Computrac MAX-1000 User's Manual - Arizona Instrument

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10 PERFORMANCE ENHANCEMENT10.1 INTRODUCTION10.1.1 The MAX loss-on-drying moisture analysis system takes advantage of computertechnology to reduce test times and increase precision over standard vacuum ovenor convection oven drying procedures. The sample is added to an aluminumsample pan sitting atop an electronic force balance within a test chamber. As thesample heats and loses weight due to moisture evaporation, the balance recordsthat weight loss and transmits the data to the microprocessor. The microprocessorinterprets the information and compares the sample's weight loss to a standarddrying curve. The final moisture concentration is extrapolated from the curve andresults are available within minutes.10.1.2 A typical drying curve (see Figure 53 below) consists of three portions: The firstportion (A-B) represents the sample's weight loss as it heats from room to testingtemperature.10.1.3 Section B-C is linear, representing moisture loss from the interior of each particleof the tested sample. The final portion of the curve (C-D) is exponential in natureand represents the final evolution of moisture from within the particle. The pointat which no additional weight loss occurs represents the complete evolution ofwater from the original sample (E).Figure 53 DRYING CURVE48
10.1.4 The final portion of the curve (D-E) is the longest and most time-consumingportion of the entire testing process. The time for a sample to reach zero residualmoisture can take from one to 24 hours depending upon the sample, samplepreparation, and testing temperature. The MAX-1000 loss-on-drying systemcalculates the sample's moisture concentration through mathematical extrapolationfrom the exponential (C-D) portion of the curve.10.1.5 Normally, 1 gram to 10 grams of sample are placed on an aluminum sample pan inthe test chamber. (Range can be 150 milligrams to 40 grams.) The aluminum pansits on a pan support coupled to a sensitive digital electronic force balance. Theforce balance registers the initial weight of the sample before testing and relays thesample's decreasing weight to the microprocessor for evaluation. Balance readingsare averaged to eliminate signal interference or erroneous data.10.1.6 Test temperatures can be programmed between ambient (25°C) and 225°C ineither a one or two-step temperature contour. Heating is done through a 700-wattnichrome element, which is located on the underside of the test chamber's lid. AnRTD monitors the temperature of the test chamber and sends that informationback to the microprocessor. Under the microprocessor's control, the heaterelement is cycled on and off to bring the test chamber to the programmed level.The temperature is maintained within 1°C of the programmed temperaturethroughout the test.10.1.7 A unique HISTART mode (see HISTART TEMPERATURE) on the MAX-1000takes advantage of the evaporative cooling effect at higher temperatures to reducetest times and improve repeatability. When the HISTART mode is used, eachcycle begins with a higher temperature setting to rapidly evaporate moisture fromthe sample. The cooling effect of surface evaporation prevents burning of thesample although the chamber temperature may be quite high. During this hightemperature period, the sample's weight loss is closely monitored to detect whenthe evaporation rate has decreased to a point where the cooling effect is lost. Toprevent sample burning, the unit drops the temperature to the lower setting forslower drying. The higher beginning test temperature speeds the sample throughthe A-C portion of the drying curve. The lower ending temperature takes thesample through the exponential portion (C-D) of the curve where an accurateprediction of the moisture concentration can be made. See the section onHISTART TEMPERATURE page 54, for procedures on determining the idealtemperatures. Page 27 gives information on programming these values into theMAX-1000.49
Page 1:
USER MANUALCOMPUTRAC ® MAX ® 1000
Page 5 and 6:
PACKING and SHIPPING INSTRUCTIONSTh
Page 7 and 8:
Figure 1 MAX-1000 PACKING DIAGRAMvi
Page 9 and 10: TABLE of CONTENTSPACKING and SHIPPI
Page 11 and 12: 12 PERFORMANCE VERIFICATION .......
Page 13 and 14: 1 INTRODUCTIONThe Arizona Instrumen
Page 15 and 16: Location SelectionSelect a location
Page 17 and 18: 2.3.2 Obtain a sample of test mater
Page 19 and 20: 3.4 CONTROLS3.4.1 The front panel c
Page 21 and 22: 3.6.4 After “START” has been pr
Page 23 and 24: 4.1 INSTALLATION OF BALANCE PAN SUP
Page 25 and 26: 4.2 AC POWER CONNECTIONFigure 7 MAX
Page 27 and 28: 4.5 NITROGEN PURGE SETUP4.5.1 Some
Page 29 and 30: 4.7.4 Connect tubing from the conne
Page 31 and 32: 4.10 ENABLE PRINTER OUTPUT4.10.1 Wi
Page 33 and 34: 5 MENU SYSTEM: INSTRUMENT CONFIGURA
Page 35 and 36: 6 “MEMRY” KEY: MEMORY START SEL
Page 37 and 38: 7.1.1 To select a menu item, move t
Page 39 and 40: Test TemperatureThe current setpoin
Page 41 and 42: Start Temp ControlThe START TEMP CO
Page 43 and 44: Some samples contain more than one
Page 45 and 46: The PAN TARE OPTIONS offers the use
Page 47 and 48: ! RESULT DISPLAY OPTIONSTest result
Page 49 and 50: 7.4 CALIBRATION MENU7.4.1 CALIBRATE
Page 51 and 52: connected (IBM or Epson). Select th
Page 53 and 54: tags entered by the operator to ide
Page 55 and 56: ! SYRINGE TESTThis function is usef
Page 57 and 58: 8 “PARAM” KEY: TEMPORARILY CHAN
Page 59: 9 MISCELLANEOUS MENU MESSAGES9.1 CO
Page 63 and 64: Figure 54 MOISTURE VS. TEMPERATURE
Page 65 and 66: 11.2.2 The sample should be added e
Page 67 and 68: 12 PERFORMANCE VERIFICATIONPeriodic
Page 69 and 70: eliable results, use a high quality
Page 71 and 72: 13 ROUTINE MAINTENANCEThe MAX-1000
Page 73 and 74: 13.3 SAMPLE PAN SUPPORTThe sample p
Page 75 and 76: SYMPTOM DIAGNOSIS REMEDYNo power to
Page 77 and 78: TEMPERATURE CIRCUITProbable cause:A
Page 79 and 80: FeatureSpecificationTest DisplayInt
Page 81 and 82: 18 APPENDIX A18.1 PARAMETER DEVELOP
Page 83 and 84: PARAMETER DOCUMENTATION:To ensure o
Page 85 and 86: If smaller standard deviations are
Page 87 and 88: 21 MAINTENANCE CONTRACTArizona Inst
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Computrac MAX-1000 User's Manual - Arizona Instrument

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