Marconi TF 933C User manual

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

Contents
Chapter
1 GENERAL INFORMATION
1.1 Features
1.2 Datasummary
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 Readingthe instrument
Avoiding
errors
Chapter
3 TECHNICAL DESCRIPTION
3.1 Circuit description
Chapter4 MAINTENANCE
4. 1
4. 2
4. 3
4. 4
4. 5
4. G
Introduction
Testing
Cleaning
Lubrication
Access andlayout...
Changingthe batteries
Chapter 5 (not assigned)
Chapter6 REPLACEABLE PARTS
Introductionand ordering
Chapter
7 CIRCUIT DIAGRAMS
Ci
rcuit notes
Fig. 7.1 Moisture
meter
8
8
9
9
11
13
16
17
17
18
18
20
21
23
24
9.

Chapter
1.1 FEATURES
General information
Themoisturemeter measures the "jointurecontentof a widerange
ofhygroscopic
materials, particularly thoseol' origin, in the field or laboratory.
Thetest cell which
is ofthecompressiontype stowedin the instrument
whennot in use. is suitable for granular, powde oc I ous
substances
and
for
specimensin the form of sheets or boards up to one inch in thickness. An important
function
ofthetest cell is theapplication
ofconsidetal'le pressure to the specimen
undertest in order to bringthe sampleto a unif01Mi and minimizepackingerrors.
Directreadingtemperature-correcting calculator neales can be slippedonto
theinstrument
for thecommoner
materials, such an ceteal grains, cigarette tobacco
andrice, while
a large numberofcalibrationcha are availablefor substances
ranging
from applerings to wool
socks.
The standard model is powered by two9 V into
t
mal(l
rv batteries.
Fig.1.1 Themoisturemeter withcompressioncell electrode and
calculatorscalefitted
933C (1)

1.2 DATA SUMMARY
RANGE:
ACCURACY:
SELF-CHECK FACILITY:
CALIBRATION:
SCALES:
Cereal grains and
agricultural seeds:
Flour and wheat:
Cigarette tobacco:
Moisturecontents from belowair-dry to near
satu ration.
Thebasic accuracy of the instrument is
10.5%,
m.c. , but variations duc to the nature
of the samples may reduce this to m.c.
Theaccuracy tends to fall at highmoistu
re
contents.
The instrumentmay be checkedagainst the
internal standard resistance of 1 MS)
at a
meter readingof40.
The calibrations, whichare made by comparison
with standard analytical procedures, are based
on ground samples wherever possible.
The standardapparatus includesthe Calibration
Datafor the cereal grains andagricultural seeds
9 to 25%
for wheat, rye andmaize; 8 to 24%
for barley andoats. Temperature -1 to 38
0c
(30to 100
O
F). The scales are based on oven
drying for four hours at 120oc (248O
F).
Tables are providedcovering agricultural seeds.
9 to 25%
for groundwheat; 10to for flour.
Temperature -I to 38 oc (30to 100
O
F); outside
the range 10to 30oc (50to 86O
F) there may be
a slight fall in accuracy. The scales are based
on oven drying for four hours at 120oc (24801").
Tablesare givenfor other mill stocks and
products.
8 to 20%
for 'cigarette rag' (equivalent to eut
whole
lean and9 to 21%
for cut lamina. Tern
perature 10to 30 oc (50 to 86 O
F). The sea
are based on oven drying for sixteen hours at
100 O c (212 O F).
93.'lC
(l)

Tick beans:
Rice:
Paper:
POWER SUPPLY:
n
DIMENSIONS:
WEIGHT:
1.3 ACCESSORIES
Accessories supplied
9 to 22.
10 to
on oven
(221 010.
10 Co
to 30
oven
•und01').
fifteen le is based
1101
inhed rice. "l'entpevaturc 10
(00 0F). Thescale is based on
tilleen hours at 105
oc (221OF).
4 to 1:1
1
},
pulp and
to 90 OF).
G
to 22%)
for chemical wood
e10to 32 oc (50
remperature
Suppletnentary information is
providedcovering roanytypes of wood
pulp,
paper and can. The scales are based ono
ovendrying to constant weightat 102to 105 c
(215.5
to
Internal
equivalent.
Height
7 3/4 in
(197mm)
01").
: twoPP3 9 V or
Width Depth
Il .'1/8
in 5 1/4 in
mm) (135
mm)
7 1b(3.I Kg)
nppro.ximately.
1. Compression Cell Electrode Assembly typo 'I'M '1
1IOA(complete with Clamp
TC 22429, Electrode TM4178A, Ring 22,120/2. Plunger TB 22425/1 and
3 ft Connecting Cable TM 4130A).
Note: The clamp is nowsuppliedwithout
tho rubber handgrip still
shownin the illustrations.
2. (he set of CalibrationData, 'CM
4473A/I see under Accessories available.
Aset of calibration data comprises a slip -onealeulator scale and a booklet,
card or sheet giving
supplementary
informationon substances covered by
the calculator scale and in some cases, allied substances.
3. One4 BAhexagonalwrench, Marconi type 22951-006; for carrying out
the standardization
test detailed in Sect, 4.2.
4. OneInstruction Manual No. EB 933C.
933C
(lc) 5

Content
Fig. 1.2 Themoisture meter showingaccessories
Accessories available
Standard Calibration Data:
Cereal grains andagricultural seeds
Flour and wheat
Cigarette tobacco
Tick beans
Polished rice and paddy
Paper
TM 4473A/1
TM 4473A/2
TM 4473A/3
TM 4473A/8
TM 4473A/9
TM 4473A/10
Special Calibration Data; can be supplied to order for a wide range of tuatetoala.

3. Smallgrinder; for grinding wholegrain etc.
4. Spare Standard Electrode "I'M
4178A; lor eojnpression cell
5. Large Electrode Unit TM 4178A/.'I
(contplete Ring TC and I
'lunger
TC 22433/2); ror use withcompression cell elect rode to large
samples. Theunit has a (lia
tneter ol' Inches and holds about 10 Ins.
6. Two9 Vbatteries; F.xidetype Ever Itea€lv
type PP3, Ray-o-Vac type
or Vidor type VT3 or equivalent.
933C (1)

Chapter Operation
2.1 INSTALLATION
NOTE Theperformance of this instrument maybe impaired by lengthy
exposureto a dampatmosphere. Dryingfor a short period in a
warmdry atmosphere will restore it to givenormal performance.
Ensure that the instrumentis switchedOFF before connectinganyleads and
onlyswitchedon when
actually takingmeasurements, hence prolonging
the life of
thebatteries.
2.2 CONTROLS AND CONNECTIONS
Balancecontrols
Theelectrical principle employedin the instrument is the variation of conductivity
of the specimenwithmoisture content. Conductivity is measured by adjusting the
coarse andfineBALANCEcontrols to give a standard meter indication; the reading on
the controls is then easily converted into moisture content by reference to the scale on
the instrument or to a chart supplied with it.
In addition to the twoBALANCEcontrols there is a rotary switch marked OFF-
ZERO-READ
anda red ZEROknobfor standardizingthe instrument before takinga
measurement.
NOTE: If either of the BALANCE
controls becomes loose it must not be
secured without
first carrying out the standardization test detailed
in Sect. 4.2.
Electrode connections
•me compression cell electrode is normally stowed in the lower front compart—
of the moisture meter. Alsoinsidethis compartmelt are three sockets
labelled RED, GREEN
and BLACK. Connect the RED and BLACKsockets on the
893.w

compression cell electrode using the lead provided. Ensure that will' the
larger plugs goes to the main instrument and do not attempt to into
smaller sockets on the compression cell. Thore is no significance in
of the individual leads as there is no polarity to observe and the connectionn be
reversed withouteffect. The GREEN
socket ig not required for the
cell suppliedwiththis instrument and the other two sockets labelled CA
CHECK
are provided
for test purposesas described inChapter
Calculator scales
If a seale is availablefor the substance to be tested slide the scale into position -
see Fig. 1.1. If there is noscale availablethenselect the appropriate
calibration
data sheet.
The following
sections give the general method of operating the instrument.
Detailedprocedures that applyto particular materials are given in the calibration data
suppliedfor each group of substances.
2.3 PREPARATION OF SAMPLE
Granular or powdery
substances
Theinstrument may be used in two ways:
(a) wholegrain
(b) the flour or meal produced by coarse grinding
Tests onungroundgranular substances are strongly influenced by the surface
moisåare. Tests on wholegrains of wheat indicate substantially the bran moisture.
For this reason it is advisableto test the sample both wholeand ground, to give an
indicationof the moisture distribution as well as its average value.
The fineness of grinding is not important but the loss of moisture which may
occur, especiallywith
dampsamples, must be minimized. Therefore avoidvery
finegrinding. After grinding, flushout the grinder withthe sample to be tested
anddiscard the first ground sample.
Fibrous material
Ingeneral theprocedure is the same as for granular materials.
The cavity for the test cell should be approximately half filled with the specimen
tmtilpacked
tmiformly, pressing the specimendown
in muchthe same manner as
filling a pipe. After the test the compressed plug should be about 1.6 mm thick, or
3.2 mm for the large cell.
2.4 LOADING THE COMPRESSION
CELL
The following
description may appear complicatedbecause each detail is
mentioned
but the procedure willbe foundquite simple and convenient.
933C (1b)

(i) Unscrewthe clamp. Withdraw
the test cell. Take out the plunger,
(2) See that the insulating ring is well seated on the electrode with its open end
upua
rds. Tn
handling the electrode, hold by the edges. Donot handle the upper
surface as this maydepositmoisture on the insulatingsurface between the two
electrode rings.
(3) (a) For wholegrains put enoughinto the test cell to form a single layer.
(b) For groundsamples half fill the test cell withmeal. After the test the
compressed plugshouldbe about1.6 mm (or 3.2 mm for the larger test
cell). Ensure that the sample is lying uniformly in the bottomof the test
cell; a gentle shakewill ensure this in most cases.
(4) Insert the plungerandholdit down(toprevent the sample slipping to one side)
then slide the complete test cell intothe clamp.
(5) Screw the clamp down
until the twoparts of the cylindrical spring housing,
nummt.ed
on the end of the screw, become flush.
CAUTION The spring is compressed solid byabouta half turn of the screw
beyondstandard thrust at whichtests are made. The solid point
can easily be felt on the tommy-bar. DONOTATTEMPTto
tightenbeyond
this point as it is possible for a strong operator to
strain the clamp.
Fig.2.1 Compression
cell electrodeassembly
Takeelectrode (A)
Add ring (B)
Jlalf fill the cavity
then add plunger (C)
Screw the assembly downin
the clamp until flush at (D)
(A) (B) (C)
10