Page 1
Operating
Instructions
Avometer
Model9
Mk.4
Page 2
CONTENTS
SWITCH
During
to
except
transit,
'D.
C.'
'A.
Symbol
TRANSIT
the
and
the
C.'
or
,...._,
~
o-v
Q
n
a
.......
,...,
,.._
@ Avo Limited, 1971
*
POSITION.
right-hand
left-hand
'RESISTANCE.'
Alternating Current
Direct Current
Cut-out
Movement
Ohms
Moving Coil
Rectifier instrument
For horizontal
For
aoc./doco
Flash tested at 6kV
switch
switch
Definition
(doco)
reverse
use
use
should
to
any
(aoco)
control
be
set
position
REVoMoCo
Table
of
Ranges
General
Limits
Design
Range
The
Scaling
Movement
Overload
Replacement
Replacements
Operation
Current
Voltage
Resistance
Insulation
Low
Accessories
Servicing
Table
Circuit
Description
of
Accuracy
and
Controls
Movement
Reverse
Protection
of
Measurement
Measurement
Measurement
Resistance
Resistance
D.C.
Voltage
Current
D.C.
Shunts
Resistance
Replacement
of
Components
Diagram
Construction
Control
0 0
of
Internal
0 0
Instrument
Measurement
Measurement
Multipliers
Transformers
Range
Batteries
0 0
Battery,
Extension
Cell
Unit
and
Fuse
3
3
4
5
5
5
6
6
6
7
7
8
8
8
9
11
11
12
13
13
13
13
14
15
16
Page 3
OPERATING
INSTRUCTIONS
TABLE
Resistance
0-200
0-20
0-200,000
0-2,000
0-2·5
A range
ranges
multipliers (up
current transformers
OF
RANGES
D.C. D.C. A.C.
Voltage
3,000
v.
1,000
V.
600V.
300V.
100V.
30V.
10
v.
3·0
v.
Current
10
A.
1 A.
100 mA.
10
mA.
1
mA.
300f.1.A.
50f.1.A.
Voltage
3,000
1,000
300V.
100V.
30V.
10V.
3·0V.
megohms-with external voltage or external unit
megohms, (200,000 ohms
mid-scale}
ohms (2,000 ohms mid-scale) contained
ohms (20 ohms mid-scale)
ohms
(with
external unit)
of
accessories is available
of
measurement.
to
30kV)
d.
c.
and
a resistance range extension
to
These
include
current shunts
unit.
V.
v.
extend
(125mV
the
i:J.c.
A. C.
Current
10
1A.
100
10
self-
normal
voltage
drop),
A.
mA.
mA.
GENERAL
The Avometer
in general being accomplished by means
· knobs. All tests, except those on the 3,000
make
DESCRIPTION
use
of
the pair
is
extremely simple to
of
terminals at the base
use,
range selection
of
two
of
switch
V.
ranges,
the instru-
ment.
A clearly marked 5 in. (127 mm.) scale
divided graduations to match
and in addition there
mirror permits readings
with
made
The meter
great precision.
is
supplied complete
100 and 300 scale markings,
is
an
ohms scale. An anti-parallax
of
the knife edge pointer to be
with
rubber-covered leads. The remote ends
fitted
with
the Avo Long
spring clips, which may be interchanged
Reach
Safety Clips Mk. 2 supplied
has
a pair
of
the leads
uniformly
of
special
with
with
instrument.
Avo Long
Reach
Safety Clips Mk. 2 have been introduced
to enable connections for test purposes to be made at
what
are
ation will show that they
exception
compressing the stem into the body
normally inaccessible points on a chassis. Examin-
are
of
completely insulated
the jaws at one end, which can
of
with
be
opened by
the clip. Rigid
connections to wiring can thus be made by this insulated
device in complicated wiring systems where other types
larger clip could .not
short circuits.
It
should
be
attached, or
be
noted that they
if
fixed might cause
are
not suitable
for high current.
are
the
the
of
3
Page 4
OPERATING
INSTRUCTIONS
LIMITS OF ACCURACY
The instrument
used face upwards, in
the case
In
have been chosen
on very
of
A.C.
over effective range.
A.C.
range.
small deflections.
D.C.
Voltage.
half-scale deflection.
the full-scale value.
D.C.
Current.
Voltage*.
Current*.
Resistance.
The 'effective range' in accordance
Specification
D.C.-from
A.C.-from
4
will
produce its highest accuracy
which
position
of
voltage measurements, successive ranges
to
obviate the need
2%
of
indication between full-scale and
Below
half-scale deflection. 1%
1%
of
full-scale value.
Up
to 300
V.
(25-2,000
2·25%
3%
of
reading at centre scale.
89/1954
0·1
0·25
is:
of
scale-range
of
scale-range to full-scale value.
2·25%
Hz.).
of
full-scale value over effective
to
full-scale value.
it
has been calibrated.
for
taking readings
of
full-scale value
with
British Standard
when
It
will
be noted that
ranges,
the instrument meets the requirements laid
Section 6
for
Instruments.
*The instrument is calibrated
change in readings, due
15
ranges or on a.c.
On the 3V a.c. range the change should
Inasmuch
on 'a.c.'
of
the wave form
for their accuracy
also upon the maintenance
Since the form factor (r m.s.
of
a sine wave
calibrating the meter
values on the assumption that the normal sine wave
encountered.
form distortion can occur
the form factor and
but
when
producing high readings, and peaky
of
5 in.
(127
Hz and
15
as
proportional to the mean and
the user should recognise the possibility
using distorted wave forms, squarish wave shapes
with
the exception
the British Standard Specification
mm.) scale-length Industrial Portable
for
to
kHz) should not exceed
voltage ranges between 1
rectifier moving coil instruments give readings
which
not
is
1·11, this has been taken into
Generally speaking, considerable wave
variation in frequency (between
they
only
which
resulting accuracy
are
upon their initial calibration,
of
value divided by mean value)
does, therefore, indicate r.m.s.
without
of
the d.c. voltage
use at 50 Hz
2%
on a.c. current
OV
and 300V.
not
exceed
not
presented, they depend
a sinusoidal wave form.
the r.m.s. value
account
appreciably affecting
of
measurement,
of
some error
ones,
low
readings.
down
89/1954
but
the
4%.
but
in
will
be
in
Page 5
OPERATING
INSTRUCTIONS
DESIGN
The instrument consists of a moulded panel on the inside of
which
resistors, shunts, transformer, rectifier, etc., together
the movement. The panel fits
the
is provided
accomplished automatically by means
indicate on the engraved panel, the range in use. These
switches
being arranged
a feature
When the instrument
coil
pliers,
introduced.
RANGE
The left-hand knob provides all the d.c. current and voltage
ranges (except 3,000 V.) and the right-hand knob the
a.c. ranges (except
ranges. These knobs are
d.c. readings can
switch
range
be set
AND
CONSTRUCTION
is mounted the
joint
being rendered dust proof,
to
facilitate portability. The main
are
of generous and robust design, the contacts
to
which
is
associated
whilst
'make' before 'break' on adjacent ranges;
provides a factor
is
set
with
on a.c., diodes and a transformer are also
CONTROLS
3,000 V.) and also the resistance
has been set
selected,
for
a.c.
only be made after the right-hand
to
d.c., and the left-hand switch to the
a.c.
readings call
(it
must not be left at RESISTANCE) and the
whole
of
the
switching
into
a robust moulded case,
whilst
of
of
for
a universal shunt and series multi-
electrically interlocked so that
safety in use.
operation on d. c., the moving
for
the left-hand
apparatus,
a carrying strap
switching
two
knobs
which
switch
with
to
right-hand
require the
the right-hand one to the desired range.
If
the switches are inadvertently left
simultaneously, there is no circuit through the meter, and
it
is
misleading readings.
is
The main ranges are engraved on the
switches, and arrow heads on the knobs indicate the
range selected. The 3,000
available by means
Wide coverage in resistance has been achieved by having
a
fundamental range
with
In addition, a 200-megohm range marked
using
Range Extension
THE
The moving coil consists of
wound
stantan in order
compensation
is pivoted on hardened and highly polished steel pivots
between
switch
at the range required. Resistance tests
left-hand
thereby safeguarded against accidental damage or
ranges
of x 100
an
external d.c. voltage source or the Resistance
switch
to
be set
V.
of
the
as
and..;-1
unit
described on page 13.
a.c. and d.c. ranges are
two
special terminals so marked.
marked on the scale, together
00
to
to
RESISTANCE and
panel around the
supplement it.
MOVEMENT
an
with
copper wire and supplemented
to
reduce temperature error. Additionally
is
provided
conical spring-loaded jewels, and
by
aluminium alloy former
a thermistor. The moving coil
to
actual ranges
'INS'
is available,
with
swings
actual
Con-
in a gap
5
Page 6
OPERATING
INSTRUCTIONS
energised
associated
bronze hair springs
current to the moving coil, and to provide controlling
torque. A knife edge type
fine readings
balanced and damped so that the pointer quickly comes to
rest.
by
two
magnetised and aged Hycomax blocks
with
mild steel pole pieces.
are
fitted
to
be taken,
Two
for
the purpose
of
pointer is fitted enabling very
whilst
the whole movement is
phosphor
of
carrying
SCALING
The scale plate has three main sets
approximately 5 in. (127 mm.) length, the one being
resistance measurement and is marked
The second
and
apart. The third scale, calibrated
is used for current and voltage measurements.
MOVEMENT
is
marked
is
for current and voltage (both a.c. and d.c.)
0-100
with
divisions approximately
REVERSE
CONTROL
of
markings. each
0...:.300
0-200,000
has
60 divisions,
ohms.
1!
of
for
mm.
It sometimes happens that d.c. voltages may be required
both positive and negative to a reference point, or the
direction
the matter
button (REV. M.C.) is provided.
polarity marked on the terminals is for normal
not
of
flow
may be reversed. In order to simplify
of
lead alteration, a movement reverse press
apply when the button
is
pressed.
It
should
be
noted that the
use
and does
6
OVERLOAD
Apart from the ability
features
cut-out
protection to the whole
of
this device
conducting experimental work,
feeling
experimental
these can be easily ruined by inadvertently applied overc
loads, whereas the Avometer is so well protected that
withstand considerable mishandling.
If
an
overload
springs from its normal position in the panel. thus breaking
the main circuit, and this knob
to render the instrument again ready for
to note that the
instrument
· fault which caused the overload should be rectified before
the meter is reconnected.
The mechanism is brought into operation by the moving
coil coming into contact
scale position. There is, in addition, a second release at the
zero end,
loaded
almost complete protection to the meter,
guaranteed to fulfil completely its function in the very
PROTECTION
to
do
of
the instrument is the provision
which gives a very high degree
will
of
mental
ease
work
is
applied
cut-out
is
connected to
so
that the
in reverse. Although the overload mechanism gives
its job, one
of
the instrument. The incorporation
be found to be
and confidence. When conducting
with
conventional moving coil meters,
to
the meter, the cut-.out knob
should never be reset when the
an
with
cut-out
is tripped
of
the most attractive
of
an
automatic
of
overload
of
particular value when
for
it
imparts to the user the
it
has
only to be depressed
use.
It
is
important
external circuit, whilst the
a trigger just beyond its
if
the meter
is
it
cannot be
over-
can
full-
Page 7
OPERATING
INSTRUCTIONS
worst cases
across the meter when set to a current range.
noted that mechanical shock to the instrument
times trip the
reset, using direct pressure and
button, the instrument
protection is provided on resistance ranges by a fuse
connected in the 0 and
diodes connected in the
across the movement provides further protection should
a.c. be applied when the instrument
d.c. range.
REPLACEMENT
AND
In the battery compartment under the instruction plate,
which
is mounted a
1 A fuse and a spare fuse. The batteries should be examined
from time to time to ensure that the
leaking and damaging the instrument. This condition will
generally occur only when the cells
If
it
several months,
be removed to prevent possible damage.
When
battery must
markings
of
misuse, such
cut-out
mechanism. The
lying face upwards. Additional
0+
OF
INTERNAL
FUSE
can be removed by means
15
V.
battery and a 1 i
is known that the meter
replacing batteries, the 1 i
it
is preferable that these batteries should
be
of
inserted
polarity inside the battery box.
as
the mains being connected
without
0+
100 ranges and protective
1
00
range. A diode connected
It
should
will
cut-out
is
should be .
twisting the
connected to a
BATTERY,
of
a single DZUS fastener,
V.
cell together
electrolyte
are
nearly exhausted.
is
going to stand unused for
V.
with
cell and the
the poles to match the
be
some-
CELL
with
is
not
15
V.
REPLACEMENTS
1·5
V.
cell, 1 ~ in. dia. x
overseas, Berec) U.2.
such
as
Ever
is
a
~uitable
Part No.
PLUG-IN
When ordering replacements, the following description and
part numbers
Connector
Connector No. 2 (Red)
Clip
Long Reach Safety Clip Mk. 2 (Red)
*If
a
these part numbers
(with hook terminations)
Ready B.121.1f 8121 is unobtainable a
replacement. This requires
5140-015/016
TYPE
should be quoted:
No.2
(Black)
2!
in., such
15
v.
battery, 1 n in.
for satisfactory fitting.
LEAD
are
not
quoted, the older type
will
automatically be supplied.
as
WARNING
Special
service television receivers
currents
care
capacitors
must be taken when using the instrument
of
large capacitance,
or
other apparatus employing
for
the inclusion
components in a circuit may mean that
may
flow
when the apparatus is switched on.
very
Such surges produce a peaky wave form,
are
of
only a
few
these peaks
milli-seconds duration, they
may·never-the-less, puncture the instrument rectifiers
Ever
Ready (or
Xi
in. X 1 i in.,
an
Avo adaptor
Part No.
20913F*
20913E*
12381 B
214438
heavy
and
although
of
of
8154
leads
to
such
peak
7
Page 8
OPERATING
INSTRUCTIONS
OPERATION
The meter is intended
by any chance
set
by
means
The leads fitted
clips,
as
of
meter terminals in all cases except when measuring
voltages over
When measuring current or voltage, ensure that the
instrument
(either a.c. or d.c.) and then choose a suitable range before
connecting
always
switch
there being
switch
position is changed.
Do
not
to
a blank position.
The instrument is flashed tested at
the meter be used
of
3,000
the circuit (near earth potential).
be adopted other suitable safeguards must
OF
INSTRUMENT
for
that
of
the screw head on the panel.
required, should be connected
1,000
is
set
to
up
to
to the highest range and
no
necessity
however.
V.,
it
should be kept at the
use horizontally. Should
the pointer is
with
Long Reach Safety clips Mk. 2
V.
match the type
the circuit under test. When
switch
off
with
accessories on circuits in excess
not
of
to
disconnect the leads
by
rotating either
6,000
If
it
on zero. it may be so
to
source
work
V.
a.c.,
low
potential end
this procedure
happen
the
lower
to
be measured
in
downwards,
of
the
but
be
applied.
doubt,
as
knobs
should
cannot
or
pair
the
of
CURRENT MEASUREMENT
To measure current, the instrument should be set
suitable a.c. or d.c.
with
the apparatus
range, and then connected in series
to
be tested.
8
to
Generally speaking, the
is
negligible,
circuits, the inclusion
appreciably
prevail. The potential
terminals
the
50
volts. In the case
Standard meter leads have a resistance
Care
should be taken to ensure that the circuit is 'dead"
before breaking into
VOLTAGE
When measuring voltage, it
priate range
the source
magnitude
but
its actual value is
highest
appropriate selector
by
step, until the most suitable range has been selected.
If
the voltage should exceed 1
should be set
the negative lead should be transferred to the appropriate
a
3,000
making connections
should be entirely avoided
but
below
is
in the order
microamp range
MEASUREMENT
of
·a.c.' or "d.c.' and connect the leads across
of
voltage
of
the voltage is
range,
connect
to
V.
terminal. Great care must be exercised
power
in cases
of
the value
of
of
a.c.,
it
unknown,
up
switch,
measure 1 ,000
to
absorbed in the instrument
of
low
a meter may reduce the current
drop
500
which
it
is less than
to make current measurements.
to
be measured.
and
a live circuit, and the procedure
if
voltage heavy current
which
at.
mV. on all d.c. ranges, except
is
necessary to set the
within
if
decreasing the ranges step
V.
possible.
would
f.s.d., across the meter
has a
drop
350
of
0·02
the range
set the instrument to its
below 1 ,000
,000
V., the instrument
as
described above,
mV. on all ranges.
otherwise
of
125
ohm
per pair.
appro-
If
the expected
of
the meter.
V.
rotate the
milli-
but
when
Page 9
OPERATING
INSTRUCTIONS
When measuring high a.c. and d.c. voltages (say above
800
V.) unless the common positive terminal
earthy or connected to
the instrument is touched during a reading.
On d.c. ranges, the meter consumes
full scale deflection, this sensitivity corresponding to
20,000
D./V.
scale deflection
(2,000 D./V.). The
range consumes 1
maintains a high degree
tests
discussing the problem
well
to
where the current is
resistance between the source and the
measurement
voltage
connected.
sensitive,
under test, thus causing a higher
mentioned, and thereby causing the
point
Owing
this effect is unlikely to be
few
instances. A practical example
taken
on a television set or the tapping on a potential divider,
In the case
is
up
to 15 kHz on ranges
draw
attention to the
is
to
be
higher normally than
All current consuming voltmeters, however
draw
current to varying degrees from the circuit
of
measurement.
to the high sensitivity of the
into
account is in the measurement
earth, errors
of
obtained
10
0 rnA. at full scale deflection. The meter
limited because
to be made, it is possible
a.c. ranges above
with a consumption
V.
range is
of
accuracy
of
measuring voltage,
of
will
only
50
1000
D./V.
for
up
to
300
fact
that in certain circuits
of
the presence
point
when
volts
drop
in the resistances
voltage to fall at the
Model
importance except in a very
of
where
is
be introduced if
audio frequency
V.
for
9 on d.c. ranges,
of
either
microamps at
10
V.,
full
of
0·5mA.
The 3
V.
a.c.
a.c. Whilst
it
would
be
of
at
which
the actual
the meter is
it
might
e.h.t. voltage
be
where the resistances are so high
with
the resistance
generally possible to use a meter
absolutely necessary, and in such a case the higher meter
resistance causes
be the case.
for
reasonable accuracy should be attained.
it
When
voltage developed across a high resistor it is sometimes
preferable to insert the meter in series
measure the current
, meter, in milliamps, multiplied
in thousands
a
RESISTANCE
a
There
ohms
upward and
contained ranges make use
successive ranges are on 1
very
On resistance ranges, the meter must
from its
a resistance zero corresponding to the
of
and,
is essential to obtain
are
three self-contained ranges covering from
to
20
wide
coverage
normal instrument zero,
the meter. Before carrying
if
necessary, adjustment should
of
the meter on the range in use.
less disturbance than
At
the same time adequate pointer deflection
flowing.
of
ohms,
will
give the developed voltage.
MEASUREMENT
megohms, and provision is also made for both
downward
extension
with
three ranges.
of
out
as
to
on
a higher range than
would
an
accurate indication
The reading given upon the
by
the value
of
these limits. The self-
the usual series circuit, and
00
:1
ratio,
which
but
must have, in addition
full scale deflection
tests
for
resbtance a check
be
be comparable
otherwise
of
with
it
and to
of
the resistance
permits
not
merely start
carried
out
It
the
0·5
is
of
to
9
Page 10
OPERATING
ensure that when the leads
.actually indicates zero ohms, irrespective
of
the battery (within the limits
method of adjustment
Owing
to
accuracy, but it should
centre
around deflections corresponding to 1
scale deflection.
Resistance test should never
which
On three ranges which utilise the internal source
it
at the negative terminal of the instrument when set for
resistance tests. This fact may
resistance
direction
therefore, depend upon the direction in which the test
voltage
cases
When measuring the leakage resistance
capacitor the negative
connected to the positive terminal
the ohms x 1 00 range employed.
Before making resistance tests the pointer should
adjusted to zero in the following sequence:
the nature
scale, increasing up
are
already carrying current.
should
be
remembered that a positive potential appears
of
of
the current through them, and readings,
is
applied. quite apart from its magnitude. Such
include electrolytic capacitors and rectifiers. ·
Set left-hand switch at 'RESISTANCE'.
1.
INSTRUCTIONS
are
joined together the meter
is
described later.
of
the scale, it is not
be
within
to
about 10%
be
carried out on components
some components varies according to the
be
lead from the meter should
of
the condition
of
adjustment). The
easy
3%
importa,nt because the
of
to define the
of
the reading about
of
the indication
0%
and
90%
of
voltage,
of
an
electrolytic
the capacitor. and
of full
be
be
2.
Join
leads together.
On
the n range, adjust to zero by means
3.
knob marked
4.
On
the
the knob marked 'ZERO 0-;. 1 00'.
5.
On
the ·n x 1
the knob marked 'ZERO n x 1 00'.
To test a resistance, set the right-hand switch at the range
required, the
component.
Resistance
should
ranges.
If
on joining the leads together
zero ohms setting, or
will
battery or
that a discharged unit should not
since the electrolyte might seep through and cause
damage to the meter.
on the
box should
NOTE.
such a manner that although
15 volts, its internal resistance has increased so much that
some
is
be
divided or multiplied by 1 00 on the other
not remain constant, but falls steadily, the internal
cell concerned should
.Q-;. 1
It
can so happen that a
loss
of
'ZERO
'.Q-;.
1
leads being connected across the unknown
read
directly on the
00
range, the 1 A fuse located in the battery
be
checked.
accuracy can occur on the high resistance
n·.
00'
range, adjust to zero by means
00'
range, adjust to zero by means
·n·
range, but indications
it
if
furthermore the pointer position
If
it
is impossible to obtain readings
is impossible to obtain
be
replaced.
be
left in the instrument,
15-volt
battery may age in
it
indicates a potential
It
is
important
of
the
of
of
two
of
10
Page 11
OPERATING
INSTRUCTIONS
range {f.! x 1
time,
is
it
short circuit current on the
fails
discarded.
INSULATION
Two
or other source
160
ANCE'
leads should be connected
should be brought to zero on the ohms scale
the adjuster marked 'ZERO f.l X 1
the
unknown
value
1,000. Resistances up
read on this range.
The
alternative method makes use
Extension
LOW
The meter setting marked L.R.
Range Extension Unit. The method
the section covering accessories.
00).
If
or
if
errors are suspected on the high resistance range,
worth
to
give a reading greater than 25mA.
courses are open. the first merely calling
V.
The left-hand
with
will
be that
Unit', described later.
RESISTANCE
the battery has been in use for some
while removing the battery and checking its
RESISTANCE
of
the right-hand
resistance in series
shown
100
mA. d.c. range
MEASUREMENT
d.c. voltage in the order
switch
should be set at 'RESIST-
switch
at
to
on the ohms scale multiplied
to
200 megohms can, therefore, be
MEASUREMENT
is
'INS'
the battery. The pointer
oo·.
To test, connect
with
the meter and its
of
the 'Resistance Range
for use
with
of
use is described in
If
the battery
it
should be
for
a battery
of
130
V.
to
and the meter
by
means
of
by
the Resistance
11
Page 12
ACCESSORIES
A range
ranges of measurement. These include d.c. voltage
multipliers
current transformers and a resistance range extension
unit,
D.C.
General
(say above
either earthy
if
Combined
A combined 1
for use
connected to the
recommended
as
end, e.g.
negative
between the
terminal
the meter must be connected
supply being measured using the
provided. A cap
position over the high
It
leads are handled
Protection is provided
of
accessories
(up
to
as
follows:
VOLTAGE
Note:
When measuring high a.c. and d.c. voltages
SOOV.)
or
the instrument
possible and the
is recommended that neither the meter, multiplier nor
connected to earth, errors
10kV.
OkV.
with
the instrument. The Multiplier should be
that
when
line
is
earthy, the
point
of
the meter. In addition, the
is
available
30kV.) d.c. current shunts (125mV.
to
extend the normal
MULTIPLIERS
unless the common positive terminal
is
touched during a reading.
and
30kV. d.c. Voltage
and 30kV. d.c. multiplier is available
Avo
meter set
the meter
Multiplier
measuring an e.h.t. voltage
of
positive potential and the positive
is
provided
voltage terminal
whilst
by
to
is
kept
used at the high potential
Multiplier
to
which
high voltage tests are in progress.
a resistor connected permanently
will
be introduced
Multiplier
the 1
OV.
d.c. range.
as
near earth potential
should be connected
low
the
low
low
should always be in
when
potential end
potential
potential lead
not
in use.
drop),
It
the
of
the
1 2
is
is
of
across the multiplier terminals thus preventing the full
being present should the meter be disconnected.
voltage
30kV.
D.C
Multiplier
A 30kV. d.c.
meter set
direct in kV. on the
most
end
the positive
potential. This method
indication
not
think
when
In general
nor leads are handled
progress, and a
for
connection
CURRENT
Transformers are available
when
meter set
transformer before current
and care
If
this course is
will
through the primary. Transformers
amp. are
Multiplier
to
its
important
of
the circuit and the mu!tiplier connected
or
with
it
desirable to use the moving coil reverse button
measuring
we
recommend
is available
1,000
V.
d.c. range, readings being made
0-100
to
ensure that the meter
negative terminal whichever
of
the meter earthy is recommended
special lead
to
connection to get forward pointer
high
voltage.
whilst
the high potential point.
for
use in series
scale and multiplied
that
neither the meter, multiplier
is
provided
is
kept in the earthy
high voltage tests are in
with
TRANSFORMERS
to
set
to 1 OOmA.
to
its 1
OOmA.
should be taken that the
not
appear at the secondary terminals,
now
followed, quite a considerable voltage
replaced
extend the a.c. current ranges
a.c.
It
is necessary to connect the
range
to
is
by
current Ratio Transformer.
the secondary
passed through the primary,
cut-out
if
for
30. 100, and
with
the
by
300.
It
to
either
is
at high
as
we
do
the multiplier
of
the
is
in position.
current passes
300
is
Page 13
ACCESSORIES
CURRENT
This transformer replaces
formers previously manufactured
a.c. current measurement.
range
scale values
packed
D.C.
The
Shunt
terminals in series
meter. set
be connected
blocks.
The
Avometer
scale deflection, a value
with
across the shunt is directly proportional
which
meter
terminals, the instrument indicates correctly over its
its
entire
Shunts available: 30,
RESISTANCE
This accessory enables
and
RATIO
up
to
1.5A
up
with
each transformer).
TRANSFORMER
the
It
to
to
may be used on
provide a comprehensive range
600A
a.c. (see operating instructions
SHUNTS
should be connected by means
to
the
full-scale current
may
is
directly proportional
scale length.
low
resistance measurements.
its
flow
with
5011-A
to
when
through
RANGE
the
(125mV.) d.c. position should then
the
two
small studs on
so set, consumes
which
of
it
and since the
100
and
EXTENSION
the
meter
30A. 1 OOA.
to
circuit
is negligible in comparison
the
shunt. The
to
the
300
and
extend the ranges
to
millivolt
amp.
300A
any
a.c. current
of
its
be measured. The
only
two
the
shunt
50iLA at
millivolt
to
any current
deflection
drop
UNIT
to
be used
for
It
is complete
both
trans-
of
of
full
main
end
full-
drop
on
the
across
high
with
batteries (except in some instances) and
facilitate tests. The device should be connected
lower
terminals on
to
is set
'SET
connected
deflection should
n x 1
to
value
a range
· For
set
at 'SET',
terminals and adjustment
out
should then be moved
pointer deflection on a
Full scale deflection corresponds
avoid discharging the batteries, immediately tests have
been
the
unit
the
position and
00'
knob. The
'TEST,
is
that
of
low
resistance measurements
to
position
the
by
means
completed the resistor should be removed
unit, its
disconnected
REPLACEMENT
Replacement batteries 1 ·5
as
Ever Ready.
-1
+.-
in.
xi
the
meter. For high resistance the meter
'n x 1
00'
position,
the
to
the
and the reading on the ohms scale noted. Its
shown
200
unknown
switch
unknown
'High'
be performed
Unit
multiplied
megohms.
'L·R'
and
of
the 'ZERO
set
from
terminals.
the
resistor connected
to
to
the meter.
the
resistance
Adjustment
by
switch
should then be rotated
by
1,000
the
Unit
switch
to
full scale
n·
knob. The
position marked
uniformly
to
the
'low
set' position, and the
BATTERIES
V.
(or
overseas, Berec) U.2 Four
in. x
2-ft
cell-1 ~ in. dia. x
in., such
as
Ever Ready 8.123.
switching
to
Unit
switch
of
30
to
the
to
Unit
2~
V.
at
then be
full scale
'ZERO
should be
the
'Low'
carried
switch
and
the
from
in. such
batteries
should
means
corresponding
Avometer
should be placed
deflection
'TEST
divided scale noted.
2-! ohms. In order
to
the
the
to
to
13
Page 14
SERVICING
TABLE
OF
COMPONENTS
Due
to
the high operational standards maintained
out
our
organisation, and the close limits
work,
breakdowns are comparatively rare, and can often
be traced to transit damage or
the Company
instrument should require servicing or a calibration check,
we
at Avo have the
your
instrument
For those customers
skill and equipment to carry
requirements, spares are
To obtain the correct spares
required and state its position in the instrument. Where
applicable state the circuit reference number. Should you at
any time have to return
for
repair pack
our
engineers
outside the U.K.
for
their territory.
14
cannot
be held responsible If, however,
knowledge
to
the highest possible standard.
it
carefully and enclose a note informing
of
the faults
should contact the
careless handling.
and equipment to repair
who
feel they have the necessary
out
available from
item, identify the component
your
which
their
instrument
you have found. Customers
Avo
through-
within
which
for
own
servicing.
Avo
Limited.
to
the Company
representative
we
which
your
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24
R25
R26
1-11 kO
1-11 kO
7·5k0
6200
3·6k0
1·24k0
90
8200
0·050
0·450
4·50
3·00
420
4500
3000
8670
8·33k0
197·5k0
1·8MO
4MO
6MO
8MO
40MO
4MO
4k0
8·2k0
R27
R28
R29
R30
RV1
RV2
RV3
RV4
RV5
RV6
RV7
RV8
01
02
03
04
05
06
07
C1
C2
C3
Th1
F1
B1
B2
2000
57·5k0
400k0
10k0
5000
5·5k0
5·5k0
5000
50
1k0
1000
1k0
OA47
OA47
BY
124
BY
124
BY
124
BY
124
BY
124
0·02f.LF±5%
270pF±5%
1000pF±5%
Va
1039
Fuse 1 amp
Battery
1·5
Battery
15
V.
V.
Page 15
SWITCH
CONNECTIONS
VIEW THROUGH FRONT PANEL SHOWING
SWITCH DISCS & CONTACT FINGERS ASSEMBLED
D.C. DISC.
100v30v10v
D.C.D.C.D.C.D.C.
A.C. DISC. A.C. DISC.
3v
15
Page 16
CIRCUIT DIAGRAM
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@a@
CL.OSED
'rt.',h+000
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l 'L.II: pOSITIONS
ONLY.
NUidBERS
..
CIII<;L£SOHSWITCHES~IITO
P.C
DISCSWITO<
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C<:lt<I'E-CTIOH50NOAG.C"O•I
1<:
Page 17
Part No. 6170-012
Avo
Limited
Avocet House
Dover,
Tel:
Kent, England
Dover 2626
Telegrams & Cables:
Avocet Dover
Telex: 96283
Print11d
in
l.
A
Men1borof
ah•
Thorn
Grov•
England
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