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Operator`s Manual - manuals.decagon.com

1. Figure 4 Spray Dried Milk Moisture Sorption Isotherms Working Isotherms Full boundary isotherms give information about the physical charac teristics of a product show hysteresis and are important in estab lishing critical control points but in many cases a working isotherm proves very useful A working isotherm shows how a product ad sorbs and desorbs water from its current or typical condition To create a working isotherm process the product as usual and then create a scanning curve by wetting one sample from that point and drying a different sample from that same point Figure 5 shows a working isotherm blue diamond superimposed over a full isotherm red square for wood pulp There is a transition from the native starting point 0 60 aw 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 The scanning curve the product initially follows depends on whether the product was previously wetted or dried to its current state If you wet a product to a certain water activity and then dry it back down there is an initial transition period as the product moves from the adsorption curve to the desorption curve The same is true for a 15 3 THEORY AquaLab VSA product that you previously dried and then wetted up There is an initial transition period as the product mo
2. 87 11 TROUBLESHOOTING AquaLab VSA Errar There was a critical error Starting the test See Manual for options SOLUTION Verify that the following three items before starting a test 1 The sample weight is at least 50 milligrams 2 The test must have a name 3 The test must contain at least one stage If you continue to receive this error contact Decagon 20 PROBLEM Cannot communicate with the VSA SOLUTIONS 1 USB cable not plugged in to power 2 Wrong com port selected 3 Restart VSA 4 Restart communication software 21 PROBLEM Weight is decreasing during absorption SOLUTIONS Water tank has run dry Plug on water fill tank loose Pump is not working Material is undergoing a phase change Scale needs to be checked for calibration oR WN 88 AquaLab VSA 11 TROUBLESHOOTING 22 PROBLEM Weight is increasing during desorption SOLUTIONS 1 Desiccant cartridge has been used up 2 Pump is not working 3 Desiccant tube tubes leaking 4 Scale needs to be checked for calibration 23 PROBLEM Isotherm test has stopped prematurely SOLUTIONS 1 Download the test with the Moisture Analysis Toolkit 2 Navigate to the Table view 3 Scroll down to the last data record in the list 4 Look in the special condition column to see what caused the test to stop prematurely 5 Refer to the troubleshooting section that references the special condition indic
3. Before starting a test it is important to verify that the VSA is per forming correctly using Decagon s Verification Standards Please refer to Section 7 for instructions on how to verify your VSA and adjust the calibrations if necessary Tests can also be setup using a Wizard interface in the Moisture Analysis Toolkit software see Sec tion 9 for more information Note Before starting a test refer to Appendix B to verify you are running under non condensing conditions as this could void your warranty 60 AquaLab VSA 8 RUNNING A TEST 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 2 On the Main screen select the Test Wizard 3 The Warning screen appears to let the user know that any data points currently on the instrument from previous tests disappear when you begin a new test Select the double right arrow to continue Warning Any readings in memory will be erased when the new test is started EJ 4 A new message reminding the user to make sure the water chamber is full and there is still active blue desiccant in the desiccant tubes For instructions on filling the water chamber and replacing the desiccant refer to Section 4 and Section 6 respectively Press the double right arrow to continue or the double left arrow to go back Test Wizard Ensure the water chamber is full Check the blue d
4. 2 The temperature difference between the sample and the block chamber may be too great The sample needs to equilibrate to instrument temperature before a fast accurate reading can be made Refer to Section 8 79 11 TROUBLESHOOTING AquaLab VSA 3 Some products absorb or desorb moisture very slowly causing measurements to take longer than usual and nothing can be done to speed up the process Refer to Section 8 for further explanation 4 Your sample may contain volatiles Volatiles are known to cause unstable readings because they condense on the sur face of the chilled mirror and alter readings Please refer to the volatiles section in Section 8 for hints on reducing difficul ties with measuring samples with volatiles If you have fur ther 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 sample chamber is clean you may have a broken 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 SOLUTIONS 1 The thermopile in your chamber which measures sample tem perature may have become contaminated Refer to Section 6 for direction
5. Note If you purchased your AquaLab VSA instrument from one of our international distributors please contact them for local service and support 77 11 TROUBLESHOOTING AquaLab VSA Table 2 Troubleshooting Quick Guide If this problem occurs Refer to VSA does not turn on Problem 1 Readings are slow or inconsistent Problem 2 Ay readings on solutions are too high low to ad Problem 3 just Screen displays sample too hot Problem 4 Screen displays ay lt 0 0 Problem 5 Dew point sensor failure Problem 6 Verification is not correct Problem 7 Screen displays Crystal Failure Problem 8 Screen displays Contaminated Mirror Problem 9 Screen displays Firmware is corrupted Screen displays missing bootstrap loader Screen displays annual calibration due Screen displays no equilibration points available Screen displays desiccant tube is low Displays Low or High System Pressure Warning Screen displays Power was reset Screen indicates a scale failure overload or under load Screen displays Actuator failure Critical error starting a test Cannot communicate with the VSA Weight is decreasing during adsorption Weight is increasing during adsorption Isotherm test has stopped prematurely Isotherm test taking unusually long time to com plete Scale Readings are not stable or balance cannot be started Scale calibration is failing Desiccant ca
6. press the Check Mark To cancel and return to the main menu press the Cancel but ton After pressing the Check Mark the Calibration aw screen verifies that VSA has restored the factory calibration 57 7 VERIFICATION OF CALIBRATION AquaLab VSA Calibration a Factory calibration restored Similar screens appear if you are restoring the weight factory defaults but the screen says weight instead of water activity Select the Check Mark to return to the Configuration tab 7 4 Isotherm Standard Comparison If concerns arise about the accuracy of the moisture sorption curves the VSA produces it is possible to perform a moisture sorption stan dard comparison This can only be done using the Moisture Analysis Toolkit software and must be performed on Microcrystalline Cellu lose MCC We included a sample of MCC with your instrument or you can use your own lab grade MCC Contact AquaLab Support if you need additional MCC samples To run an isotherm standard test go to actions and select Run Standard Test in the software This initiates a Test Wizard to walk you through the steps to initiate a test The settings of this test are preset and the test takes four to five days to complete If the Moisture Analysis Toolkit software remains connected to the instrument throughout the duration of the standard test the soft ware prompts the user to save a pdf report of the test after which it graphs the newly created isotherm for
7. 38 AquaLab VSA 5 USER INTERFACE AND MENUS MCC DDI Dew Point 1 4 34PH BOY 4ra DOI 5H 570 5 ir DO 30 60 90 120 i50 Note For DVS isotherms if water activity is the x axis only equili brated data points appear on the chart To view all the data points the x axis must be in terms of the time elapsed 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 Data O O O o oo i an A Sy 24 93 C 4 7 min 1322 7 mg 09 01711 Dew Point 4 04PM i 1 17 The information shown is the water activity of the sample the tem perature the test time the user who ran the test if setup the date of the reading the sensor used the time of the reading and the se quence number of the stored reading Delete Selecting this option deletes all of the information currently stored 39 5 USER INTERFACE AND MENUS AquaLab VSA in the instrument Note You are not able to recover deleted data so make sure you have backed up your data to the computer using the Moisture Anal ysis Toolkit software package prior to deleting the data from the in strument 40 AquaLab VSA 6 CLEA
8. 99 C Sample 25 12 C Mirror 28 32 C G 2 Scroll down until you see weight on the screen Diagnostics RH 23TH 22783 A Weight 1565 6 mg Optical SOG ri y Latch as ar 3 Close the lid and seal by pressing the lever to read 4 Press the balance icon at the bottom to zero the balance 5 When placing the two gram weight on the balance handle care fully with tweezers and gloves to prevent changing the weight of the standard 6 Close the lid and verify that the weight readings are within 0 1 mg of 2000 mg If the weight reading is not correct your instrument may require a balance adjustment Adjusting for Weight Measurement Offset 1 To adjust the balance toggle to the Configuration tab by press ing the Menu icon Calibration is the first option highlighted 55 7 VERIFICATION OF CALIBRATION AquaLab VSA in the configuration tab Press the Enter button to bring up the Calibration screen Calibration Water Activity Weight x 2 To adjust the balance highlight weight press the Enter button and the Calibration Weight screen appears Calibration Weight Defaults x 3 Highlight start and press the Enter button Follow the wizard on screen commands 4 When asked to place the two gram weight on the balance han dle carefully with tweezers and gloves to prevent changing the weight of the standard 5 Carefully close the lid and move the lever to the read position
9. Conditions for VSA Testing Non Condensing Ambient Humidity Limit for Test Temperatures Below 25 C Ambient 15 C Test 17 C Test 20 C Test 23 C Test 25 C Test Temperature C Temperature Temperature Temperature Temperature Temperature 16 0 93 8 100 0 100 0 100 0 100 0 17 0 88 0 100 0 100 0 100 0 100 0 18 0 82 6 93 9 100 0 100 0 100 0 19 0 77 6 88 2 100 0 100 0 100 0 20 0 72 9 82 9 100 0 100 0 100 0 21 0 68 6 779 94 0 100 0 100 0 22 0 64 5 73 3 88 4 100 0 100 0 23 0 60 7 69 0 83 2 100 0 100 0 24 0 57 1 64 9 78 4 94 1 100 0 25 0 53 8 61 2 73 8 88 7 100 0 26 0 50 7 57 6 69 5 83 6 94 2 27 0 47 8 54 3 65 6 78 8 88 8 28 0 45 1 51 2 61 8 74 3 83 8 29 0 42 6 48 4 58 3 70 1 79 1 30 0 40 2 45 6 55 1 66 2 74 6 31 0 37 9 43 1 52 0 62 5 70 5 32 0 35 8 40 7 49 1 59 1 66 6 33 0 33 9 38 5 46 4 55 8 62 9 34 0 32 0 36 4 43 9 52 8 59 5 35 0 30 3 34 4 41 5 49 9 56 3 36 0 28 7 32 6 39 3 47 2 53 3 37 0 27 1 30 8 37 2 44 7 50 4 38 0 25 7 29 2 35 2 42 4 47 8 39 0 24 4 27 7 33 4 40 1 45 3 40 0 23 1 26 2 317 38 0 42 9 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 Please contact us if you have any questions or require any additional assistance 97 15 DECLARATION OF CONFORMITY AquaLab VSA 15 De
10. Diagnos tics screen and press the left arrow or Enter button 22 AquaLab VSA 4 GETTING STARTED Sample Cup Lid Only used for sample storage and must be removed during tests Sample cup Stainless steel cups are recommended Plastic cups absorb moisture over time Weighing Pan Air Cylinder Base Block Bore Figure 8 Sample Cup and Lower Block Assembly c a e Scroll down highlight Diagnostics and press the Enter button Scroll down to the screen that shows the weight Read ings should vary no more than 0 1 mg once the scale has stabilized Lightly tap the table with one finger If the readings vary more than 0 2 mg after tapping the table holding the VSA is probably too unstable for accurate weight read ings during a test You need to make the table more rigid or find another location for this equipment Contact your AquaLab distributor if the scale readings are unstable af ter placing the unit on a stable structure 7 Fill the water tank Remove the black plug on the clear plastic tank fill extension located on the back right of the VSA Fig ure 9 Fill the tank with United States Pharmacopeia USP purified water until full to top Reinstall the black plug once finished The black plug should be hand tightened only 8 Figure p shows the location of a filter that you must remove and blow out from time to time when dust builds up on it The housing around the filter is a
11. MCC along with a preloaded standard MCC curve to allow comparisons To create a permanent copy of the newly created MCC curve manually save it in the File Menu This pdf report contains a comparison of kinetic and moisture sorption isotherm curves as well as an error value for the compar ison of the newly created curve and the preloaded standard MCC curve We recommend a sample size of 1 g when running the MCC standard test An error value less than 0 12 would be acceptable If 58 AquaLab VSA 7 VERIFICATION OF CALIBRATION the error value is greater or equal to 0 12 contact AquaLab Support for 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 Instead save the completed MCC isotherm curve as a vsa file and then manually compare it to the preloaded standard MCC curve To do this select Standard Comparison from the ac tion menu in Moisture Analysis Toolkit software to open a file dialog box Navigate to and open the vsa file for the MCC isotherm curve The software outputs this curve at the conclusion of the standard test and you can compare these curves with any previously saved MCC standard isotherm curves Doing so initiates a comparison of this curve to the preloaded standard MCC curve and the system prompts you to save a pdf of the comparison report Customers can use the standard comparison feature anyt
12. TROUBLESHOOTING AquaLab VSA surements Optical A typical optical range is between 500 mV and 2900 mV 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 does not 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 Actuator The Act button toggles the actuator on and off lift ing the sample pan up and down to confirm the actuator functions properly Use this button to verify that the actuator works correctly and that it is not throwing off weight readings Occasionally contam inants or defects can cause the cylinder to stick and prevent accurate weight measurements The Act button is an easy way to verify the actuator function Diagnostics Pump 30 98 kPa T Desiccant 3 24 2 Weight Cal 1 0000 Dew Offset 0 0000 ayw Pump The pump pressure is only valid when the pump is active When the pump is off the pressure should be between 0 and 0 7 kPa This pressure reading also applies to an auxiliary air supply When the air supply is active the pressure in the system should not exceed 52 kPa If the pump pressure continually reads zero even when you press the switch desiccant button then the pump system may need to be serviced Desiccant The desiccant humidity value indicates the effectivenes
13. Turns the lighting in the desiccant tube area on or off External Gas Enables or disables the use of external gas When External Gas is On the external gas serves as the air source for sample desicca tion and wetting When External Gas is Off the internal pump uses ambient air as the air source Note When you use the external gas it exhausts into the atmo sphere Be sure to provide adequate ventilation and safety measures while using an external gas supply with the instrument Do not use combustible or hazardous gases 33 5 USER INTERFACE AND MENUS AquaLab VSA To turn external gas on highlight External Gas Off and press Enter The External Gas screen appears External Gas Adjust external gas source until pressure is between S and 35 kPa 7 38 kPa F To start using external gas remove the external gas plug from the back of the VSA and insert the desired gas source Adjust the ex ternal gas pressure until it is between 5 and 35 kPa 0 7 to 5 psi The VSA hides the Check Mark until the gas is within the accept able pressure range Press the Check Mark to enable external gas or escape to cancel Note When selecting a gas source choose a gas supply with a filter system that eliminates oil and other particulates to help prolong the life of your VSA Make sure to keep the external gas plug to use when you remove the external gas source If the external gas is turned on in the Configuration tab and you want
14. appear depends on the sample phase changes and stage trigger timeout specifications Press the up or down arrow to view detailed data other than equilibration points 14 PROBLEM Message on the screen indicates that a desiccant tube is low SOLUTION During a test if the VSA determines that a desiccant tube has ex 85 11 TROUBLESHOOTING AquaLab VSA hausted its drying capacity it automatically switches to the other desiccant tube When this event occurs a message appears indi cating that the exhausted desiccant tube needs to be replaced See Section 6 for information on replacing the desiccant tube 15 PROBLEM Screen displays a Low or High System Pressure Warning SOLUTION Anytime the VSA instrument requires air flow it monitors the sys tem pressure and sends a warning if the system pressure is outside the expected range for the current scenario This may be caused by one of several issues 1 External gas flowing when the external gas setting is off 2 External gas not flowing when external gas setting is on 3 External gas pressure outside the recommended range for run ning a test 4 External gas input plug not properly installed or missing when external gas is off 5 Both Desiccant tubes not properly installed or missing 6 Water chamber plug not properly installed or missing 7 Pump system failing If you continue to receive a message after the above items have been checked contact your De
15. physical chemical state and physical structure of the product Consequently the isotherm shape is unique to each product type due to differences in capillary surface and colligative effects Figure 1 Products that lie in the low water activity portion of the isotherm are often referred to as dry those in the range of 0 60 Gy to 0 90 ay are intermediate moisture products and those having water activities higher than 0 90 are high water activity products For ease of interpretation isotherms are often identified by Brunauer classifications Brunauer 1945 Most food and pharmaceutical prod ucts fall under type I II or HI Type I isotherms are typical of very hygroscopic materials Type II sigmoidal isotherms are typical for intermediate moisture products Type III J shaped isotherms are typical for crystalline and coated materials These general classifica tions proved useful when isotherms on every product was not feasible due to time and labor constraints However with automation and improved speed isotherms can easily be conducted on any product and the uniqueness of each isotherm often proves more valuable than placing them in a common classification 3 1 Moisture Sorption Isotherm Methods Constructing an isotherm consists of collecting water activity and moisture content data at various points along the water activity range The range of water activities you use often depends on the situation but normally run from 0 10 a u
16. return to the main menu to make no changes 8 Measure the verification standard again on the Measurement Tab It should read the proper value within 0 005 aw at a given temperature for your particular standard see Appendix A for temperatures other than 25 C 9 Measure the water activity of a second verification standard according to the verification procedure described above If both verification readings are within 0 005 aw then the instrument is ready to begin testing If you still have incorrect verification standard readings after clean ing the chamber and adjusting for linear offset contact AquaLab by email at support aqualab com or by phone at 509 332 5601 for fur ther instructions If you purchased your AquaLab instrument from one of our international distributors please contact them for local service and support Verifying Weight Measurement The VSA uses a magnetic force balance to gravimetrically track the weight of the sample during the isotherm test We verify the perfor mance of this balance against a NIST traceable two gram standard weight This two gram weight ships with the VSA and should be handled with tweezers and not bare skin 54 AquaLab VSA 7 VERIFICATION OF CALIBRATION 1 To verify the balance toggle to the Configuration tab by press ing the Menu icon Scroll down to Diagnostics and press the Enter button to bring up the Diagnostics Screen Diagnostics Lid 25 50 C a Base 24
17. the GAB at characterizing complex isotherms The model equations are shown below 1 ay 1 aule 1 BET m Where m is the moisture in g 100 solids or g g solids at water activity Gy and mg is the monolayer value in the same units Calculate the constant c with s RT Where Qs is the surface interaction energy in J mole R is the gas constant 8 314 J mol K and T K is the temperature c exp Mokpcay GAB an 1 koaw 1 kyu kbcaw Where m is the moisture in g 100 solids or g g solids ky is a constant in the range of 0 70 to 1 and c is a constant in the range of 1 to 2000 In addition m is the monolayer moisture content in the same units as m and aw is the water activity at moisture m DLP m b3 X box bixy bo Where m is the moisture in g 100 solids or g g solids x In In aw and bo b3 are empirical constants Uses for Moisture Sorption Isotherms Moisture sorption isotherms provide valuable information For any one who dries or wets their product the sorption isotherm serves as a drying and wetting curve that provides information about the moisture content of a product when dried or wetted to a specific wa ter activity Customers can use the sorption isotherm to assist in process control by determining drying rates and optimal endpoints If a product exhibits hysteresis the isotherm shows what impact the hysteresis has on the moisture content after drying to a given
18. to turn it off pressing enter causes the External Gas screen to appear External Gas Turn off gas source and reinstall gas input plug 0 19 kPa E To stop using external gas turn off the external gas source and re move the external gas tubing and adapters from the back of the in strument Reinstall the external gas plug and then press the Check 34 AquaLab VSA 5 USER INTERFACE AND MENUS Mark to disable external gas or the X to return to the Configuration tab without changing the setting Contrast Allows you to set the contrast of the screen to your liking View ing the screen from a sitting versus a standing position may require contrast adjustment for the best visibility in that position Contrast Use the up and down arrows to change the contrast 3 Al Diagnostics The Diagnostics screen provides you with detailed information about all the sensors in the instrument Refer to the Troubleshooting sec tion for details on what kind of values you should expect for each sensor Press up or down to page between the different Diagnostics screens Diagnostics Lid 25 50 Base 24 99 Sample 25 12 Mirror 25 557 ETA ETE aS The scale icon on the bottom of the second screen allows you to zero the balance so that you can take weight readings via the diagnostic screen The icon labeled Act toggles the actuator system on and off With the lid open pressing this button causes the weigh pan
19. with the Date option highlighted to set the date in the instrument Press the left and right arrows to change between the month day and year Press the up or down arrows to change any of the individual values 29 5 USER INTERFACE AND MENUS AquaLab VSA Date Aug 01 2011 A x 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 Time 2 48PM A x dy Settings Settings related to water activity measurements can be updated here These include default system temperature temperature equilibration tolerance and beeps ay Settings Temperature 25 0 C a Temp Eq lt 44 0 C x Beeps 4 al 4 30 AquaLab VSA 5 USER INTERFACE AND MENUS Temperature This setting determines the temperature that the instrument main tains during water activity measurements It is also the temperature that the instrument returns to after completing a test The default temperature is 25 C Press the Enter button to change the temper ature setting You can set the VSA anywhere between 15 and 60 C in 0 1 C intervals Use the up and down arrows to set the VSA to your desired temperature Temp Eq Temperature Equilibration Tolerance or Temp Eq sets the max imum di
20. 0 4 Hew FF lt lt e 9 To setup a new stage select New and press the Enter button If more than one stage is in memory you have the option of inserting the stage after any existing stage in the test A screen with several parameters appear If you ran a previous test the stages for that test list by default You can use these stages as is or update them with new settings If you need to delete or edit a stage go to the specific stage press the Enter button and then select Edit or Delete 10 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 stage 1 Type DOI Start 0 100 a Final 0 700 ay Temperature 25 0 C s S 4 For the DDI method 1 To choose the starting aw highlight Start press the Enter button and then cycle to the desired value using the up and down arrows You can choose any value between 0 03 and 0 95 Qw including current Choosing current causes the stage to begin at the initial a of the sample Press the Save button when finished 63 8 RUNNING A TEST AquaLab VSA 2 To choose the final aw highlight Final press the Enter but ton and then cycle to the desired value using the up and down arrows You can chooses any value between 0 03 and 0 95 ay including current Selecting a final aw that is lower than the starting a
21. 3 Download and Export 1 Once you connect the VSA after a test has been run a down load of the test starts automatically If not select Download in the toolbar Note It is strongly recommended to save the test vsa before continuing 2 From the File menu or using the icon in the toolbar select Export to create an Excel compatible table 3 To view your data in table format click the Table button in the toolbar 4 To view your data in chart format click the Chart button in the toolbar While the Moisture Analysis Toolkit does not have a User s manual extensive help files exist to guide you through the various features and processes of Moisture Analysis Toolkit To find these help files in the Moisture Analysis Toolkit click on the Help menu item and then select the Moisture Analysis Toolkit Help submenu item to display the help files 73 10 SAMPLE PREPARATION AquaLab VSA 10 Sample Preparation Proper sample preparation is an important step in keeping your VSA clean and achieving repeatable results Careful preparation and load ing of samples lengthen the time needed between cleanings and help to avoid downtime 10 1 Preparing the Sample 1 Make sure the sample to be measured is homogeneous Multi component samples or samples that have outside coatings can be measured but results may vary based on sample prepara tion methods Some samples types need special preparation see Section 10 2 2 P
22. 7 shows the proper method of installing Desiccant tubes Before insertion make sure to firmly seal the desiccant tube lid onto the desiccant tube and remove the black vinyl covers from the air fittings Lift the desiccant tube into the area above the desiccant receiver and then insert the fittings into the mating holes Be sure to place the black fitting into the corresponding black hole Once in place the desiccant tube is sealed for flow purposes even if it may feel loose 21 4 GETTING STARTED AquaLab VSA Figure 7 Desiccant Installation 5 Install the air cylinder and weighing pan With the lid open insert the air cylinder and weighing pan into the testing block as shown in Figure 8 These parts should remain in the instrument continually and are only to be removed for maintenance Do not insert a sample cup unless you are running a test Place the air cylinder into the base block bore It should slide into the block easily and settle at the bottom of the bore The weigh pan connects to the scale and holds the sample cup For best results verify cleanliness of all parts and avoid dropping the parts as damaged parts may not slide properly and affect performance 6 Verify shipping did not damage the scale performance and test scale stability a Turn on the VSA and wait for it to warm up Note The scale takes about two hours after power up to come to full equilibrium b Go to the Configuration menu navigate to the
23. A for the correct water activity value of 5l VERIFICATION OF CALIBRATION AquaLab VSA 10 Decagons standards at temperatures other than 25 C If your VSA is reading within 0 005 aw of the verification standard choose a 0 76 aw standard Prepare a sample cup of the second verification standard and make two readings The second water activity reading for the second verification standard should be within 0 005 aw If either of the verification standards is not correct it is prob ably due to contamination of the sensor chamber See Section 6 for cleaning instructions After cleaning repeat verification from step two If you are consistently getting readings outside the water activ ity of your first verification standard by more than 0 005 ay a linear offset has probably occurred In this case adjust the reading to match the correct value of the verification standards this section outlines Measure Verification Standard start with primary standard Repeat Process Clean Sample Clean Sample Chamber Chamber Re Read First Read Second Standard Standard Go to Offset Go to Sampling Procedure Procedure See the verification section in the operator s manual Figure 15 Measure Verification Standard Flowchart 52 AquaLab VSA 7 VERIFICATION OF CALIBRATION Adjust for Linear Offset for Water Activity 1 Once you are certain a linear offset has occurred toggle to the Configurat
24. EORY AquaLab VSA directly measures water activity while gravimetrically tracking weight so there is no dependence on equilibration to known water activity levels to determine water activity Adsorption occurs as saturated wet air passes over the sample Desorption happens as desiccated air passes over the sample After a short period of time the VSA halts airflow and takes a snapshot of the sorption process by directly mea suring the water activity and weight The advantages of this method include increased analysis speed as the sample does not have to wait for equilibration to a known water activity and an unmatched level of resolution This makes it possible for dynamic isotherms to produce high resolution isotherms in a matter of days instead of the weeks it would take to make a comparable isotherm using equilib rium techniques The high resolution of dynamic isotherms makes them valuable for observing sudden changes in sorption properties associated with matrix changes such as glass transition The dynamic nature of the DDI method means that moisture con tents may or may not be at equilibrium and it is possible for there to be differences between dynamic and equilibrium isotherms For sam ples with fast vapor diffusion penetration by water vapor into the whole sample is rapid and isotherms using the DDI method for these types of products are comparable to equilibrium methods However for samples with slow diffusion rates moisture mov
25. NING AND MAINTENANCE 6 Cleaning and Maintenance 6 1 Desiccant Cartridge Desiccant Replacement 1 Removal of the desiccant material a Orient the desiccant cartridge or tube Figure so the lid or cap is up b Remove the main lid c Remove the foam located below the lid as shown in Fig ure d 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 e Pour out the desiccant material Wash out the lid and washer Figure 12 Ensure no pieces of desiccant stick to the lid and shake off any excess water Figure 11 Desiccant Cartridge Foam Figure 10 Desiccant Cartridge 2 Loading the desiccant into the desiccant cartridge 41 6 CLEANING AND MAINTENANCE AquaLab VSA YN Q nee e i i Orient the desiccant tube so the opening is upward Hold the tubing to the side of the cartridge and looped over the edge of the cartridge Fill the desiccant to the top of the cartridge Shake or vibrate the desiccant cartridge to settle the ma terial The top of the desiccant should be about 0 1 inches from the cartridge rim If not add more desiccant and settle until it reaches 0 1 inches Place in the foam at the top Place the small tubing across the filter and through the slit in the foam Figure 11 Wet the cartridge bottle lip and the edge of the washer adjace
26. Press the Enter button to begin testing Note If you decide at this point not to continue with the linear off set program just return the lever to the Open position or press X to return to the previous screen 6 After your VSA has finished measuring the weight verification it displays the test value 56 AquaLab VSA 7 VERIFICATION OF CALIBRATION 7 Press Save to adjust to the correct value To cancel and return to the main menu press the Cancel button and no changes 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 How to Restore Factory Defaults Follow steps 1 through 4 to restore original calibration settings 1 Toggle to the Configuration tab by pressing the Menu icon Select Calibration and press the Enter button 2 Select water activity or weight depending on which defaults you want to restore and press Enter 3 Scroll down to Defaults and press the Enter button to access the Restore Factory Defaults routine To cancel and return to the main menu select the Cancel icon After selecting the Enter icon the Calibration a screen prompts you to reset to defaults Calibration a Reset to defaults aA 38 4 To restore the factory calibration values
27. SA 8 RUNNING A TEST value using the up and down arrows You can select any value between 5 0 minutes and 30 days The timeout determines the maximum time allotted to move from the starting ay to the final aw DDI only and is optional The default value is off which means there is no timeout value 7 To choose to have the isotherm loop highlight Loop and press the Enter button to toggle between on and off Turn ing loop on causes the isotherm to automatically return to the starting a with the same settings once the final aw has been achieved This would create both an adsorption and desorption curve or vice versa depending on the starting direction 8 When finished adjusting the settings for the stage press the Save button to save and return to the Edit Stage screen Press Cancel to return to Edit Stage screen without saving changes stage 1 Start 0 100 a Final 0 700 ay Temperature 25 0 C al e For the DVS Method 1 To choose the starting ay highlight Start press the Enter button and then cycle to the desired value using the up and down arrows You can choose any value between 0 03 and 0 95 Gy including current Choosing current means that the stage starts at the initial a of the sample Press the Save button when finished 2 To choose the final aw highlight Final press the Enter but ton and then cycle to the desired value using the up and down arrows You can choos
28. Vapor Sorption Analyzer Operator s Manual Decagon Devices Inc Version December 15 2015 13 32 16 AquaLab VSA Decagon Devices Inc 2365 NE Hopkins Court Pullman WA 99163 Phone 509 332 5601 Fax 509 332 5158 Website www aqualab com Email support aqualab com or sales aqualab com Trademarks AqualLab is a registered trademark of Decagon Devices Inc 2008 2015 Decagon Devices Inc ii AquaLab VSA CONTENTS Contents 1 1 Customer Support 004 1 2 About ThisManual 1 3 Warranty 0 002000 eee 1 4 Seller s Liability 2 0 20 20 2 2 048 2 About the VSA 2 1 Moisture Sorption Isotherms 2 2 Measurement Method 2 3 AquaLab Vapor Sorption Analyzer Specifications 3 Theory 3 1 Moisture Sorption Isotherm Methods 4 Getting Started 4 1 Instrument Setup 2 20 4 5 User Interface and Menus 5 1 Isotherm Tab 0000 5 2 Measurement Tab 08 5 3 Configuration Tab 2 04 5 4 Data lab lt eaae oe GB a EA eR A eb a 6 1 Desiccant Cartridge Desiccant Replacement pees i aaas a 2 OG dew amp oR Rae Se oe Sp Pee bo eee eS 7 2 Verification Standards 0 7 3 When to Verify for Linear Offset 7 4 Isotherm Standard Comparison 8 Running a Test 8 1 Becoming Familiar wi
29. When to Verify for Linear Offset Check the linear offset against two known verification standards be fore running a new isotherm test Never verify the linear offset solely against a single standard since it does not give an accurate rep resentation of the linear offset For best results conduct the VSA water activity verification using the 0 25 a and 0 76 ay standards Checking the water activity of a standard solution can alert you to the possibility of unit contamination or shifts in the linear offset from other causes Note The verification process is the same whether you set the volatiles to yes or no except that the accuracy for the capacitance sensor is 0 020 Qw Verification Use steps 1 through 10 to verify for linear offset of your VSA Refer to the Measure Verification Flowchart in F igure 15 1 From the Isotherm Tab navigate to the Measurement tab by pressing the Enter button 2 Choose a 0 25 a standard 3 Remove the weighing pan 4 Empty a vial of solution into the stainless steel sample cup and place it in the VSA testing chamber Make sure that your standard is as close to the instrument temperature as possible Section Note Make sure the rim and outside of the sample cup are clean 5 Carefully close the lid and move the lever to the READ posi tion 6 Take two readings The water activity readings should be within 0 005 aw of the given value for the verification stan dard See Appendix
30. able For the most accurate verification of your VSA performance we recommend the verification standards that Decagon Performance Verification Standards come in six water activity lev els and 0 250 0 500 0 760 0 920 0 984 and 1 000 aw We produce these standards under a strict quality assurance regime Please con tact Decagon Devices to order additional standards or order them via the web at http www aqualab com reorder Note To avoid inaccurate water activity readings verification stan dards should be used once immediately after opening and not stored in sample cups for repeated use Table 1 Verification Flowchart Verification Standard 25 C Water Activity 13 41 mol kg LiCl 0 250 0 003 8 57 mol kg LiCl 0 500 0 003 6 00 mol kg NaCl 0 760 0 003 2 33 mol kg NaCl 0 920 0 003 Note If you need to obtain a Safety Data Sheet SDS for any of these standards a printable version is available on our website at http www decagon com education safety data sheets Although distilled water and the 0 984 standard are available as a verification standard Decagon does not recommend using them 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 Customers can find information about standard values and molality printed on the outside of the plastic vial 50 AquaLab VSA 7 VERIFICATION OF CALIBRATION 7 3
31. ach step or by inducing changes in the water binding properties of the matrix by wetting or drying We prefer to treat these cases separately and re serve the term hysteresis for situations where equilibrium is reached but water contents of wetted and dried samples still differ because of their history There are four primary models for hysteresis These theories em phasize capillary condensation of porous solids phase changes of non porous solids structural changes within a solid matrix and su persaturation of some solutes during desorption Depending on the composition of the sample these theories explain why the water con tent of a desorption process is greater than that for a wetting process 1 The ink bottle model illustrates the capillary condensation of porous solids theory in which pores and capillaries fill and empty differently Such a pore fills when the water activity 12 AquaLab VSA 3 THEORY corresponding to the energy state of the larger radius is ex ceeded but empties only when the water activity drops below the energy state of the narrow neck radius 2 A phase change of non porous solids is illustrated by the fact that desorption from rubbery state can reach equilibrium faster due to increased molecular mobility while adsorption into a glassy material can be slow due to restrictions in molecular mobility 3 Structural changes within a solid matrix occur when the ma terial swells and polar s
32. alue and only the trigger value determines the end of step If both a trigger value and timeout value are set whichever is reached first determines the end of the step 6 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 aw with the same settings once the final aw has been achieved This would create both an adsorption and desorption curve or vice versa depending on the starting direction 7 When finished adjusting the settings for the stage press the Save button to save and return to the Edit Stage screen Press the Cancel button to return to Edit Stage screen without saving changes 67 8 RUNNING A TEST AquaLab VSA 10 11 12 8 3 After setting up all stages on the Edit Stage screen select the double Right arrow Follow the message on the screen to place an empty stainless steel cup in the chamber and seal it Press the double right arrow to tare the cup Follow the message on the screen to place the sample in the cup and select the double right arrow to weigh the sample When filling the sample cup remove the cup from the chamber to avoid spills in the chamber area Press the Enter button to begin the test Using DDI to investigate Glass Transition To investigate glass transition events using dynamic isotherms a DDI test with the settings of initial wate
33. an provide you with local support and service When encountering problems with your VSA that you are unable to resolve with the help of this manual please contact Decagon Cus tomer Support at support aqualab com 509 332 5601 or fax us at 509 332 5158 Please have the serial number and model of the in strument ready AquaLab annual calibration is available For details on sending your AquaLab to Decagon or your distributor in for calibration contact us by phone or email at support aqualab com All instruments returning to Decagon for servicing must be accom panied with a Return Material Authorization RMA number Prior to shipping the instrument please contact a Decagon customer sup port representative to obtain an RMA number Shipping Directions The following steps should help to ensure the safe shipping and pro cessing of your VSA 1 Ship the VSA in its original cardboard box with suspension packaging Failure to ship in proper packaging can damage the scale and void the warranty 2 Do not ship the power cord or serial cable and be sure the water tank is empty 3 Remove the desiccant tubes and wrap them in bubble wrap to include with your VSA 4 Remove the weight pan and air cylinder wrap both separately to prevent damage 5 On the RMA form please verify the ship to and bill to infor mation contact name and problem description If anything is 94 AquaLab VSA 12 SUPPORT AND REPAIR incorrect ple
34. an the chamber and run charcoal before switching to the dew point sensor Low Water Activity When a sample water activity is below the cooling capacity of the chilled mirror the VSA displays a less than symbol or gives a low water activity message in the software If the error persists see the troubleshooting section 76 AquaLab VSA 11 TROUBLESHOOTING 11 Troubleshooting The AquaLab VSA is a high performance and low maintenance in strument that Decagon Devices Inc has designed to have few prob lems if customers use their instrument with care and follow the proper procedures in this Operator s Manual Unfortunately even the best operators using the best instruments encounter technical difficulties on occasion Table 2 provides a quick reference table for the troubleshooting guide to direct you to detailed solutions for some of the problems that may occur with your VSA This section lays out the most common prob lems and solutions for your troubleshooting needs following the quick reference table If these remedies still do not resolve your problem then please contact Decagon for help at support aqualab com When contacting support for an issue be sure to include your contact information Name Title Company Phone Number the instrument serial number and a short description of your issue Note Please ensure that you read through the troubleshooting por tions thoroughly before contacting Decagon for assistance
35. and actuator cylinder to alternatively rise and fall if working properly 35 5 USER INTERFACE AND MENUS AquaLab VSA Diagnostics RH 239s 22783 Weight 1565 6 mg Optical S06 ri y Latch Closed atl aE a 1H On startup the pump is turned on and flows dry air into the cham ber to monitor the desiccating capacity of the tubes The number button on the bottom screen allows you to switch between the two desiccant tubes If you press the number button with the arrow 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 Diagnostics Fump 30 48 kPa Desiccant 32x 2 Weight Cal 1 0000 Dew Offset 0 0000 ayw The weight calibration value is the current calibration applied to balance readings A value of one means no weight calibration is applied The dew point and capacitance RH sensor offset values are the current linear offsets applied to water activity readings for the respective sensor type A value of zero means that the VSA applied no water activity offset 36 AquaLab VSA 5 USER INTERFACE AND MENUS Diagnostics Cap Offset 0 0015 aw a About The About screen provides important information including the se rial number and firmware
36. ase contact a Decagon representative 6 Tape the box in both directions for added support 7 Include the RMA number in the attention line on the shipping label Ship to Decagon Devices Inc ATTN RMA insert your RMA 2365 NE Hopkins Court Pullman WA 99163 12 1 Repair Costs Decagon Devices repairs manufacturer defects and instruments within the one year warranty at no charge We charge you for non warranty repairs based on cost of parts labor and shipping An extra fee may be charged for rush work Decagon can provide an estimated repair cost upon request 95 13 APPENDIX A AquaLab VSA 13 Appendix A Temperature Correction of Decagon s Verification Standards Table 3 Water Activity of Selected Solutions 0 50 2 33 6 00 8 57 13 41 Temp H2O mol kg mol kg mol kg mol kg mol kg C KCL NaCL NaCL LC Lidl 10 0 1 000 0 984 0 923 0 762 0 491 0 234 15 0 1 000 0 984 0 923 0 761 0 492 0 238 20 0 1 000 0 984 0 922 0 760 0 496 0 245 25 0 1 000 0 984 0 920 0 760 0 500 0 250 30 0 1 000 0 984 0 920 0 760 0 504 0 255 35 0 1 000 0 984 0 920 0 760 0 508 0 261 40 0 1 000 0 984 0 921 0 760 0 512 0 266 50 0 1 000 0 984 0 894 0 740 0 517 0 275 60 0 1 000 0 984 0 894 0 740 0 505 0 279 Note The AquaLab VSA measures these verification standards to 0 005 Aw 96 AquaLab VSA 14 APPENDIX B 14 Appendix B Non Condensing
37. ated 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 Increase the flow rate 3 Water tank has run dry 4 Desiccant cartridge has been used up 25 PROBLEM Scale readings are not stable or the sample cups cannot be tared 89 11 TROUBLESHOOTING AquaLab VSA SOLUTIONS 1 Unstable bench or support for the VSA 2 Air cylinder internal parts need to be cleaned Lift out air cylinder and clean 3 Interior parts have shifted and are contacting so air cylinder does not slide 4 Verify actuation using ACT Button in diagnostics as described in Section 5 26 PROBLEM Scale calibration is failing SOLUTIONS 1 Air cylinder and internal parts need to be cleaned 2 Air cylinder is not actuating May be sticking due to contami nation in chamber 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 2 Check that external fan on the back of the unit is operational 90 AquaLab VSA 11 TROUBLESHOOTING 11 1 Diagnostics Screen If after cleaning your instrument and reading the other troubleshoot ing hints you have reason to believe that one of the components of your VSA may be causing mea
38. cagon representative for further options 16 PROBLEM Screen displays Power was reset Error Fower was reset 86 AquaLab VSA 11 TROUBLESHOOTING SOLUTION If the VSA instrument resets because of a power outage at any time during a test or due to unforeseen circumstances this message appears on the screen If Auto Restart is turned on the test au tomatically resumes after a device reset If Auto Restart is turned off then the test stops running following a device reset To prevent device resets Decagon strongly recommends that you connect your VSA to an Uninterruptible Power Supply UPS 17 PROBLEM Screen indicates a scale failure overload or underload SOLUTION If the VSA is unable to communicate with the scale the scale failure message appears If the scale is reading overload or underload then the balance is either misaligned or broken If any of these instances occur Decagon needs to service your VSA 18 PROBLEM Screen displays Actuator failure SOLUTION An actuator failure occurs when the air cylinder cannot actuate 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 19 PROBLEM Message on the screen displays a critical error while starting the test
39. ced by Decagon See Section 12 for detailed instructions 7 PROBLEM Verification is not correct SOLUTION 1 The sample chamber and mirror need to be cleaned See Sec tion 6 for detailed cleaning instructions If verification is still not correct then linear offset has occurred 2 Verify and Adjust for Linear offset After you have cleaned the sample chamber and mirror use a Verification Standard to verify and adjust for Linear offset Section 7 8 PROBLEM Message on screen displays Crystal Failure 82 AquaLab VSA 11 TROUBLESHOOTING Error Crystal Failure See Manual for options SOLUTION The crystal that runs the firmware is having trouble starting Oc casionally cycling the power can solve this problem If this message continues to appear Decagon needs to service the instrument See Section 1 3 for instructions on warranty and contact information 9 PROBLEM Message on screen displays Contaminated mirror Errar Contaminated mirror SOLUTION The mirror used for dew point measurements requires cleaning Fol low the instructions outlined in Section 6 Cleaning and Maintenance before trying to run your sample again If this message continues to appear contact your Decagon Representative for further options 10 PROBLEM Message on screen displays the error Firmware is corrupted 83 11 TROUBLESHOOTING AquaLab VSA Errar Firmware is corrupted See Man
40. claration of Conformity Application of Council Directive 2004 108 EC and 2011 65 EU Standards to which conformity is EN 61326 1 2013 and declared EN 50581 2012 Manufacturer s Name Decagon Devices Inc 2365 NE Hopkins Ct Pullman WA 99163 USA Type of Equipment AquaLab Vapor Sorption Ana lyzer Model Number VSA Year of First Manufacture 2011 The undersigned hereby declares on behalf of Decagon Devices Inc that the above referenced products to which this declaration relates fully conform to the provisions of the Council Directives and stan dards referenced above Ilek B V adowra Michael Wadsworth Engineering Director 7 9 2015 98 AquaLab VSA 16 CERTIFICATE OF TRACEABILITY 16 Certificate of Traceability Decagon Devices Inc 2365 NE Hopkins Court Pullman WA 99163 USA Tel 509 332 5601 Fax 509 332 5158 support Aqualab com This NIST seal certifies that Decagon Inc manufactures all AquaLab water activity meters according to temperature standards with cal ibration traceable to the National Institute of Standards and Tech nology NIST National Institute of Standards and Technology NUT Your AquaLab is calibrated to a NIST traceable temperature standard 99 Index Annual Calibration Service Aqualab VSA Information Balance Magnetic Force Calibration Verification of Certificate of Traceability Cleaning Procedures Block and Sensors Testing Chamber Co
41. code version of your instrument About SM WSAL234 Version WSA 1 30 2011 DECAGON Decagon Devices Inc 5 4 Data Tab The Data tab allows you to view detailed information about the test stored in the 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 the memory Data T 44an Delete 177710000 4 37 5 USER INTERFACE AND MENUS AquaLab VSA View This selection brings you to a screen where you can decide how you want to view your data You can choose to view your whole test at once by selecting All or you can view an individual stage Once the desired portion of the test is selected you can then choose to graph the data by pressing the graph icon or by pressing the enter icon to view summary information of each data record See Section 9 for information about downloading test data to a computer Wiem 2DVS 0129 ap 0 550 ay AII k 1 DwS 0 150 a 0 350 a ZDS 0 204 ai 7504 x Graph Screen This selection shows a graph of the selected data from the previ ous 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 Example of a graph with water activity as the x axis MCC DDI Dew Foint 1 4 35PH BOY 4m3 o DDI Example of a graph with elapsed time as the x axis
42. ded allowing for determining kinetics of sorption for each humidity level Using less stringent equilibrium settings for weight change or setting a re duced time interval at each step can speed up the isotherm test but may give non equilibrium results In addition setting smaller steps in humidity increase the data resolution of the isotherm but at the expense of much longer test times The VSA is a stand alone instrument with an integrated pump sys tem that eliminates the need for an external gas cylinder however you can use an external gas source if desired The instrument con sists of a case which houses the power supply air pump balance temperature controlled sample chamber sensor block sensor and temperature control electronics water reservoir and desiccant sup ply 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 2 3 AquaLab Vapor Sorption Analyzer Specifications Water Activity Relative Humidity Range 0 03 to 0 95 aw 3 to 95 RH Water Activity Relative Humidity Accuracy 0 005 aw 0 5 RH for volatiles setting 0 02 aw 2 RH Water Activity Relative Humidity Resolution 0 0001 aw 0 01 RH 0 001 a 0 1 RH for volatiles setting Water Activity Relative Humidity Repeatability 0 003 a 0 3 RH for volati
43. e Operator s Manual e Quick Start Guide e Calibration certificate SDS certificates e Power cord e USB interface cable e Two stainless steel sample cups e Three refillable desiccant tubes e One Decagon cleaning kit e Two water bottles e Three vials each of the following verification solution 0 250 ay 13 41 mol kg LiCl 0 500 ay 8 57 mol kg LiCl 0 760 aw 6 00 mol kg NaCl 0 920 ay 2 33 mol kg NaCl e Moisture Analysis Toolkit Software Package with Registration Key e One 2 g NIST traceable weight e Tweezers Note Please keep your original instrument shipping box If you ever need to return your VSA you must ship it in the original packaging 20 AquaLab VSA 4 GETTING STARTED 4 1 Instrument Setup 1 Place AquaLab VSA on a flat and stable surface Use the bubble level Figure 6 and the adjustable feet to level the instrument The small rubber feet on the back of the lower plate prevent tip over and do not need to be touching the table 2 Use AquaLab VSA where environmental temperature and hu midity remain stable and are non condensing See Appendix B 3 Plug in AquaLab VSA and turn on the power switch in back For best results let the instrument warm up for two hours before use Adjustment feet two on front and one on the middle back Figure 6 Adjustment and Bubble Level 4 Install the two desiccant tubes in the front of the instrument Figure
44. e any value between 0 03 and 0 95 ay including current see current definition above Selecting a fi nal ay that is lower than the starting a results in desorption 65 8 RUNNING A TEST AquaLab VSA while selecting a final ay higher than the starting aw results in adsorption Press the Save button when finished 3 To choose the temperature of the stage highlight Tempera ture press the Enter button with Temperature highlighted and then cycle to the desired temperature using the up and down arrow keys You can choose any temperature between 10 and 60 C and each stage can run at a unique temperature 4 To choose the desired ay step highlight Step press the Enter button and then cycle to the desired value using the up and down arrows You can choose any value between 0 003 and 1 0 ay The step setting for DVS determines the a values for equilibration and consequently the resolution A step setting of 0 10 a with a starting value of 0 1 a results in humidity being controlled to 0 1 0 2 0 3 up to the final aw remaining at each level until either equilibrium is achieved based on the trigger value or reaching the timeout value Setting a higher value makes the test faster but decreases the a resolution stage 1 Steo 0100 Trigger Off Timeout OFF Loop On lr S e To choose the trigger dm dt value that indicates equilibra tion highlight Trigger press the Enter button to
45. e remaining from the cleaning e Visually inspect the mirror for cleanliness Clean again if necessary 3 Clean the Thermopile and Optical Sensor a Wrap a new Kimwipe around the end of the spatula and moisten it with Decagon Cleaning Solution b WASH Swipe the moistened Kimwipe across thermopile and optical sensor A single swipe across the sensor is usually sufficient to remove contaminants c RINSE Repeat steps a and b using new Kimwipes moistened with USP Purified water instead of cleaning solution d DRY Repeat steps a and b but use a new dry Kimwipe 47 6 CLEANING AND MAINTENANCE AquaLab VSA to help remove any moisture remaining from the cleaning e Visually inspect the thermopile and optical sensor for clean liness Clean again if necessary 4 Additional Drying Time a Visually inspect the sample chamber and sensors for con taminants including moisture If necessary repeat the cleaning process using new Kimwipes b Leave the chamber open for about five minutes to ensure the sample chamber is dry 48 AquaLab VSA 7 VERIFICATION OF CALIBRATION 7 Verification of Calibration After you have cleaned the chamber and other parts of your VSA it is important to check the instrument performance in order to correct for any linear offset that may have occurred Before you check the instrument we recommend that you measure a sample of the activated charcoal pellets provided in
46. ea Section outlines the cleaning steps Wash your hands with soap and water and use clean lab gloves before starting the cleaning procedure This prevents oils from contaminat ing the cleaning materials the sample chamber and the sensors 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 consists of all surfaces within the red o ring when the lid is closed Follow the cleaning procedures and do not get cleaning solution or al cohol on the capacitance sensor filter Repeated exposure of cleaning materials or contaminants to the filter may cause inaccurate read ings If the filter appears to be contaminated it may need to be replaced To replace the capacitance sensor filter use tweezers or a small knife blade to pry up the edge of the filter being careful not to disturb the sensor beneath Discard the soiled filter and with clean or gloved hands press a new filter into place 45 6 CLEANING AND MAINTENANCE AquaLab VSA Upper Block Thermopile O Ring Capacitance 7 Filter Mirror Fan Optical d Check Sensor Valves Sample Lower Pan Block Figure 14 Sample Chamber Breakdown 6 3 Cleaning Procedures Visit www aqualab com cleaning for a cleaning video tutorial 1 Cleaning the Sample Chamber Note Be extremely careful not to damage t
47. ect End Current Stage press Enter to make a Check Mark appear and click the Save button The current stage ends and the newly created stage begins Note To edit a test using the software see the Moisture Analysis Toolkit software in Section 9 8 6 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 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 If you set volatiles to yes as described in Section the VSA determines water activity readings using the capacitance sensor otherwise it uses the dew point sensor 1 From the Measurement tab move latch left and and reading starts automatically The pinwheel spins when taking a mea surement Pressing the Enter button also starts a reading 2 The ay reading for the sample and the temperature displays when the VSA finishes 3 Toggle the Volatiles Yes No option in the Configuration menu to change between dew point and capacitive readings Volatiles 70 AquaLab VSA 8 RUNNING A TEST Yes Capacitive Sensor Volatiles No dew point Sen sor 71 9 MOISTURE ANALYSIS AquaLab VSA 9 Moisture Analysis Toolkit Software While the AquaLab VSA can operate as a stand a
48. ement through the sample is slow and complete diffusion of moisture into and out of the sample may be slow enough to give the appearance of vapor equilibrium in the headspace during water activity analysis In re ality the moisture has not had time to be completely absorbed by the sample Isotherms for these types of samples developed using the DDI method may have lower moisture contents during adsorp tion and higher moisture contents during desorption than equilibrium isotherms resulting in higher levels of apparent hysteresis 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 disad vantages While the data they generate agrees in some cases it 10 AquaLab VSA 3 THEORY is the uniqueness of the results from each method that gives them value There is information that can only be obtained from dynamic isotherms such as critical water activities for glass transition Simi larly there is information that can only be obtained by equilibrium isotherms such 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 Hysteresis Figure 2 shows two isotherms one obtained by wetting a sample
49. ent desic cant must be 10 to 20 mesh 43 6 CLEANING AND MAINTENANCE AquaLab VSA 6 2 Cleaning the Testing Chamber Keeping your VSA clean is vital to maintaining the accuracy of your in strument Dust and sampling debris can contaminate the sampling cham ber and must be regularly cleaned out Purpose The cleaning procedure removes grease dirt and other soluble substances that can absorb or release water during verification calibration and sample testing The mirror must be clean for a smooth and even dew formation Any contaminants e g fingerprints on the mirror can cause the dew to form unevenly and affect the accuracy of the read ing Figure 13 Checking Desiccant Cartridge for Leaks When to Clean The instrument should be cleaned if visual inspection indicates the chamber is dirty or as instructed in the verification flowchart Fig ure 15 We recommend cleaning before each new isotherm test Required Cleaning Materials A thin plastic rod or other non metal implement USP Purified Water Isopropyl Alcohol IPA or AquaLab Cleaning Solution Kimwipes You may also purchase the AquaLab Cleaning Kit which comes with all the above materials except the Isopropyl Alcohol The materials in the kit should last for about one year 44 AquaLab VSA 6 CLEANING AND MAINTENANCE Before you begin Cleaning your VSA is a multi step procedure which involves washing rinsing and drying for each ar
50. equipment con stitutes Buyer s acceptance of the terms set forth in this warranty There are no understandings representations or warranties of any kind express implied statutory or otherwise including but with out limitation the implied warranties of merchantability and fitness for a particular purpose not expressly set forth herein 2 ABOUT THE VSA AquaLab 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 aw and moisture content at a given temperature This re lationship is complex and unique for each product due to different interactions colligative capillary and surface effects between the water and the solid components at different moisture contents An increase in a almost always accompanies an increase in water con tent but in a non linear fashion Moisture sorption isotherms are sigmoidal in shape for most foods although foods that contain large amounts of sugar or small soluble molecules have a J type isotherm curve shape Isotherms provide information about product quality and safety A few uses for isotherms include 1 Monolayer moisture content determination 2 Determine critical water activity or moisture content 3 Limits for crispness hardness and flow p
51. esiccant level 5 The Edit Test screen appears 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 The name of a previous test appears by default 61 8 RUNNING A TEST AquaLab VSA Edit Test Name ACC Initial MC Hone lt lt e 6 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 The wb refers to the moisture reporting basis which can be either wet basis wb or dry basis db The moisture content basis is set as a global preference in the Configuration tab see Section 5 Press the double right arrow to continue or the double left arrow to go back Initial AC 15 0 ub A x 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 set up with the isotherm method DDI or DVS and the settings for that portion of the isotherm Once you create a stage you can modify or delete it anytime before you begin the test 8 For example for milk powder Stage One could use the DDI method to ramp quickly from 0 1 to 0 4 aw and Stage Two could use the DVS method to step from 0 4 to 0 8 ay slowly in 0 05 aw increments 62 AquaLab VSA 8 RUNNING A TEST Edit Stages 1 001 0 100 a 0 70
52. f hysteresis The boundary isotherm with a 0 80 aw maxi mum experienced a phase change at 0 43 aw indicated by a sharp inflection point in the curve The desorption curve for this isotherm appears to show hysteresis especially below 0 60 aw However an isotherm run on a sample wetted to a maximum water activity be low the phase change exhibits very little hysteresis The lack of hysteresis in this isotherm indicates that the matrix changes that oc cur at 0 43 ay are completely responsible for the apparent hysteresis Various bonding mechanisms bind water in a sample to particle sur faces When the configuration of particle surfaces changes due to a phase change binding sites change and the amount of water which can be bound at a given energy of water also changes An isotherm curve of the phase changed sample does not show further phase tran sitions since simply drying the sample does not return it to an amor phous state These matrix changes represent a true physical change in the ma terial They are not reversible by drying no matter how many dry ing cycles occur Differences between the adsorption and desorption curves in the initial isotherm is not true hysteresis since the sam ple matrix has experienced a physical change Differences between sorption curves in the subsequent isotherms represent true hysteresis 14 AquaLab VSA 3 THEORY Moisture Content d b 0 0 2 0 4 0 6 0 8 1 Water Activity
53. fference 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 4 C is the default setting Beeps Indicates the number of audible beeps after a water activity measure ment is completed You can set this value to off 0 4 or infinity 00 Regional Formatting Allows you to configure how the VSA displays 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 Press Enter to switch the setting Regional Formatting Teagerenrar x Time 12h Language English H 5 USER INTERFACE AND MENUS AquaLab VSA Admin Settings Allows you to create an administrator password as well as add edit and delete additional users The Admin option allows the admin istrator to grant or block access to some or all of the configuration options For example if the administrator wanted to make sure that all samples were read at 25 C the administrator would set their temperature to 25 C and then would lock all other users out of that Configuration screen This is accomplished by entering the Access function and selecting the desired option to toggle it on and off Ad ditionally you can lock and u
54. 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 This phenomenon is called hysteresis The curves in Figure represent limits or boundary isotherms since they begin at water activities near zero and one If a drying process reduces the water activity of a sample only part way to dryness and the sample is then wet again it follows a path between the wetting and drying bound ary curves as shown in Figure 3 These curves are called scanning curves and there can be an infinite number of them depending on where drying stops and starts 9 8 3 6 Z 5 5 a 24 a so 3 2 1 0 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 Water Activity Figure 2 Full Isotherm Showing Hysteresis 11 3 THEORY AquaLab VSA 14 00 12 00 10 00 Moisture Content d b Water Activity Figure 3 Scanning Adsorption Curves From Drying to Varying aw These observations help clarify the point that an isotherm is not a single valued function The water content for any given water ac tivity value depends on the wetting and drying history of the sample It is possible to obtain isotherm data which appears to show hys teresis by failing to allow a sample to equilibrate at e
55. ge in weight of the sample This can be based on the initial weight of the test the starting weight of the stage or the minimum weight during the test Use this reference anytime you are calculat ing a percent weight 28 AquaLab VSA 5 USER INTERFACE AND MENUS Basis The VSA generates water activity values and corresponding sam ple 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 The basis parameter al lows the reporting of moisture content in two different ways percent moisture on a wet basis and percent moisture on a dry basis Percent Moisture on a Wet Basis wb g 100g total initial weight final weight pages grams of water initial weight 100 grams total Moisture Percent Moisture on a Dry Basis db g 100g solids initial weight final weight aes grams of water final weight 100 grams total Moisture For food applications moisture contents are reported on a wet basis A simple equation converts between the wet and dry basis Y moisture wet moisture dry x 100 oe y 100 moisture wet moisture dry x 100 100 moisture dry Ymoisture wet Date The VSA has an internal calendar and clock that allow it to record the time and date of each water activity reading Press Enter
56. he fan blades Fig ure 14 when cleaning the chamber a Remove any debris that may have collected within or around the sample chamber b Wrap a NEW Kimwipe around the end of the spatula thin plastic rod and moisten it with Decagon Cleaning Solution Note Do not dip a used Kimwipe into your cleaning so lution the cleaning solution can become contaminated c WASH Clean upper chamber o ring and all surfaces of the block within the o ring You may need to replace the Kimwipe if it becomes too dirty during this process 46 AquaLab VSA 6 CLEANING AND MAINTENANCE d Clean lower block with a fresh Kimwipe Be sure to clean the entire block surface e RINSE Repeat steps b through d using new Kimwipes with USP Purified water DRY Repeat steps b through d using new dry Kimwipes to help remove any moisture remaining from the cleaning Note Do not reuse Kimwipes g Visually inspect the sample chamber for cleanliness Re clean if necessary 2 Clean the Mirror a Wrap a new Kimwipe around the end of the spatula and moisten it with Decagon Cleaning Solution b WASH Swipe the moistened Kimwipe across the mir ror once A single swipe is usually sufficient to remove contaminants c RINSE Repeat steps a and b using new Kimwipes moistened with USP Purified water instead of cleaning solution d DRY Repeat steps a and b using a new dry Kimwipes to help remove any moistur
57. hod which generates dynamic isotherms By combing both methods in one instrument the VSA makes it possi ble to investigate both dynamic matrix changes due to water sorption and the kinetics of those changes This manual details VSA opera tion and provides information on the capabilities of your VSA 1 1 Customer Support If you ever need assistance with your VSA have any questions or feedback there are several ways to contact us Decagon has Cus tomer Service Representatives available to speak with you Monday through Friday between 7am and 5pm Pacific time Note If you purchased your VSA through a distributor please con tact them for assistance Email support aqualab com or sales aqualab com Phone 509 332 5601 Fax 509 332 5158 If contacting us by email or fax please include as part of your mes sage your instrument serial number your name address phone fax number and a description of your problem or question 1 INTRODUCTION AquaLab VSA 1 2 About This Manual This manual includes instructions for setting up your VSA which includes setting up an isotherm test running a test collecting data and analyzing data Please read the manual before operating the VSA to ensure your instrument performs to its full potential Decagon Devices Inc provides this manual to aid the end user in understanding the basic concepts of moisture sorption isotherms en abling them to use our instruments with confidence We ha
58. ime to make a comparison between previously saved MCC standard isotherm curves and the preloaded MCC standard curve 59 8 RUNNING A TEST AquaLab VSA 8 Running a Test 8 1 Becoming Familiar with Stages The AquaLab VSA uses test stages to maximize the utility of run ning an isotherm test In the vocabulary of setting up and running moisture sorption isotherms with the VSA an isotherm test is con sidered a collection of stages all performed on one sample Consider each stage as a unique portion of a test with its own settings while conducting all stages on one sample and combining the results into one data set at the end of the isotherm test Because each stage is unique an isotherm test could consist of one stage or up to twenty stages An example of an isotherm test with multiple stages might be running a sample through full adsorption and desorption using the static DVS method for Stage One then set ting up Stage Two to run the same test but using the DDI method on the same sample Another example would be to run a sample through full adsorption and desorption at 15 C for Stage One then in Stage Two switch the temperature to 25 C and run the same test on the same sample This stage interface makes it easy to compare dynamic and static isotherms and utilize the advantages offered by both methods all on a single sample It also makes it easy to edit currently running tests 8 2 Running a Moisture Sorption Isotherm Test
59. ing the isotherms of the two components to determine the final water activity of the mixture without actually making the product For dried products the isotherm predicts the moisture con tent of the product when it is dried to a shelf stable water activity level Finally sorption isotherms are valuable for shelf life prediction You can use the product isotherm to determine package requirements de pending on the products sensitivity to moisture or to determine the monolayer moisture content which represents the most stable state of your product The shape of the isotherm can provide information about the level of amorphous to crystalline material in a product 18 AquaLab VSA 3 THEORY Changes in the slope of the isotherm indicate phase transitions and can provide information about critical water activities for maintain ing texture properties and preventing caking and clumping You can also determine the water activity value where the glass transi tion temperature equals storage temperature or the crystallization temperature equals storage temperature 19 4 GETTING STARTED AquaLab VSA 4 Getting Started Components of VSA The VSA requires a computer and software to generate and ana lyze isotherm data You can disconnect and connect the computer once you begin a test without losing any data Your VSA ships with these items e The VSA Isotherm Generator main unit e Moisture Analysis Toolkit USB Package
60. ion tab by pressing the Menu icon Calibration is the first option highlighted in the Configuration tab Press the Enter button to bring up the Calibration screen Calibration Water Activity Weight H x 2 To offset for water activity highlight water activity press En ter and the Calibration aw screen appears Calibration a Defaults H 2 3 Highlight start and press Enter Follow the Wizard on screen commands 4 Empty the whole vial of solution into a sample cup We rec ommend using the 6 00 molal NaCl 0 76 aw Do not adjust for the offset using distilled water Ensure the rim and outside of the cup are clean Place the sample cup in the VSA sample chamber Note You may use the same verification standard to verify and adjust the linear offset 5 Carefully close the lid and move the lever to the Read position 53 7 VERIFICATION OF CALIBRATION AquaLab VSA Press the Enter button to begin testing Note If you decide at this point not to continue with the linear off set program just return the lever to the Open position or select the X to return to the previous screen 6 After your VSA finishes measuring the verification standard it displays the test value 7 Press the up and down arrows to adjust the water activity reading to its proper value for the your particular verification standard When the VSA displays the correct value press En ter to store this new value Cancel and
61. ites once obscured are now exposed to bind with water For example hydrated protein contains many sites for water binding before desorption while dehy drated protein has limited polar sites for water binding prior to adsorption 4 Some solutes may supersaturate below their crystallization wa ter activity non equilibrium condition and thus hold more water as dy declines Foods with high sugar content frequently exhibit this phenomenon Non Equilibrium If diffusion of water into adsorption or out of desorption a mate rial is slow and you do not allow sufficient time for complete diffusion then there is probably a large amount of apparent hysteresis that you can reduce by allowing sample equilibration Matrix Changes Figure 4 shows three different isotherm curves for spray dried milk powder each with unique maximum water activities and different sorption histories The moisture sorption isotherms for spray dried milk powder show a change in hysteresis due to a phase change at 0 43 aw When the isotherm ends prior to the phase change at 0 43 ay red square there is little hysteresis When the isotherm ends above the phase change blue diamond there is apparent but not actual hysteresis due to the phase change Subsequent isotherms run on 13 3 THEORY AquaLab VSA the sample after experiencing a phase transition green triangle do not show an inflection point are repeatable and exhibit only small levels o
62. lace the sample in a stainless steel sample cup that has been tared and should cover the majority of the bottom of the cup if possible The VSA is able to accurately measure a sample that does not or cannot cover the bottom the bottom of the cup For example tablets only need to be placed in the cup and not flattened or chopped to cover the bottom A larger sample surface area increases instrument efficiency by providing more stable infrared sample temperatures and enabling better water sorption 3 The VSA can accommodate samples of 500 to 5000 mg Decagon recommends sample sizes of 1000 to 1500 mg This sample size is able to give a high resolution isotherm curve without adding excessive time to the test 4 Do not overfill the sample cup Optimal results are obtained by having a thin layer of sample covering the bottom of the cup or a single layer of products such as tablets pellets or pieces Filling the sample cup can extend test time create layering within the sample and case hardening and can lead to contamination of the chamber The volume of sample vs weight of the sample has to be optimized for each material to achieve the desired resolution and test times 74 AquaLab VSA 10 SAMPLE PREPARATION 5 Do not fill the sample cup with sample while it is sitting in the chamber The sample cup should be removed from the chamber sample added and then placed back in the chamber to check the weight Make sure the rim and outside
63. les setting 0 02 a 2 RH Operating Environment 4 to 50 C 0 to 90 Relative Humidity Non Condensing AquaLab VSA 2 ABOUT THE VSA Sample Weight Range 500 to 5000 mg Temperature Control Range 15 to 60 C at STP Temperature Adjustment Increment 0 1 C Humidity Operating Range 10 to 90 non condensing Mass Resolution 0 1 mg Universal Power 110 V to 220 V AC 50 60 Hz Size Footprint 38 1 x 26 7 x 30 5 cm 15 x 10 5 x 12 in External Gas 7 PSI max if required Weight 33 pounds Sample Dish Volume 15 ml full Data Storage 1 test Data Communications USB Display 64 x 128 Graphical Case Material Machined aluminum frame polyurethane plastic with fire retardant Program Identification Alphanumeric Programmable to display Product Name Lot or Product ID Number 3 THEORY AquaLab VSA 3 Theory Water profoundly influences product attributes such as quality and safety To completely understand water relations in a product re quires 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 The nature of this relationship depends on the interaction between water and other in egredients The amount of water vapor that a product has depends on the chem ical composition
64. lighting the Defaults option in the calibration menu and pressing Enter 27 5 USER INTERFACE AND MENUS 5 USER INTERFACE AND MENUS AquaLab VSA Calibration Water Activity Weight x Volatiles The instrument gives accurate readings on most samples when the default volatiles setting is Off When reading with volatiles off the chilled mirror method is used by default However samples 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 The concentration of volatiles that causes in terference is variable and matrix dependent The most effective method to determine if volatiles are a problem is to compare dew point readings to capacitance readings If the dew point readings are more than 0 02 higher than the capacitance read ings volatiles are likely a problem and it is recommended that the volatiles setting be switched to On When you turn the volatiles set ting on the instrument only uses the capacitive relative humidity sen sor for water activities measurements and isotherm tests All other operations and features are the same including measurement times and adjusting for linear offset Press Enter to toggle the volatiles setting on and off Weight Reference Weight reference is the reference used when calculating the percent chan
65. lone instrument a computer must be attached to download test results The Moisture Analysis Toolkit software makes it easy to download moisture sorp tion 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 After installing the Moisture Analysis on a computer follow these steps to utilize the software Connect 1 Connect your USB cable between the VSA COM port and the USB port on your computer 2 Open the Moisture Analysis Toolkit software 3 Select the proper COM port in the toolbar 4 Click the Connect button in the toolbar 9 1 Configure and Start a New Test 1 Once you connect the VSA click the Wizard button in the toolbar 2 Follow the Wizard instructions and fill in the parameters of your test and each stage desired 3 After completing the Wizard follow the instructions displayed on the VSA to start your test 9 2 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 1 Connect to VSA running test 2 Click the Wizard button in the toolbar 72 AquaLab VSA 9 MOISTURE ANALYSIS 3 Modify stages in the currently running test 4 Click Next 5 Click Finish and Allow the Wizard to finish communicating with the device 9
66. mponents VSA Configuration Tab Customer Support Data Tab Declaration of Conformity Desiccant Cartridge Replacement Desorption Diagnostics Dynamic Dew Point Isotherm DDN Dynamic Vapor Sorption DVS Email Equilibrium Isotherms p External Gas 6 Flow Rate Air Fuse Glass Transition Humidity Operating Range Hysteresis Isotherm Models Moisture Sorption Types Isotherm Tab Linear Offset Matrix Changes Measurement Tab Microcrystalline Cellulose MCC Moisture Analysis Toolkit Moisture Content Basis Moisture Sorption Isotherm Moisture Sorption Test Power Outage Product Development Salt Standard Sample Prep Coated and Dried Seller s Liability Setup Instrument Shelf Life Prediction Specifications 6 Stages Standards Static Isotherms Tabs Tare Temperature 100 AquaLab VSA INDEX Adjustment Increment Temperature Control Range Test Wizard Theory Trigger Troubleshooting User Interface Vapor Equilibrium Verification Standards Volatiles Warranty Water Activity Accuracy 6 Range 6 Repeatability Resolution 6 Testing Water Tank Weight Reference Working Isotherm 101
67. nlock all of them at once For example if you do not want an individual changing the instrument measure ment temperature the administrator can lock that function for that individual Administrators can lock the calibration temperature temperature equilibration sensor selection mode date time region password auto save number of beeps contrast and delete functions User Setup Users can be added edited or deleted from this screen To add a user press the Enter button with the New highlighted To edit or delete a user choose the target user and press Enter When creating a new user an alphabet screen appears where you can enter a name using lower case upper case and accents User Jean Paul Sarah Hew tl 32 AquaLab VSA 5 USER INTERFACE AND MENUS He o 7M eo TT Po 2 oo oo 0 L A m OCE ES w Fl L ll T oo e oF coll wa ao hj oo fre oot FE ee Note User setup is not required for instrument operation It is avail able for users wanting to be compliant with 21 CFR Part 11 or who want to maintain the settings they have selected oe Auto Restart Auto restart enables 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 We recommend this be set to on to prevent data loss Note Restart tests with a new sample if power outages lasts more than 80 minutes Lighting
68. nt to the bottle lip located in the lid with water as shown in Figure Figure 12 Desiccant Lid Secure the lid to the desiccant cartridge Verify the lid seal is correct by using the empty squeeze bottle included with your VSA Refer to Figure 13 Check ing Desiccant Cartridge for Leaks i Have a pan or cup with about one inch deep water in the bottom 42 AquaLab VSA 6 CLEANING AND MAINTENANCE ii Hold one finger over the output fitting ili Pressurize the desiccant tube using the pressure bot tle as shown in the figure 13 Note the bottle just needs to be squeezed with air in it do not put water into the squeeze bottle v Place the desiccant tube with the lid into the water If the lid is not sealed the water could flow into the desiccant cartridge Hold the tube in the water only as long as needed to verify the test v Look for bubbles escaping from the lid A large num ber of bubbles indicates the lid is not sealed You must remove the lid and reset the washer Lubricate the washer with water and put the lid back k When you place the desiccant cartridge into the desiccant receiver you should wet the o rings on the fittings for ease of installation and to reduce wear Be sure to align the black fitting with the black ringed hole before insertion to ensure a proper seal AquaLab uses a 10 to 20 mesh indicating drierite as the desiccant Indicating drierite is not required by the size of a replacem
69. of the sample cup are clean Wipe any excess material from the cup with a clean Kimwipe Material left on the rim or outside of the sample cup can contaminate the chamber and potentially interfere with the scale 10 2 Sample Needing Special Preparation Some samples require additional preparation to ensure accurate read ings To find out whether special sample preparation methods are necessary multiple water activity readings should be taken to see if readings stabilize water activity and time Coated and Dried Samples Samples with high sugar or fat coatings often take a long time to equilibrate If this is the case for your samples it is not a problem with the instrument it simply means your samples take longer than most to equilibrate To reduce the time needed to test the samples you can crush or slice the sample prior to sampling This increases the surface area of the sample thus decreasing reading times How ever if the effectiveness of the coating is being tested the samples should remain unchanged Also modifying some samples can alter the water activity readings and start point of your isotherm Slow Water Emitting Samples Some extremely dry dehydrated highly viscous water in oil but ter high fat or glassy compositions have slow water emitting prop erties Tests with these materials may take longer than with other types of materials Decagon recommends running the test as a DVS rather than DDI to ensure equilibri
70. open a new window Cycle to the desired trigger value using the up and down arrows The trigger can be shut off or be any value be tween 0 001 and 1 hr The trigger value represents an accept able change in mass per change in time to indicate equilibrium for a given step Next choose the number of readings or events meeting the trigger value that are required to achieve equilibration For ex ample choosing 3 means that in order for a step to have reached 66 AquaLab VSA 8 RUNNING A TEST equilibrium three dm dt readings in row must be less than the set trigger value You can choose any value between 1 to 10 Setting a higher trigger value and a lower number of events makes the test faster but may not result in complete equilib rium We recommend 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 Trigger Readings dime dt 3 O 020 hr al x 5 To choose to include a timeout setting highlight Timeout press the Enter button 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 maximum time allotted for each ay step not the time from starting ay to final aw The default value is off which means there is no timeout v
71. p to 0 90 ay You can run AquaLab VSA 3 THEORY icing E Creme Filling ACake Wood Pulp x Granola Bar Milk Powder Moisture Content d b 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 Water Activity Figure 1 Moisture Adsorption Isotherms the range of a by controlling water activity levels using saturated salt slurries or mechanical humidifiers and determining equilibrium moisture content at each water activity level Equilibrium is assumed when the weight of the sample stops changing This process is of ten accomplished using sealed chambers such as desiccators and the equilibration process can take weeks There are several additional challenges to executing this manual method Tracking the weight of the samples can be difficult Also when removing the samples for weighing you potentially expose them to ambient humidity and at high humidities there is the possibility of mold growth The Decagon VSA Isotherm Generator uses the DVS method described above to speed up and automate the construction of equilibrium isotherms eliminating the challenges of manual determination In additional to equilibrium moisture contents at a given water activity equilibrium isotherms provide information about kinetics of sorption and water vapor diffusion properties Moisture sorption isotherms can also be determined using dynamic methods such as the DDI method used by the VSA The DDI method 3 TH
72. r activity of 0 03 to 0 1 ay final water activity gt 0 80 aw flow rate of 80 to 100 ml min resolution of 0 01 a and no timeout should be used 8 4 Creating a Working isotherm Using the VSA Users can generate working isotherms using the VSA as described in the Theory section of Section 3 though it requires several steps 1 Isotherm Tests Generate two isotherm tests using the VSA one for adsorption and one for desorption with both starting at the current water activity value A working isotherm is an analysis of the sorption characteristics of a sample starting from its native state Generating this data requires the analysis of two sub samples in the same condition as the original sample Adsorption Curve Analyze one sub sample for adsorption from its current state Set up one stage of the test with your desired settings for method DDI or DVS temperature step value flow rate etc but the starting water activity must be current and the final water activity must be a value higher than the current water activity of the sample 68 AquaLab VSA 8 RUNNING A TEST 3 Desorption Curve Analyze a second sub sample for desorp tion from its current state The test is again setup with one stage with desired settings for method DDI or DVS temper ature step value flow rate etc but the starting water activity must be current and the final water activity must be a value lower than the current
73. results in desorption while selecting a final a higher than the starting aw results in adsorption Press the Save button when finished 3 To choose the temperature of the stage highlight Tempera ture press the Enter button and then cycle to the desired temperature using the up and down arrow keys hold down arrows for accelerated scrolling You can choose any temper ature between 10 and 60 C and run each stage at a unique temperature 4 To choose the desired ay resolution highlight Resolution press the Enter button and then cycle to the desired value using the up and down arrows You can choose any value be tween 0 003 and 1 0 aw The resolution for DDI determines the target a resolution Setting a higher step value makes the test faster but decreases the aw resolution Decagon recommends a DDI step of 0 01 ay stage 1 solution 0 010 an Flow 100 mL min Timeout OFF Loop On tlr S e 5 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 You can select any value between 10 and 163 ml min Higher flow rates speed up the test but may result in lower data resolution and non equilibrium conditions The default value of 100 ml min is suitable for most products 6 To choose to include a timeout setting press the Enter but ton with Timeout highlighted and then cycle to the desired 64 AquaLab V
74. roperties 4 Optimize moisture contents at a safe water activity that max imizes moisture and avoids over drying 5 Determine shelf life and storage stability of a product 6 Predict packaging requirements based on sorption properties of a product 7 Determine kinetics of sorption and water vapor diffusion coef ficients 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 AquaLab VSA 2 ABOUT THE VSA 12 Determine the relationship between water activity and glass transition temperature 13 Determine the relationship between water activity and crystal lization 14 Determine hysteresis levels for a product 15 Determine the moisture sensitivity of a product 16 Determine the equilibrium moisture content at a given water activity 17 Allow rapid moisture content determination from water activ ity analysis through an isotherm curve 2 2 Measurement Method The VSA is the only automatic isotherm generator that can create isotherms using both dynamic and static methods The VSA uses the Dynamic Dew Point Isotherm DDI method to produce dynamic isotherms and a controlled humidity and balance system commonly referred to as Dynamic Vapor Sorption DVS to produce static or equilibrium isotherms The DDI method for d
75. rtridges are hard to install Poor temperature control on the system Problem 10 Problem 11 Problem 12 Problem 13 Problem 14 Problem 15 Problem 16 Problem 17 Problem 18 Problem 19 Problem 20 Problem 21 Problem 22 Problem 23 Problem 24 Problem 25 Problem 26 Problem 27 Problem 28 78 AquaLab VSA 11 TROUBLESHOOTING 1 PROBLEM VSA does not turn on SOLUTIONS 1 Check to make sure your power cord is securely attached to the back of the instrument and it is plugged into the power outlet 2 A power surge may have caused a fuse to blow To change the fuses follow these instructions a b Unplug the power cord Locate the panel where the power cord plugs in The fuse box is on the right side of that panel Press in on the release tab and pull the fuse holder out Pull the broken fuse s out and replace with a 1 25 Amp 250 V fuse Caution Do not use any other kind of fuse or you risk damaging your instrument and voiding your warranty Replace the fuse holder and push it into the fuse well until the release tab snaps in place Connect the power cord and turn your instrument on If the fuse blows again a failed component may be causing the problem Contact Decagon to make arrangements for repairs 2 PROBLEM Readings are slow or inconsistent SOLUTIONS 1 The sample chamber may be dirty Refer to Section 6 for di rections on cleaning the sample chamber
76. s of the desiccant tubes Initially when the diagnostic screen is turned on the pump supplies flow through the active desiccant tube to help 92 AquaLab VSA 11 TROUBLESHOOTING verify that it can desiccate properly After 30 seconds of pumping the desiccant humidity reading should be 5 or less If the desic cant humidity is unable to reach 5 humidity refer to Section 6 for instructions on replacing the desiccant tubes Weight Cal The weight calibration saved a scalar into memory that applies to all subsequent weight readings A scalar of 1 means that the weight has not been changed from the default factory cali bration If the scalar strays too far from 1 you may need to reverify the balance and also certify the weight standard again Dew Offset The chilled mirror dew point calibration offset is zero if it is running off of the default factory calibration This value indi cates the offset the instrument applies to the water activity readings for accurate readings Diagnostics Cap Offset 0 0015 aw ae at Cap Offset The capacitive RH calibration offset is zero if the VSA is running off of the default factory calibration This value indicates the offset the instrument applies to the water activity readings for accurate readings a 93 12 SUPPORT AND REPAIR AquaLab VSA 12 Support and Repair Note If you purchased your AquaLab from one of our international distributors please contact them They c
77. s on cleaning 2 The chamber mirror may be dirty Refer to Section 6 for di rections on cleaning 4 PROBLEM Warning screen displays a message that the sample is too hot 80 AquaLab VSA 11 TROUBLESHOOTING Warning Remove sample Sample is too hot x AT 7 26 C Dew o 02 EJ SOLUTION Your sample temperature is too high for the instrument to equili brate with it in a reasonable amount of time The instrument and sample need to be in temperature equilibrium to take accurate mea surements Therefore very cold samples take a long time to measure for the same reason To avoid this problem make sure to only mea sure samples that are at the same temperature as the instrument 5 PROBLEM Message on screen displays aw below instrument detection limits Heasurement 4 13PM lt 0 0791 dw a 24 41 C Dew 1 31 EJ SOLUTIONS 1 The sample is too dry for the instrument to read accurately If your sample has a water activity that is below the detection limits of the instrument this message comes up Essentially it means that there is not enough sample moisture to condense on the mirror and provide a reading 2 Or the mirror may be dirty Try cleaning the mirror and cham ber and measuring the sample again 81 11 TROUBLESHOOTING AquaLab VSA 6 PROBLEM Message on screen displaying dew point sensor failure Error Dew point sensor failure SOLUTION The cooler is damaged and needs to be servi
78. snap on housing that you 23 4 GETTING STARTED AquaLab VSA i Water fill plug Water tank fill extension Water tank drain plug Fan filter Figure 9 Tank Fill Extension can easily remove 9 Use the water tank drain plug to remove the water from the water tank Note Have a receptical ready to catch the water flow 24 AquaLab VSA 5 USER INTERFACE AND MENUS 5 User Interface and Menus The AquaLab VSA is a stand alone 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 These tabs indicate the four menus you can access To change between the tabs press the right most button below the Menu icon The Enter icon is the Read or Enter button 5 1 Isotherm Tab The Isotherm tab is the main screen and displays each time you turn on your VSA If the Isotherm tab screen does not appear re fer to Section 11 for troubleshooting Operators can initiate a new test from this screen by pressing the wizard icon third button from right If a test is already running this screen displays the latest test values including water activity weight or moisture content and temperature Pressing the second button activates the chart view MCC 2 47PM 0 103 dw 1545 4 mg 275 07 C 2 43 26 28 he 5 2 Measurement Tab The Measurement tab allows you to take water activit
79. surement error you may access a screen that displays values for component performance Navigate to the Configuration tab and then scroll down to the Diagnostics op tion Press Enter to open a list of components and their values 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 C Typical ranges for the lid base and sam ple temperatures are between 24 5 and 25 5 C when unit tempera ture is set to 25 C If the mirror temperature is at lid temperature the cooler has failed and must be replaced If the mirror is below the lid temperature or appears to be random the thermocouple wire is broken and must be repaired If the lid temperature is much higher than the set temper ature the lid fan may have failed and must be replaced Diagnostics RH fora 22733 Weight 1565 6 mg Optical SOG iy Latch Closed f aE a 1C RH This screen shows the capacitive sensor RH percentage which should always be between 0 and 100 Weight The weight measurement updates in real time and can be zeroed for measurements by pressing the scale icon 2nd button from the left If the weight reads overload or underload the balance is broken and needs to be replaced A negative value indicates that the balance needs to be re zeroed if you want to take weight mea 91 11
80. th Stages 8 2 Running a Moisture Sorption Isotherm Test For the DDI method 20 21 25 25 25 26 37 41 41 44 46 49 49 50 5l 58 iii CONTENTS AquaLab VSA For the DVS Method 65 8 3 Using DDI to investigate Glass Transition 68 8 4 Creating a Working isotherm Using the VSAJ 68 8 5 Editing a Running Isotherm Test 69 8 6 Running a Water Activity Test 0 70 9 Moisture Analysis 72 9 1 Configure and Start a New Test 2 72 9 2 Modify a Currently Running Test 2 72 9 3 Download and Export 0 73 10 Sample Preparation 74 10 1 Preparing the Sample 2 74 10 2 Sample Needing Special Preparation 75 11 Troubleshooting 77 11 1 Diagnostics Screen 2 2 20 00 91 12 Support and Repair 94 12 1 Repair Costs 0 2 2 22 00 0008 95 13 Appendix A 96 14 Appendix B 97 15 Declaration of Conformity 98 16 Certificate of Traceability 99 V AquaLab VSA 1 INTRODUCTION 1 Introduction The AquaLab Vapor Sorption Analyzer VSA is an automatic isotherm generator from the world leaders in water activity measurement The VSA is the only automatic isotherm generator that can generate isotherms using both the Dynamic Vapor Sorption DVS method which generates equilibrium isotherms and the Dynamic Dew Point Isotherm DDI met
81. ual for options SOLUTION The firmware on the instrument is corrupted and needs to be reloaded Contact your Decagon representative for further options 11 PROBLEM Message on the screen displays a missing bootstrap loader error SOLUTION The instrument cannot download new firmware updates To down load new firmware to the VSA or to stop this message from display ing the instrument must be serviced by Decagon 12 PROBLEM Message on the screen displays an annual calibration reminder This unit is due for annual calibration Please contact Decagon Remind Me Later Don t display again 84 AquaLab VSA 11 TROUBLESHOOTING SOLUTION This message indicates that it has been at least one year since your instrument has been calibrated and serviced by Decagon or your lo cal distributor Decagon service personnel recommended that you return your instrument so that we can help you ensure that you are getting the most accurate readings possible from your VSA Click remind me later to be reminded in a couple of weeks click do not display again if you do not want the device to remind you in the near future 13 PROBLEM Message on screen displays no equilibration points available Test 23 MCC 1 7 59AM Ho equilibration points available 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
82. um 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 75 10 SAMPLE PREPARATION AquaLab VSA runs Glass beads can be helpful in some instances Volatile Samples Samples with certain volatiles in high enough concentrations may give inaccurate water activity values when using the chilled mirror This is because the volatiles condense on the mirror during the read ing process but do not evaporate from the mirror as water does As a result the reading on samples with volatiles may not be accurate The concentration of volatiles that causes interference is variable and matrix dependent The most effective method to determine if volatiles are a problem is to take water activity readings and com pare results from the chilled mirror and capacitance sensor Refer to section 5 for how to take water activity readings and switching between sensors If the dewpoint readings are more than 0 02 higher than the capacitance readings volatiles are likely a problem and should be read with volatiles turned to on Decagon designed the VSA for measuring volatiles such as propylene glycol ethanol and acetic acid The VSA contains both the chilled mirror dewpoint and a capacitance sensor After measuring a sample with volatiles with the capacitance sensor it is a good idea to cle
83. ve made every effort to ensure the content of this manual is correct and sci entifically sound 1 3 Warranty The VSA has a one year warranty on parts and labor Your warranty automatically validates upon receipt of the instrument We contact you within the first 90 days of your purchase to see how the VSA is working for you 1 4 Seller s Liability Seller warrants new equipment of its own manufacture against defec tive workmanship and materials for a period of three years from the date of receipt of equipment Note We do not consider the results of ordinary wear and tear neglect misuse accident and excessive deterioration due to corro sion from any cause as defects The Seller s liability for defective parts shall in no event exceed the furnishing of replacement parts Freight On Board the factory where originally manufactured Material and equipment covered hereby which is not manufactured by Seller shall be covered only by the warranty of its manufacturer Seller shall not be liable to Buyer for loss damage or injuries to persons including death or to property or things of whatsoever kind including but not without limitation AquaLab VSA 1 INTRODUCTION loss of anticipated profits occasioned by or arising out of the instal lation operation use misuse nonuse repair or replacement of said material and equipment or out of the use of any method or process for which the same may be employed The use of this
84. ves from the desorption curve to the adsorption curve You can observe this transition re gion at any point on the isotherm if you change the direction of the sorption and the product exhibits hysteresis Figure 5 N oO fF aA QO N CO O ans s kej x e g c e S g Z 2 e 0 4 0 6 Water Activity Figure 5 Working and Full Isotherm for Wood Pulp Note Please refer to Section 8 4 for information about running a working isotherm using the VSA 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 thermody namic functions of water in foods The models are necessary when us ing isotherm methods with low data resolution to interpolate between isotherm data points While there are 270 proposed isotherm models the most commonly used models are the Guggenheim Andersen de Boer GAB and Brunauer Emmett Teller BET Since the BET model is only applicable up to 0 50 aw the GAB model is widely 16 AquaLab VSA 3 THEORY accepted as the most useful for characterizing isotherms across the entire water activity range Its coefficients also have theoretical phys ical meaning such as providing monolayer moisture content A new empirical model called the Double Log Polynomial DLP or Chi plot has proven to be even better than
85. water 17 3 THEORY AquaLab VSA activity An additional function of the isotherm is moisture content predic tion Although water activity is a much better predictor of safety and quality than moisture content there are times when it is neces sary to know both water activity and moisture content as well as the relationship between the two parameters for a given product Wa ter content measurements can be inaccurate time consuming and require a precision balance As an alternative to moisture content measurement methods you can use the sorption isotherm to deter mine moisture content based on water activity usually with better precision than actually running a moisture content analysis and in much less time Customers can utilize isotherms to determine the effect of temper ature on water activity and moisture content readings Isotherms conducted at several different temperatures show the temperature at which a product in a sealed package at constant moisture content is at unstable water activity levels Isotherms can be very valuable for formulation and product devel opment By comparing the isotherms of different formulations it is possible to determine if a product can be adjusted to allow higher moisture content at a given water activity or a lower water activity at a given moisture content The result can be a moister product that is still shelf stable For those producing multi component products it is possible us
86. water activity of the sample 8 5 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 1 Press the Wizard icon as you did when starting a test The Configure Test screen appears Configure Test ame MCC Initial MC Hone End Test 1L lt lt H 3 2 Press the double right arrow to edit the selected test The Configure Stages screen appears Configure Stages End Current Stage 1 001 Current 0 700 a SBS 0OVS 0 700 40 300 a Hew gI w E 3 The current running stage spinner icon and completed stages lock icons cannot be edited Add additional stages by se 1L 69 8 RUNNING A TEST AquaLab VSA lecting New and pressing the Enter button Then setup each stage as outlined above To edit an existing stage that is not currently running and is not complete select it and press the Enter button Adjust the settings as instructed above Note If you do not want to end the current stage make sure there is not a Check Mark next to End Current Stage 4 To alter a currently running stage insert a new stage after the currently running stage Make sure to set the starting ay to current if you want the new stage to resume where the previous stage left off Then sel
87. y 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 25 5 USER INTERFACE AND MENUS AquaLab VSA Measurement 4 13PM 0 764 dw Pa 24 16 C Dew 1 31 x Heasurement 4 05PM AT 0 08 C Dew o 00 E 5 3 Configuration Tab The Configuration tab allows the operator to view various configu ration options Pressing the up and down arrows moves through the configuration options while pressing the right and left arrows allow the operator to page through the options Configuration 10 23AM Calibration Volatiles Mo mt Ref Initial wt Basis Hwb g100g total 4 FF i 26 AquaLab VSA CO Configuration 10 23AM Date Sep 26 2011 Time 10 23AM Ay Settings Regional Formatting H E m Configuration 10 32AM Admin Settings Auto Restart On Lighting On External Gas OFF Thr H Configuration 10 33AM Contrast Diagnostics About Thar H Highlight Calibration and press the Enter button to open the Cal ibration menu where you can make either a water activity or weight For more details on weight and water activity calibration procedures refer to Section Verification of Calibration You may also reset the calibration to the factory defaults by high
88. ynamic isotherms is a water activity and gravi metric analysis method that controls neither water content nor water activity but dries or wets the sample and measures water activity and water content during the wetting or drying process The VSA deter mines water content by weighing the sample using a high precision magnetic force balance and water activity with Decagon 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 The VSA water reservoir mounts to the temperature controlled lower block to ensure humidity saturation and minimize temperature fluctuation The DVS method for static or equilibrium isotherms consists of track ing sample weight change as the sample is exposed to different con trolled humidities The sample is held at each humidity for a preset time interval or until a steady state weight change is achieved the goal being to achieve equilibrium between the sample water activ 2 ABOUT THE VSA AquaLab VSA ity and the controlled humidity Customers typically choose several humidity levels to preset during the set up process The instrument then tracks equilibrium progress at each humidity level and auto matically steps to the next humidity when equilibrium requirements are achieved Weight change versus time data is recor
89. your VSA clean ing kit from the Measurement Tab This cleans the air inside the chamber helping it come back to a stable sampling environment It is important to verify VSA water activity calibration against known standards to guarantee optimal performance and accuracy AquaLab recommends verification before running a new isotherm test 7 1 Water Activity Verification 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 as described in Section 5 the VSA performs water activity verification on the capacitance sensor only If you set volatiles to no the VSA verifies the dew point sensor While the instrument does not require a routine full calibration it is important to verify for linear offset periodically The components used by the instrument to measure water activity are subject to contamination which may affect VSA performance When this occurs it changes the accuracy of the instrument This is what is called a linear off set Therefore frequent verification assures the VSA is performing cor rectly You can check linear offset by using two different verification standards 49 7 VERIFICATION OF CALIBRATION AquaLab VSA 7 2 Verification Standards Decagon s verification standards are specially prepared unsaturated salt solutions that have a specific molality and water activity value which are accurately measur

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