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Marconi TF 933C Instruction Manual

Moisture meter
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M.I. 2.5c
6/83/M
Instruction Manual
No. EB 933C
for
Moisture Meter
TF 933C
1972
MARCONI INSTRUMENTS LIMITED
ST. ALBANS HERTFORDSHIRE ENGLAND
EB 933e
2g - 1/83

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  • Page 1 Instruction Manual No. EB 933C Moisture Meter TF 933C 1972 MARCONI INSTRUMENTS LIMITED ST. ALBANS HERTFORDSHIRE ENGLAND EB 933e M.I. 2.5c 2g - 1/83 6/83/M...

  • Page 2: Table Of Contents

    Contents Chapter 1 GENERAL INFORMATION 1.1 Features 1.2 Data summary 1.3 Accessories Chapter 2 OPERATION Installation 2.2 Controls and connections 2.3 Preparation of sample 2.4 Loading the compression cell 2.5 Reading the instrument Avoiding errors Chapter 3 TECHNICAL DESCRIPTION 3.1 Circuit description Chapter4 MAINTENANCE 4.

  • Page 3: Chapter 1 General Information

    Chapter General information 1.1 FEATURES The moisture meter measures the "jointure content of a wide range of hygroscopic materials, particularly those ol' origin, in the field or laboratory. The test cell which is of the compression type stowed in the instrument when not in use.

  • Page 4: Data Summary

    1.2 DATA SUMMARY Moisture contents from below air-dry to near RANGE: satu ration. The basic accuracy of the instrument is ACCURACY: 10.5%, m. c. , but variations duc to the nature of the samples may reduce this to m. c. The accuracy tends to fall at high moistu re contents.

  • Page 5: Accessories

    One 4 BA hexagonal wrench, Marconi type 22951-006; for carrying out the standardization test detailed in Sect, 4.2. One Instruction Manual No. EB 933C.
  • Page 6 Content Fig. 1.2 The moisture meter showing accessories Accessories available Standard Calibration Data: Cereal grains and agricultural seeds TM 4473A/1 TM 4473A/2 Flour and wheat Cigarette tobacco TM 4473A/3 Tick beans TM 4473A/8 Polished rice and paddy TM 4473A/9 TM 4473A/10 Paper Special Calibration Data;...
  • Page 7 Small grinder; for grinding whole grain etc. Spare Standard Electrode "I'M 4178A; lor eojnpression cell Large Electrode Unit TM 4178A/.'I (contplete Ring TC and I 'lunger TC 22433/2); ror use with compression cell elect rode to la rge The unit has a (lia tneter ol' Inches and holds about 10 samples.

  • Page 8: Chapter 2 Operation

    Chapter Operation 2.1 INSTALLATION The performance of this instrument may be impaired by lengthy NOTE exposure to a damp atmosphere. Drying for a short period in a warm dry atmosphere will restore it to give normal performance. Ensure that the instrument is switched OFF before connecting any leads and only switched on when actually taking measurements, hence prolonging the life of the batteries.

  • Page 9: Preparation Of Sample

    will' the Ensure that compression cell electrode using the lead provided. into larger plugs goes to the main instrument and do not attempt to Thore is no significance in smaller sockets on the compression cell. of the individual leads as there is no polarity to observe and the connect ionn reversed without effect.
  • Page 10 Unscrew the clamp. Withdraw the test cell. Take out the plunger, See that the insulat ing ring is well seated on the electrode with its open upua rds. Tn handling the electrode, hold by the edges. Do not handle the upper surface as this may deposit moisture on the insulating surface between the two electrode rings.

  • Page 11: Reading The Instrument

    Sheets and boards (e.g. cardboard) Thin those The ring and plunger of the test cell are not required for for the sheets should be folded to give a thickness of about 0.25 large test cell. Fig. 2.2 Use of compression cell with thin sheet materials Put the sheet to be Place the electrode in position on the base of the clamp.
  • Page 12 NOTE : The 'tens' dial (left-hand BALANCE knob) should not be on the 0 or positions when setting zero. As these are the most sensitive ranges, traces of leakage due to atmospheric humidity and effect of electro— static induction may cause the reading to be a little unsteady. Switch to any range other than 0 or I to set zero.

  • Page 13: Avoiding Errors

    4 SLIDING RED SCALE SHOWS scm.r MOISTURE CONTENT (120 y.) ROOM UMPERATURE GROUNO Content Moisture Batance 3 DIAL READING (2248) OlAU6 TRANSFERED TO FIXED BLACK SCALE Fig. 2.3 Sequence of reading moisture content 2.6 AVOIDING ERRORS Sampling errors If several samples are tested from a st-oeK ol' tn:tterial the readings generally will vary a little.
  • Page 14 If this degree of error is not acceptable it may be possible to save time by gently heating up the test cell to match the temperature of the grain. Total inaccuracy Temperature difference between cell and sample. o c moisture content 1.0% 1.6% 2.1%...

  • Page 15: Chapter 3 Technical Description

    Chapter Technical description 3.1 CIRCUIT DESCRIPTION The electrical measuring circuit, as shown in Fig. 7.1, consists o! a Wheatstone bridge in which the specimen forms one arm and the two calibrated moisture controls form the ratio arms. The out-of-balance voltage is applied to the inputs of a FET differential amplifier and displayed on a centre zero meter.

  • Page 16: Chapter4 Maintenance

    Chapter Maintenance 4.1 INTRODUCTION This chapter contains information for keeping the equipment in good working In case ol' trouble or for advice on order and for checking the overall performance. servicing this instrument, please write or telephone your nearest representative, whose name and address can be found on the label affixed to the inside front cover of the instrument.

  • Page 17: Cleaning

    'flush' setting. 4.5 ACCESS AND LAYOUT The diagram Fig. 4.1 illustrates the accessibility of the components of the Moisture Meter TF 933C. Access to the replaceable dry batteries is explained in section 4.6. 9.3.'W (1)
  • Page 18 CARRYING 9V CELLS COVER CALIBRATION SOCKETS RELEASE MECHANISM ELECTRODE LEAD SOCKETS STOWAGE COMPARTMENT COMPRESSION CELL ASSEMBLV Access and layout fi g. 4.1 933C (1)

  • Page 19: Changing The Batteries

    4.6 CHANGING THE BATTERIES To obtain access to the battery compartment, release the two slotted screws securing the carrying handle and ease back the upper half of the inst rument case, Remove the battery cover by pressing firmly downwards and sliding it towards the front of the instrument.
  • Page 20 Replaceable parts Chapter Introduction This chapter lists replaceable parts in alphabetical order of their circuit The following abbreviations and symbols arc used : references. switch battery socket capacitor SK T t ransistor Carb : carbon . variable diode wi rewound meter value selected during test;...
  • Page 21 Circuit reference Description M.I. code Carb IOOMQ 2% 24681-999 Met film IOMO 1% IW 24767-999 Met ox IMO 2% 24573-145 Met film IOOkS2 2% lw 24773-321 Met film 101<2 2% åw 24773-297 Met film 1.11<2 2% åw 24773-274 Met film 101<2 2% åw 24773-297 Carb IOMQ 10% 1/8W 24321-885...
  • Page 22 Chapter Circuit diagrams Circuit notes COMPONENT VALUES Resistors: no suffix = ohms, k = kilohms, M megohms. Capacitors: no suffix = microfarads, p picofa rads. -t = value selected during test, noruinal value shown. SYMBOLS arrow indicates clockwise rotation of knob. etc.
  • Page 23 RIG O STANOâRO'ZE • TENS UNITS 100. Fig. 7.1 Moisture meter 933C (la)

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