IS 1248-9: Direct Acting Indicating Analogue Electrical Measuring Instruments and Their Accessories, Part 9: Test Methods

30 Pages·2003·2.6 MB·English

by  Bureau of Indian Standards

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in order to promote transparency and accountability in the working of every public authority,
and whereas the attached publication of the Bureau of Indian Standards is of particular interest
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education and knowledge, the attached public safety standard is made available to promote the
timely dissemination of this information in an accurate manner to the public.
“जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ”
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“The Right to Information, The Right to Live” “Step Out From the Old to the New”
IS 1248-9 (2003): Direct Acting Indicating Analogue
Electrical Measuring Instruments and Their Accessories,
Part 9: Test Methods [ETD 12: Measuring Equipment for Basic
Electrical Quantities]
“!ान $ एक न’ भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee””
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै”
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”

IS 1248 (Part 9) :2003

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Indian Standard
DIRECT ACTING INDICATING ANALOGUE
ELECTRICAL MEASURING INSTRUMENTS
AND THEIR ACCESSORIES
PART 9 TEST METHODS
Third Revision )
(
ICS 17.220.20

Cl BIS 2003
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002
December 2003 Price Group 9
McasurIng Equipment for Basic Electrical Quantities Sectional Committee, ET 12
FOREWORD
This lndian Standard (Part 9) (Third Revision) was adopted by the Bureau of Indian Standards, after the draft
finalizcd by the Measuring Equipment for Basic Electrical Quantities Sectional Committee had been approved
by the Electrotcchnical Division Council.
This standard covers the test methods.
TII]s standard was first published in 1958 and was revised in 1968 and in 1983. The third revision had been
undertaken to align it with IEC publication.
This standard isone of aseries ofnine Indian Standards on direct acting indicating analogue electrical measuring
instruments and their accessories. Other standards published in this series are as follows:
(Part 1):2003 Definitions and general requirements (@urbi revision)
(Part 2) :2003 Special requirements for ammeters and voltmeters (third revision)
(Part 3) :2003 Special requirements for wattmeters and varmeters (third revision)
(Part 4) :2003 Special requirements for frequency meters (third revision)
(Part 5) :2003 Special requirements for phase meters, power factor meters and synchroscopes
(third revision)
(Part 6) :2003 Special requirements for ohmmeters (impedance meters) and conductance meters
(third revision)
(Part 7) :2003 Special requirements for multi-function instruments (third revision)
(Part 8) :2003 Special requirements for accessories (third revision)
In preparation of this standard, assistance has been derived from IEC 60051-9 (1988) ‘Direct acting indicating
analoguc electrical measuring instruments and their accessories : Part 9 Recommended test methods’ fourth
edition, issued by the International Electrotechnical Commission (IEC).
For the purpose of deciding wh e ther a particular requirement of this standard is complied with the final value,
observed orcalculated, expressing t h eresult ofatestoranalysis, shallbe rounded off inaccordance with IS 2: 1960
{Rules for rounding off numerical values (revised)’. The number of significant places retained inthe rounded off
value should be the same as that of the specified value in this standard.
——-—,——-—— .—-—-—........,.—.—. ..___________
IS 1248 (Part 9) :2003
Indian Standard
DIRECT ACTING INDICATING ANALOGUE
ELECTRICAL MEASURING INSTRUMENTS
AND THEIR ACCESSORIES
PART 9 TEST METHODS
Third Revision )
(
1SCOPE vision should be such that the index tip is coincident
with its reflection in the mirror.
This standard (Part 9) specifies test methods for direct
acting indicating analogue electrical measuring NOTE —Care should be taken to avoid the effect of parallax
error when taking instrument readings.
instruments and their accessories.
3.3 Tapping
2 REFERENCES
Immediately prior to taking a reading, either the
2.1 The following Indian Standards are necessary instrument or itssupport shall be tapped lightly aswith
adjuncts to this standard: a finger or the eraser end of apencil.
Is No. Title However, tapping isnot permitted incertain tests such
as those for determining intrinsic error, return to zero
IS 1248 Direct acting indicating analogue
and the effects ofshock and vibration, asstated inthese
electrical measuring instruments and
test methods.
their accessories :
(Part 1):2003 General requirements (Jourt/z
3.4 Thermal Stability
revision)
All instruments shall be allowed to remain at the
(Part 3) :2003 Special requirements for wattmeters
reference temperature long enough to eliminate
and varmeters (third revision)
temperature gradients.
(Part 5) :2003 Special requirements for phase

meters, power fa ctor meters and NOTE —Two hours will usually besufficient,

synchroscopes (third revision)
3.5 Preconditioning Time
(Part 8): 2003 Special requirements foraccessories
(third revision) The provisions of 4.3.1 ofIS 1248 (Part 1)shall apply.
3 GENERAL TEST CONDITIONS 3.6 Zero Adjustment (Mechanical)
The test methods described inthis part shall be applied With the instrument disconnected from allsupplies and
under the following conditions unless otherwise before each set of readings istaken, the index shall be
specified. setonthezero scale mark ortoanappropriate reference
mark on the scale using the mechanical zero adjuster,
3.1 Reference Conditions
as follows:
Reference conditions shall be according to Table 1of
a) Operate the zero adjuster inadirection, which
the relevant parts of IS 1248. Where areference range
will drive the index toward the zero mark of
is specified, tests shall be performed at both limits of
the instrument.
the reference range.
b) While continuing to drive the index in the
3.2 Parallax direction selected in (a), set the index on the
zero mark while tapping the instrument case.
For an edgewise instrument, the line of vision should
Once the direction ofdrive has been selected,
be perpendicular to the instrument dial at the index
do not change ituntil the index ison the zero
tip.
mark.
For an instrument having a mirror scale, the line of c) With the index set on the zero mark, reverse
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1S1248 (Part 9) :2003
the direction of motion of the zero adjuster, If single-phase testing of polyphase instruments is
and drive it far enough to introduce permitted by the manufacturer, the current coils may
mechanical freedom (play) in the zero be connected in series and the voltage coils inparallel.
adjuster, but not far enough to disturb the In all cases, follow the manufacturer’s instructions for
position of the index. details ofconnections and the application ofcalibration
constants.
NOTE — Instruments without zero adjuster or where the
mechanical zero does not appear on scale shall not bereset.
3.11 a.c. Instrument Testing on d.c.
3.7 Zero Adjustment (Electrical)
Some a.c. instruments, for example electrodynamics,
Before each set of readings, the index shall be set on thermal or electrostatic instruments, may be tested
the reference mark with the electrical zero adjuster. on d.c. ifpermitted by the manufacturer. Ifthis isthe
Refer to the manufacturer’s instructions for details of case, perform the tests as specified for the instrument
this adjustment. but use a d.c. supply and neglect references to power
factor and phase angle. For these cases, the errors
3.8 Test Equipment Errors are computed from the average of the results from
testing with the reversal of polarity of each measuring
All tests shall be made using reference instruments
circuit. Other tests relating to ac variations may not
having an intrinsic error no more than one-fourth of
apply.
that corresponding to the accuracy class of the
instrument under test. However, the use of reference
3.12 Multirange and Multifunction Instruments
instrument having an intrinsic error no more than one-
tcnth of that corresponding to the accuracy class of All ranges and all functions shall be tested separately.
the instrument under test is strongly recommended. Instruments with multiple supply voltage capability
shall be tested separately on each supply connections.
When testing for variations; avoid, ifpossible, applying
the influence quantity (for example temperature) tothe 3.13 Test Leads
rcfcrcncc instrument. Otherwise, ensure that the
Iftest leads are specified by the manufacturer they shall
refer-cnce instrument isnot affected by more than one-
be used for these tests. Otherwise, the size and
fourth of the permissible variation of the instrument
placement of leads used in the performance of these
under test, where both are subjected to the same
tests shall be such that they do not influence the test
influcncc quantity (for example change offrequency).
results.
Manufacturers shall make allowance for reference
3.14 Ohmmeter Testing
instrument uncertainty to ensure that all instruments

arc within their error limits atthe time of shipment. In For high value test resistors, the insulation of the test

contrast, a user shall add the errors of his reference leads shall be adequate to ensure that the test resistor
instrument tothe permitted error when re-checking an isnot shunted to cause errors greater than one-tenth of
instrument and the resulting sum shall be used for the the rated intrinsic error of the ohmmeter.
limit for that test.
For low value resistors, the total resistance of the test
Nothing in these recommendations is intended to leads shall be allowed for, unless it is negligible in
prevent the use of special test methods and/or comparison with the value of the test resistor.
specialized test equipment for making testing simpler
Ohmmeters having special leads terminating inspikes
and/or more accurate.
may need special testresistors having terminals capable
3.9 Reading Methods of accepting the spikes.
Whenever possible, tests shall be conducted by setting Ohmmeters measuring the value of4-terminal resistors
the instrument under test to a scale mark and reading may need special test resistors.
the reference instrument.
Care shall be taken when testing high voltage
NOT[: —The reference instrument should have an adequate ohmmeters, that the voltage rating of the test resistor
scale resolution (or number ofdig{ts) toenable readings tobe isnot exceeded. This isnecessary both because of the
taken with aresolution atleast asgood asthat corresponding to
danger of insulation breakdown and because of the
one-fifth ofthe accuracy class ofthe instrument under test.
possibility of the test resistor having a significant
3.10 Polyphase Testing voltage coefficient.
Polyphase instruments maybe tested by connecting to Ifan ohmmeter has astated value of test voltage when
anappropriate polyphase supply withproperly me asured measuring a stated value of test resistance (or an open
and controlled voltages, currents and phase angles. circuit), the voltage should be measured using a
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IS 1248 (Part 9) :2003
voltmeter having a permissible error not exceeding marks (Bx) including the lower and upper
5 percent of the test voltage. Where the voltage is to limits ofthe measuring range without tapping.
be measured at a dctinite value of test resistance, Record the values of excitation (BR) as
the voltmeter may be shunted to obtain this value. shown by the reference instrument.
d) Increase the current to 120 percent of the
Care shall betaken that the test resistor isnot damaged
value corresponding to the upper limit of the
by the current supplied by the ohmmeter.
measuring range ortocause the index toreach
When an ohmmeter has a hand-driven generator, it the upper limit of itstravel, whichever isless.
should be turned, as nearly as possible, at a uniform Immediately and slowly reduce the current
speed and atthe speed stated by the manufacturer. Ifa to bring the index sequentially to the same
slipping clutch is provided, the turning speed should scale marks (Bx) as in (c) without tapping.
be about 10 percent higher than the clutch slipping Record the values of excitation (B,{)asshown
speed. by the reference instrument.
4 INTRINSIC ERROR TESTS NOTE —Forinstruments, inwhich thezero isdisplaced within
the scale, these tests should be performed on both sides ofthe
4.1 Ammeters and Voltmeters zero scale mark asappropriate.
4.1.1 Procedure 4.2.2 Computation
a) If relevant, set zero with tapping. The intrinsic error, expressed asapercentage, shall be
computed for each selected scale mark as follows:
b) Apply sufficient slowly, increasing excitation
to bring the index sequentially to each of at
(B)X– BR ~loo
least five approximately equidistant scale
marks (Bx) including the lower and upper A,
limits ofthe measuring range without tapping.
Record the values ofexcitation (B~)asshown 4.3 Frequency Meters (Pointer Type)
by the reference instrument.
4.3.1 Procedure
c) Increase the excitation to 120 percent of the
value corresponding to the upper limit of the a) If relevant, set index to reference mark with
measuring range ortocause the index toreach tapping.
the upper limit of its travel, whichever is the b) Apply rated voltage or avoltage atone ofthe
less. Immediately and slowly reduce the limits of the reference range at a low
excitation to bring the index sequentially to frequency and slowly increase the frequency

the same scale marks (Bx) as in (b) without to bring the index sequentially to each of at

tapping. Record the value s of excitation (B.) least five approximately equidistant scale
as shown by the reference instrument. marks (Bx) including the lower and upper
limits ofthe measuring range without tapping,
NOTE — For instrument inwhich the zero isdisplaced within
record the values of frequency (BR)as shown
the scale, these tests should beperformed on both sides ofthe
zero scale mark asappropriate. by the reference instrument.
4.1.2 Computation c) Increase the frequency to 120 percent of the
value corresponding to the upper limit of the
The intrinsic error, expressed as apercentage, shall be
measuring range ortocause the index toreach
computed for each selected scale markas follows:
the upper limit of its travel, whichever isthe
less. Immediately and slowly reduce the
(B)X-BR ~loo
frequency to bring the index sequentially to
A, the same scale marks (Bx) as (b) without
tapping.
4.2 Wattmeters and Varmeters Record the values offrequency (BR)asshown
by the reference instrument.
4.2.I Procedure
4.3.2 Computation
a) If relevant, set zero with tapping.
The intrinsic error, expressed as apercentage, shall be
b) Energize the voltage circuits atrated voltage
within ~ 2 percent. computed for each selected scale mark as follows :
c) Apply sufficient slowly increasing current to
(B)X– BR ~loo
bring the index sequentially to eac h of at
AF
least five approximately equidistant scale
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1S1248 (Part 9) :2003
4.4 Frequency Meters (Vibrating Reed Type) instruments which cannot indicate beyond
such limit. Immediately and slowly reduce
4.4.1 Procedure
the phase difference to bring the index
a) Apply rated voltage or avoltage atone of the sequentially to the same scale marks asin(d)
limits ofthe reference range atthe frequency without tapping. Record the values of phase
required to bring the reed with the highest difference (BR) as shown by the tapping
rating in that row (Bx) to resonate at its instrument.
greatest amplitude and record the value ofthe For phasemeters capable of continuous 360°
frequency (BR) as shown by the reference rotation, (d) shall be conducted inaclockwise
instrument. direction and shall then be repeated in a
b) Decrease the frequency tobring the reed with counterclockwise direction. (e) shall be
the next highest rating in that row (Bx) to omitted.
resonate at its greatest amplitude and record
4.5.2 Computation
the value of the frequency (BR)as shown by
the reference instrument. The intrinsic error, expressed asapercentage, shall be
c) Repeat (b) for each reed. computed for each selected scale mark as follows:
d) Repeat (a), (b) and (c) for each row ifthere is
(B)X-BR Xloo
more than one row.
A,
4.4.2 Computation
The intrinsic error, expressed as apercentage, shall be 4.6 Power Factor Meters
computed for each reed as follows:
4.6.1 Procedure
(B)x -B, a) If relevant, set zero with tapping.
Xloo
A, b) Connect the voltage circuit toavoltage source
complying with the requirements of Table 1
4.5 Phasemeters of IS 1248 (Part 1) and Table 1of IS 1248
(Part 5). Connect the current circuit to a
4.5.1 Procedure
separate source of current. Both sources shall
a) If relevant, set zero with tapping. besettothe same frequency. The phase angle
b) Connect one of the measuring circuits to a between the sources shall be adjustable and
source complying with the requirements of known.

Table 1of IS 1248 (Pa rt 1) and Table 1 of c) Apply 100 percent of rated current to the

IS 1248 (Part 5).Connect t he other measuring current circuit.
circuit toaseparate source. Both sources shall
d) Carefully and slowly increase the phase
bc settothe same frequency. The phase angle
difference to bring the index sequentially to
between the sources shall be adjustable and
at least five approximately equidistant scale
known.
marks (Bx) including the lower and upper
c) Slowly adjust the phase difference between limits of the measuring range, without
the two sources to zero and note the tapping. Record the values of power
indication. factor (BR) as shown by the reference
d) Carefully and slowly increase the phase instrument.
difference to bring the index sequentially e) Increase the phase difference to 120 percent
to each of at least five approximately of the value corresponding to the upper limit
equidistant scale marks (Bx) including the of the measuring range or to cause the index
lower and upper limits of the measuring toreach the upper limit ofitstravel, whichever
range without tapping. Record the values of isthe less, but only tothe value corresponding
phase difference (B~) as shown by the tothe upper limit of the measuring ranges for
rcfcrcnce instrument. instruments which cannot indicate beyond
c) Increase the phase difference to 120 percent such limit. Immediately and slowly reduce the
of the value corresponding to the upper limit phase difference to bring the index
of the measuring range or to cause the index sequentially tothe same scale marks asin (d)
toreach the upper limit ofitstravel, whichever without tapping. Record the values of phase
isthe Icss,but only tothe value corresponding difference (BR) as shown by the reference

tothe upper limit ofthe measuring ranges for instrument.
4
IS 1248 (Part 9) :2003
f) Repeat the test using 40 percent of rated Where possible, use an adjustable resistor (for example,
current in the current circuit. a multi-decade resistance box) as the test resistor and
adjust itto bring the index sequentially to each of the
For power factor meters capable of continuous 360°
numbered scale marks (Bx) without tapping. Record
rotation, (d)shall beconducted inaclockwise direction
the values of the test resistor (BR).
and then shall be repeated in a counterclockwise
direction. (e) shall be omitted. 4.8.2 Computation
4.6.2 Computation The intrinsic error, expressed as apercentage, shall be
computed for each selected scale mark as follows:
The intrinsic error, expressed asapercentage, shall be
computed for each selected scale mark as follows:
(B)x - BR
Xloo
(B), - BR A,
Xloo”
A,
4.9 Interchangeable Shunts
4.7 Synchroscopes 4.9.1 Procedure
4.7.1 Procedure a) Connect high current leads to the shunt of a
size suitable for the rated current using the
a) Connect both the incoming and the running
connection method intended by the
circuits to separate voltage sources equal to
manufacturer. If the shunt is intended for
the rated voltages for the instrument at rated
installation in a busbar, the test installation
frequency.
shall include a similar busbar configuration
b) Adjust the phase difference between the
with the shunt mounted in the intended
incoming and running circuits to bring the
position of use.
index to the synchronizing mark. Record the
phase difference (BD) as shown by the b) Apply rated current, orrated current adjusted
reference instrument. for the current drawn by the measuring
instrument, through the shunt and record the
NOTE — The incoming circuit isthat circuit which, inuse, is
voltage drop (B), as shown by the reference
normally connected toasource whose phase relative toanother
clrcui(. therunning circuit, istobeadjusted soastoenable them instrument. The rated current shall be d.c.
tobesynchronized. unless a frequency is stated. If the shunt may
be used on both ac and dc, separate tests shall
4.7.2 Computation

be performed.
The intrinsic error, expressed asape r centage, shall be
computed as follows: 4.9.2 Computation
The intrinsic error, expressed asapercentage, shall be
(B)
Q Xloo computed as follows:
A,
(B)-A, XIOO
4.8 Ohmmeters A,
4.8.1 Procedure
4.10 Interchangeable Series Resistors (Impedances)
a) The condition ofthe battery (ies), ifany, shall
be in accordance with the manufacturer’s 4.10.1 Procedure
statements.
a) Connect the resistor (impedance) in series
b) Ifrelevant, set mechanical zero with tapping.
with a suitable current measuring instrument
c) Carry out any preliminary adjustments that whose internal impedance is negligible
are specified by the manufacturer. compared with the resistor (impedance) under
d) Determine the error of the ohmmeter by test.
connecting it sequentially to known values b) Apply rated voltage across the resistor
of a test resistor. The uncertainty in the (impedance) in series with the current
knowledge of the values of the test resistor measuring instrument. Record the value ofthe
should be preferably one-tenth or less of the current (B), as shown by the reference
permissible error of the ohmmeter at that instrument. The rated voltage shall be d.c.
value. unless a frequency is stated. If the resistor
5