes can be monitored.

  • Page 47: Data Tab

    AquaLab Vapor Sorption Analyzer 5. User Interface and Menus Data Tab This tab allows you to view detailed information about the test stored in memory. You can view data as a list, view detailed data point information, and graph all or individual stages. You can also delete the data in memory.
  • Page 48 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus each data record. See Chapter 11: Computer Interface for information about downloading test data to a computer. Graph Screen: This selection shows the graph of the selected data from the previous screen. You can change the y-axis units by pressing the left or right arrows or change the x-axis units by pressing the up or down arrows.
  • Page 49 AquaLab Vapor Sorption Analyzer 5. User Interface and Menus Summary Screen: This selection will allow you to view your stored measurements. The up/down arrows will 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.

  • Page 50: Cleaning And Maintenance

    AquaLab Vapor Sorption Analyzer 6. Cleaning and Maintenance 6. Cleaning and Maintenance Desiccant cartridge desiccant replacement. Removal of the desiccant material 1. Orient the desiccant cartridge or tube (Figure 10) so the lid or cap is up. 2. Remove the main lid.
  • Page 51 AquaLab Vapor Sorption Analyzer 6. Cleaning and Maintenance Loading the desiccant into the desiccant cartridge. 1. Orient the desiccant tube so the opening is upward. 2. Hold the tubing to the side of the cartridge and looped over the edge of the cartridge.

  • Page 52: Cleaning The Testing Chamber

    AquaLab Vapor Sorption Analyzer 6. Cleaning and Maintenance b. Hold one finger over the output fitting c. Pressurize the desiccant tube using the pressure bottle as shown in Figure 13. (Note: The bottle just needs squeezed with air in it.
  • Page 53 A thin plastic rod or other non-metal implement • Distilled Water • Isopropyl Alcohol (IPA) or Decagon Cleaning Solution • Kimwipes® You may also purchase the VSA Cleaning Kit which comes with all the above materials except the Isopropyl Alcohol and Distilled Water.
  • Page 54 Accessing the Sample Chamber Turn the power off on your AquaLab VSA. If latched, move the lever over to the open position. Lift the chamber cover to expose the VSA sample chamber and sensors. The sample chamber...
  • Page 55 Wrap a NEW Kimwipe around the end of the thin plastic rod (spatula) and moisten it with isopropyl alcohol or Decagon Cleaning Solution. Note: Do NOT dip a used Kimwipe into your container of IPA or cleaning solution (the IPA or cleaning solution will become contaminated).
  • Page 56 AquaLab Vapor Sorption Analyzer 6. Cleaning and Maintenance b. WASH—Swipe the moistened Kimwipe across the mirror once. (A single swipe is usually sufficient to remove contaminants.) c. RINSE—Repeat steps a-b using new Kimwipes moistened with distilled water instead of cleaning solution.
  • Page 57 AquaLab Vapor Sorption Analyzer 6. Cleaning and Maintenance 4. Additional Drying Time a. Visually inspect the sample chamber and sensors for contaminants, including moisture. If necessary, repeat the cleaning process using new Kimwipes. b. Let stand for about 5 minutes to ensure the sample...

  • Page 58: Verification Of Calibration

    Water Activity Verification AquaLab VSA uses both a capacitance relative humidity sensor and a chilled-mirror dew point technique to determine water activity. If volatiles is set to ―yes‖ as described in Chapter 5, water activity verification will be performed on the capacitance sensor only, but if volatiles is set to ―no‖, the dewpoint sensor will...

  • Page 59: Verification Standards

    Decagon. Using verification standards to verify accuracy can greatly reduce preparation errors. For these reasons, we recommend using standards available through Decagon for the most accurate verification of your VSA‘s performance. Performance Verification Standards come in six water activity levels: 1.000, 0.984, 0.920, 0.760, 0.500, and 0.250 a...

  • Page 60: When To Verify For Linear Offset

    7. Verification of Calibration Although distilled water is available as a verification standard. Decagon does not recommend its use with the AquaLab VSA. To use a verification standard, remove the twist top and pour the contents into one of the stainless steel sample cups. Information about the standard‘s value and molality can be found printed on...
  • Page 61 ± 0.005 a of the given value for the verification standard. See Appendix A for the correct water activity value of Decagon‘s standards at temperatures other than 25°C. 7. If your VSA is reading within ±0.005 a of the verification standard, choose a 0.76 a...
  • Page 62 AquaLab Vapor Sorption Analyzer 7. Verification of Calibration Figure 14. This flowchart is a graphical representation of the directions given above for checking for linear offset. Adjust for Linear Offset for Water Activity 1. Once you are certain a linear offset has occurred, toggle to the Configuration tab by pressing the Menu icon button.
  • Page 63 AquaLab Vapor Sorption Analyzer 7. Verification of Calibration 2. To offset for water activity, highlight water activity and press and the following screen will appear. 3. Highlight start and press . Follow the wizard on screen commands. 4. Empty the whole vial of solution into a sample cup. We recommend using the 6.0 NaCl (0.76 a...
  • Page 64 If you still have incorrect verification standard readings after cleaning the chamber and adjusting for linear off set, contact AquaLab by email at support@aqualab.com or by phone at 509-332-5601 for further instructions. If you purchased your AquaLab instrument from one of our international distributors, please contact them for local service and support.
  • Page 65 AquaLab Vapor Sorption Analyzer 7. Verification of Calibration Verifying Weight Measurement The VSA uses a magnetic force balance to gravimetrically track the weight of the sample during the isotherm test. The performance of this balance is verified against a NIST traceable 2 gram standard weight.
  • Page 66 AquaLab Vapor Sorption Analyzer 7. Verification of Calibration 5. Open the lid and carefully place the 2 gram standard on the balance using glove and tweezers. 6. Close the lid and verify that the weight readings are within +/- 0.1 mg of 2000mg. If the weight reading is not correct, a balance adjustment may be needed.
  • Page 67 To cancel and return to the main menu, press no changes will be made. If you continue to have problems with weight readings, contact AquaLab by email at support@aqualab.com or by phone at 509-332-5601 for further instructions. If you purchased your AquaLab instrument from one of our international distributors, please contact them for local service and support.
  • Page 68 AquaLab Vapor Sorption Analyzer 7. Verification of Calibration 2. Select water activity or weight, depending on which defaults you want to restore and press 3. Scroll down to Defaults and press the icon button to access the Restore Factory Defaults routine. To cancel and return to the main menu, press the Cancel icon button.

  • Page 69: Running A Test

    8. Running a Test 8. Running a Test 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 1 sample.
  • Page 70 AquaLab Vapor Sorption Analyzer 8. Running a Test the VSA Downloader software (see Chapter 9 for more information). 1. Before starting a test, set the Volatiles: Yes/No option in the configuration menu. If your sample has volatiles, select ―Yes‖ otherwise select ―No‖.
  • Page 71 AquaLab Vapor Sorption Analyzer 8. Running a Test 5. The Edit Test screen will now appear. To provide a name for the test, press with Name highlighted and then use the arrow keys to create the name. When finished, press (The name of a previous test will appear by default.)
  • Page 72 AquaLab Vapor Sorption Analyzer 8. Running a Test 7. Setup each stage of the isotherm test. A stage is used to adjust the isotherm settings for an individual sample (up to 20 stages). Each stage is setup with the isotherm method (DDI or DVS) and the settings for that portion of the isotherm.

  • Page 73: For Ddi Method

    AquaLab Vapor Sorption Analyzer 8. Running a Test test has been run, the stages for that test will be listed by default. These stages can be used as is or updated with new settings. If you need to delete or edit a stage, go to the specific stage and press and then select Edit or Delete.
  • Page 74 AquaLab Vapor Sorption Analyzer 8. Running a Test Selecting a final a that is lower than the starting a will result in desorption, while selecting a final a higher than the starting a will result in adsorption. Press when finished.
  • Page 75 AquaLab Vapor Sorption Analyzer 8. Running a Test 6. To choose to include a timeout setting, press with ―Timeout‖ highlighted, and then cycle to the desired value using the up and down arrows. Any value between 5.0 min to 30 days can be selected. The timeout determines the...

  • Page 76: For Dvs Method

    AquaLab Vapor Sorption Analyzer 8. Running a Test For DVS method with ―Start‖ highlighted, 1. To choose the starting a , press and then cycle to the desired value using the up and down arrows. Any value between 0.03 and 0.95 a can be chosen including ―current‖.
  • Page 77 AquaLab Vapor Sorption Analyzer 8. Running a Test To choose the trigger %dm/dt value that will indicate equilibration, press enter with ―Trigger‖ highlighted and a new window will open. Cycle to the desired trigger value using the up and down arrows. The trigger can be shut off or be any value between 0.001-1%/hr.
  • Page 78 AquaLab Vapor Sorption Analyzer 8. Running a Test 5. To choose to include a timeout setting, press with ―Timeout‖ highlighted and then cycle to the desired value using the up and down arrows. Any value between 5.0 min to 30 days can be selected. The timeout determines the...

  • Page 79: Using Ddi To Investigate Glass Transition

    AquaLab Vapor Sorption Analyzer 8. Running a Test 9. Follow the message on the screen to place an empty stainless steel cup in the chamber and seal it. Press tare the cup. 10. Follow the message on the screen to place the sample in the cup and press to weight the sample.

  • Page 80: Editing A Running Isotherm Test

    AquaLab Vapor Sorption Analyzer 8. Running a Test activity of the sample. Upon completion of the isotherm, the data is downloaded and the test saved using a name that will identify the sample name and the sorption direction. 3. Desorption Curve: A second sub-sample is analyzed for desorption from its current state.
  • Page 81 AquaLab Vapor Sorption Analyzer 8. Running a Test 2. Press the icon to edit the selected test. The following screen will appear 3. The current running stage (spinner icon) and completed stages (lock icons) cannot be edited. To add additional stages, select new and press .

  • Page 82: Running A Water Activity Test

    Running a Water Activity Test (Can’t be done when isotherm test is running) The AquaLab VSA can also be used as a water activity meter. For best results and temperature control, we recommend you use 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 83: Vsa Downloader Software

    AquaLab Vapor Sorption Analyzer 9. VSA Downloader Software 9. VSA Downloader Software While the AquaLab VSA can operate as a stand-alone instrument, a computer must be attached to download test results. The VSA Downloader software makes it easy to download moisture sorption isotherm measurements from your VSA, view the data in table or chart form, export for use in other programs, and easily setup a new test with multiple stages.

  • Page 84: Download And Export

    AquaLab Vapor Sorption Analyzer 9. VSA Downloader Software Modify a Currently Running Test Note: You can only modify stages that have not yet begun. If you wish to modify the current running stage, simply create a new stage and adjust your stage behavior from the current reading of the VSA.

  • Page 85: Troubleshooting

    Decagon for help (see Customer Support in Chapter 1). Here is a list of some problems that may occur. NOTE: If you purchased your AquaLab VSA instrument from one of our international distributors, please contact them for local service and support.
  • Page 86 AquaLab Vapor Sorption Analyzer 10. Troubleshooting Troubleshooting Quick Guide Continued Screen displays "Contaminated Mirror" ...... Problem #9 Screen displays "Firmware is corrupted"....Problem #10 Screen displays "Missing bootstrap loader" ....Problem #11 Screen displays ―Annual calibration due‖....Problem #12 Screen displays ―No equilibration points available!‖...
  • Page 87 AquaLab Vapor Sorption Analyzer 10. Troubleshooting Troubleshooting Quick Guide Continued Scale Readings are not stable or balance cannot be started ............. Problem #25 Scale calibration is failing ......... Problem #26 Desiccant cartridges are hard to install ..... Problem #27 Poor temperature control on the system ....Problem #28 Diagnostic Screen ............
  • Page 88 If you have further questions regarding the measurement of volatiles contact Decagon. 5) A fan blade in the block chamber may be broken or bent. If even salt standards take a long time to read, and the...
  • Page 89 10. Troubleshooting chamber fan blade. This is especially likely if you have just cleaned the chamber. If you suspect this may have happened, contact Decagon for details on replacement. 3. PROBLEM: Water activity readings on verification standards are too high/low and a linear offset adjustment cannot be made any higher/lower.
  • Page 90 AquaLab Vapor Sorption Analyzer 10. Troubleshooting samples will take a very long time to measure for the same reason. To avoid this problem, make sure to only measure samples that are at the same temperature as the instrument. 5. PROBLEM:...
  • Page 91 6. PROBLEM:Message on screen displaying dew point sensor failure. SOLUTION: The Cooler is damaged and will need to be serviced by Decagon. See Chapter 12 for detailed instructions. 7. PROBLEM Verification is not correct. SOLUTIONS: 1) The sample chamber and mirror need to be cleaned. See Chapter 6 for detailed cleaning instructions.
  • Page 92 The crystal that runs the firmware is having trouble starting. Occasionally, cycling the power will solve the problem. If this message continues to appear, the instrument will need to be serviced by Decagon. See Chapter 13 for detailed instructions. 9. PROBLEM: Message on the screen displays the following:...
  • Page 93 The mirror used for dew point measurements requires cleaning. Follow the instructions outlined in Chapter 6: Cleaning and Maintenance before trying to run your sample again. If this message continues to appear, contact your Decagon for further options. 10. PROBLEM: Message on the screen displays the following:...
  • Page 94 SOLUTION: This message indicates that it‘s been at least a year since the instrument has been calibrated and serviced by Decagon or your local distributor. It is recommended that you return your instrument so that we can help you ensure you are getting the most accurate readings possible from your VSA.
  • Page 95 AquaLab Vapor Sorption Analyzer 10. Troubleshooting 13. PROBLEM: Message on the screen displays the following: SOLUTION: When graphing a test, this message indicates that there are no data points in which the weight has stabilized. The time it takes for an equilibration point to appear depends on the sample phase changes and stage trigger/ timeout specifications.
  • Page 96 6) Water chamber plug is not properly installed or missing. 7) Pump system is failing If you continue to receive a message after the above items have been checked, contact Decagon for further options. 16. PROBLEM: Message on the screen displays the following:...

  • Page 97: Screen Indicates A Scale Failure

    This may be caused by a dirty chamber, a faulty or damaged air cylinder, a misaligned scale shaft or a pump assembly problem. Clean the chamber including the air cylinder, the weighing pan, and the space beneath the air cylinder. If you continue to have problems, contact Decagon.

  • Page 98: Can't Communicate With The Vsa

     The test must have a name.  The test must contain at least one stage. If you continue to receive this error, contact Decagon. 20. PROBLEM: Can‘t communicate with the VSA. SOLUTIONS: 1) USB cable is not plugged in.

  • Page 99: Weight Is Decreasing During Adsorption

    AquaLab Vapor Sorption Analyzer 10. Troubleshooting 21. PROBLEM: Weight is decreasing during absorption. SOLUTIONS: 1) Water tank has run dry. 2) Plug on fill tank is loose. 3) Pump is not working. 4) Material is undergoing a phase change. 5) Scale needs to be checked for calibration.
  • Page 100 AquaLab Vapor Sorption Analyzer 10. Troubleshooting 24. PROBLEM: Isotherm test is taking an unusually long time to complete, even at high flow rates. SOLUTIONS: 1) Sample has very slow sorption properties. 2) Water has run out – fill. 3) Desiccant is used up – replace.

  • Page 101: Diagnostic Screen

    AquaLab Vapor Sorption Analyzer 10. Troubleshooting 27. PROBLEM: Desiccant cartridges hard to install. SOLUTIONS: Dampen the o-rings on the desiccant cartridge using water before installing 28. PROBLEM: Poor temperature control on the system. SOLUTIONS: 1) Clean the filters on the enclosure fans.
  • Page 102 AquaLab Vapor Sorption Analyzer 10. Troubleshooting This screen shows typical values for the temperature sensors on the instrument. Press up and down to scroll between the different pages. Lid, base and sample temperatures may fluctuate but should not change more than 0.03 degrees. Typical ranges for the lid, base and sample temperatures are between 24.5 and...
  • Page 103 AquaLab Vapor Sorption Analyzer 10. Troubleshooting Latch: To determine if the latch is functioning properly, open and close the latch while monitoring the latch status on the screen. If the screen doesn‘t update the latch status when you open and close the latch, the latch magnet may need to be re- seated (with the correct polarity) or the Hall Effect sensor needs to be realigned with the magnet.
  • Page 104 AquaLab Vapor Sorption Analyzer 10. Troubleshooting Weight Cal: The weight calibration saved a scalar into memory that‘s applied to all subsequent weight readings. A scalar of 1 means that the weight hasn‘t been changed from it‘s default factory calibration. If the scalar strays too far from 1, you may need to reverify the balance and also recertify the weight standard.
  • Page 105 0.920 35.0 1.000 0.984 0.760 0.508 0.261 0.921 40.0 1.000 0.984 0.760 0.512 0.266 0.920 50.0 1.000 0.984 0.759 0.517 0.275 60.0 1.000 0.984 0.894 0.740 0.505 0.279 The Aqualab Vapor Sorption Analyzer will measure these standards to ±0.005 a...

  • Page 106: Index

    AquaLab Vapor Sorption Analyzer Index Index AquaLab VSA Information, 4 Equilibrium isotherms, 6 External gas, 6, 38 Balance magnetic force, 61 Flow rate, 70, 96 Calibration, 31 Glass transition, 5, 11, 21 verification, 54 Cleaning block and sensors, 50 Humidity operating range, 7...
  • Page 107 AquaLab Vapor Sorption Analyzer Index control range, 7 operating range, 7 Matrix changes, 15 Test wizard, 66 Measurement tab, 29 Theory, 8 Moisture Content Trigger, 73 basis, 32 Troubleshooting, 81 Moisture Sorption Isotherm moisture sorption, 4 test, 65 User Interface, 28...

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