Marconi Instruments 933D Manual de usuario

Marconi

Instruments

Marconi Moisture Meter

Model

933D

Moisture

content measured to within

0.5% in a few

seconds.

Calibrations available for more than 200 different

substances.

Supplied with optional ISO or standard wheat and

barley scales.

Quick-loading compression cell eliminates packing

errors.

Compact, portable and battery operation.

Calibration check facility.

Instruction Manual

MOISTURE METER

933D

O Marconi Instruments Ltd 1992

Nopart of thisbookmay be reproduced or transmitted in anyform or by

any mecms, electronic or mechanical, including photocopying,or

recorded by any information storage or retrieval syston, without

permission in writing by Marconi Instruments Ltd.

Printedin the UK

Manual part no. 46882-171 D

Issue I

Apr. 92

EVEN HEADER

CONTENTS

ChapterI GENERALINFORMATION

1.1 FEATURES.

1.2 DATA SUMMARY.

1.3 ACCESSORIES.

Accessories supplied.

Accessories

available

Chapter2 OPERATION

2.1 Installation .

2.2 Controls and connections.

Balancecontrols

Electrode connections .......

Calculator scales .......

2.3 PREPARATION

OF SAMPLE.

Granular or powdery substances.... .

Fibrous material...

2.4 LOADINGTHECOMPRESSION

CELL

Sheets and boards (e.g. cardboard)..

2.5 READING

THEINSTRUMENT.

Set Scale.......

Set ZERO..

Read...

Conven to moisture content.

2.6 AVOIDINGERRORS

Sampling errors

Correcting for sample temperature

Chapter3 TECHNICALDESCRIPTION

3.1 CIRCUITDESCRIPTION

........

Chapter4 MAINTENANCE...................

4.1 INTRODUCTION............ ......

Screwfasteners......................

4.2 TESTING

Calibration.

Continuityof leads, etc...

Læakage......

4.3 CLEANING

4.4 LUBRICATION.

4.5 ACCESS

ANDLAYOUT.

4.6 CHANGING

THEBATTERIES

Chapter5 Unassigned

Chapter6 REPLACEABLEPARTS.

Introduction

Ordering.

Chapter7 CIRCUIT DIAGRAMS

Circuit

........ 17

.17

.23

46882-171 D

Apr. 92

Chapter 1

GENERAL INFORMATION

1.1 FEATURES

The moisture

meter measuresthe percentagemoisturecontent of a wide rangeof hygroscopic

materials, particularly those of organic origin, in the field or laboratory.

Thetest cell which is of the compression type and is stowed in the instrument when not in use, is

suitable

for granular,powdery or fibrous substancesand for specimensin the form of sheetsor

boardsup to one inch in thickness. An important function of the test cell is the applicationof

considerable

pressureto the specimen under test in order to bring the sample to a uniform state

and minimize packing errors.

Directreading temperature-correcting calculator scales can be slipped onto the instrument for the

commonermaterials,such as cereal grains, cigarette tobacco and rice, while a large numberof

calibration charts are available for substances ranging from apple rings to wool socks.

Thestandard

modelis poweredby two 9 V internaldry batteries.

Fig. 1.1 Themoisturemeter withcompressioncell electrode and calculator scalefitted

46882-171D

Apr.92 3

GENERAL INFORMATION

1.2 DATA SUMMARY

RANGE: contents from below air-dry to near saturation.

Moisture

ACCURACY: The basic accuracy of the instrument is ±().5% m.c., but

variations

due to the nature of the samples may reducethisto

m.c. The accuracy tends to fall at high moisture contents.

SELF-CHECK

FACILITY: nie instrumentmay be checked against the internal standard

resistance

of I MQ at a meterreadingof 40.

CALIBRATION: The calibrations,

which are made by comparison with standard

analyticalprocedures,are based on ground sampleswherever

possible.

SCALES: The standard apparatus includes the Calibration Data for the

cereal grains and agricultural seeds.

Cereal

grains

and 9 to 25%for wheat,rye and maize; 8 to 24% for barleyandoats.

agricultural

seeds: Temperature

-l to 38

0C (30 to 100

0F). The scales are basedon

oven drying for four hours at 1200C (2480F).

Tables are provided covering agricultural seeds.

Flour

and

wheat: 9 to 25%for groundwheat; 10

to 20%for flour. Temperature

-l

to 380C(30 to outside the range 10 to 300C(50 to 860F)

there may be a slightfall in accuracy. The scales are based

oven dryingfor four hours at 1200C

(2480F). Tables are given

for othermill stocks and products.

Cigarette

tobacco: 8 to 20% for 'cigaretterag' (equivalent to cut whole leat) and9 to

21%for cut lamina. Temperature 10to 300C(50 to 860F).The

scales are based on oven drying for sixteen hours at 1000C

(2120F).

Tickbeans: 9 to 22.5% for ground beans. Temperature 10 to (50 to

860F). The scale is based on oven drying for fifteen hoursat

105

0C (22 IT).

446882-171 D

Apr. 92

10to 22% for polishedrice. Temperature 10 to 300C(50 to

Rice: scale is based on oven drying for fifteen hoursat

860F).

105

0C (221O

F).

4 to 13%

for paper; 6 to 22% for chemical wood pulp and boards.

Paper: Temperature 10 to 320C (50 to 900F). Supplementary

information

is providedcoveringmanytypes of wood pulp,paper

and boards. The scales are based on oven drying to constant

weight at 102to 1050C (215.5 to 2210F).

SUPPLY: Internal batteries: two PP3 9 V or equivalent.

DIMENSIONS: Height

(197 mm)

Width

11i in

(28 mm)

Depth

5i in

(135

mm)

WEIGHT: 7 1b(3.1 kg) approximately.

1.3 ACCESSORIES

Accessories supplied

1CompressionCell Electrode Assembly type 43147-013 (Electrode 37582-106,Ring

37438-306,

Plunger 33646-701and 3 ft Connecting cable 43125-038).

2 One set of Calibration Data, 46883-036 - see under Accessoriesavailable. A set of

calibration

data comprisesa slip-on calculator scale and a booklet,card or sheet giving

supplementaryinformation on substancescovered by the calculator scale and in some

cases,alliedsubstances.

3 Thermometer.

4OneInstruction Manual Part number 46882-17ID.

46882-171

Apr. 92 5

GENERAL INFORMATION

Fig. 1.2 Themoisturemetershowingaccessories

Accessories available

1Standard Calibration Data:

Cereal grains and agricultural seeds

Flour and wheat

Cigarette tobacco

Tick beans

Polishedrice and paddy

Paper

TM 4473A/1

TM 4473A/2

TM 4473A/3

TM 4473A/8

TM 4473A/9

TM 4473A/10

2 Special Calibration Data; can be supplied to order for a wide range of materials.

3Smallgrinder;for grindingwholegrainetc.

4Spare Standard Electrode TM 4178A; for compression cell electrode assembly.

5 Two 9 V batteries: Exide type DT3. Ever Ready type PP3, Ray-o-Vac type R3 or Vidor

type VT3 or equivalent.

46882-171

6Apr. 92

Chapter 2

OPERATION

2.1 Installation

NOTE: lhe performance

of this instrument

may be impaired

by lengthy

exposure

to a damp

atmosphere. Dryingfor a short period in a warmdry atmosphere

willrestore

it to

give normalperformance.

Ensurethat the instrument is switched OFF before connecting

any leads and only

switchedon when actually taking measurements, hence prolonging the life of thebatteries.

2.2 Controls and connections

Balance controls

Theelectrical principle employed in the instrumentis the variationof conductivity

of the

specimen

with moisturecontent. Conductivity is measuredby adjusting

the coarse and fine

BALANCEcontrols to give a standard meter indication; the reading on thecontrols is theneasily

convertedinto moisture content by reference to the scale on the instrument or to a chart supplied

with it.

In addition

to the two BALANCE controlsthereis a rotaryswitchmarkedOFF-ZERO-

READand a ZERO knob for standardising the instrument taking a measurement.

NOTE: If either of the BALANCE controls becomes loose it must not be securedwithouttint

carrying out the standardisation test detailed in Sect.4.2.

Electrode

connections

The compressioncell electrode is normally stowed in the lower front compartment

of the

moisturemeter. Also inside this compartment are three sockets RED, GREENand BLACK.

Connect one end of the electrode 2-core cable to the RED and BLACKsocketsand connect the

otherend to the two socketson the compressioncell electrode

containing

the specimen;

wire

colours are not important. (The GREEN socket is not connectedto the compression

cell

electrodeon this instrument.)

Two other sockets labelled CALIBRATION CHECK are provided for connectionto the

REDand BLACKsockets for test purposes.

46882-171 D7

Apr. 92

OPERATION

Calculator

scales

If a scale is available for the substanceto be tested slide the scale into position see Fig.

1.1. If thereis no scale available then select the appropriatecalibration data sheet.

following sections give the general method of operating the instrument. Detailed

procedures

that apply to particular materials are given in the calibration data supplied for each

group of substances.

2.3 PREPARATION OF SAMPLE

Granular or powdery substances

The instrument may be used in two ways:

(a) On whole grain

(b) On the flour or meal produced by coarse grinding.

Testson ungroundgranularsubstancesare stronglyinfluencedby the surfacemoisture.

Testson whole grainsof wheat indicatesubstantially

the bran moisture. For this reasonit is

advisable

to test the sampleboth whole and ground,to give an indicationof the moisture

distribution as well as its average value.

The finenessof grindingis not importantbut the loss of moisturewhich may occur,

especially

withdampsamples,

mustbe minimised. Therefore avoid very fine grinding. After

grinding, flush out the grinder with the sample to be tested and discard the first ground sample.

Fibrous material

In general the procedure is the same as for granular materials.

The cavityfor the test cell should

be approximately

half filled with the specimen

until

packeduniformly,pressingthe specimendown in muchthe same manner as filling a pipe. After

the test the compressed plug should be about 1/16 inch thick.

2.4 LOADING

THE COMPRESSION CELL

The following description may appear complicated because each detail is mentioned but

the procedure will be found quite simple and convenient.

46882-171

8Apr. 92

OPERATION

(1) Unscrew

theclamp. Withdraw the test cell. Take out the plunger.

(2) See that the insulating ring is well seated on the electrode with its open end upwards. In

handlingthe electrode, hold by the edges. Do not handle the upper surface as this may deposit

moisture

onthe insulating surface between the two electrode rings.

(3) (a) For whole grains put enough into the test cell to form a single layer.

(b) For groundsampleshalf fill the test cell with meal. After thetestthe compressed

plugshouldbe about 1/16inch. Ensure that the sampleis lying uniformlyin the bottomof the

testcell; a gentle shake will ensure this in most cases.

(4) Insert the plunger and hold it down (to prevent the sample slipping to one side) thenslide

thecompletetest cell into the clamp.

(5) Screw the clamp down until the two parts of the cylindrical spring housing, mountedon

the end of the screw, become flush.

CAUTION The spring is compressed solid by about a half turn of the screw beyond

standardthrust at whichtests are made. The solidpointcan easilybe felt on the

tommy-bar. DO NOT ATTEMPT to tighten beyond this point as it is possible

for a strong operator to strainthe clamp.

Take electrode (A)

Add ring (B)

Half fill the cavity

then add plunger (C)

Screw the assembly down in

the clamp until flush at (D) (D)

(A)

46882-171

Apr. 92

(B) (C)

Fig. 2.1 Compressioncell electrodeassembly

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