IEC 61298-2:2008

Process measurement and control devices - General methods and procedures for evaluating performance - Part 2: Tests under reference conditions

IEC 61298-2:2008 specifies general methods and procedures for conducting tests and reporting on the functional and performance characteristics of process measurement and control devices. The tests are applicable to any such devices characterized by their own specific input and output variables, and by the specific relationship (transfer function) between the inputs and outputs, and include analogue and digital devices. For devices that require special tests, this standard should be used, together with any product specific standard specifying special tests. It covers tests made under reference conditions.

Dispositifs de mesure et de commande de processus - Méthodes et procédures générales d'évaluation des performances - Partie 2: Essais dans les conditions de référence

La CEI 61298-2:2008 spécifie les méthodes et procédures générales pour l'exécution des essais portant sur les caractéristiques fonctionnelles et les caractéristiques de performance des dispositifs de mesure et de commande de processus. Ces essais sont applicables à tout dispositif à condition que ce dispositif soit caractérisé par ses propres grandeurs d'entrée et de sortie et par la relation spécifique (fonction de transfert) entre les entrées et les sorties. Ils concernent les dispositifs analogiques et numériques. Pour les dispositifs nécessitant des essais spéciaux, il convient que cette norme soit utilisée en conjonction avec la norme particulière de produit spécifiant ces essais spéciaux. Elle couvre les essais effectués dans les conditions de référence.

General Information

• Status: Published
• Publication Date: 07-Oct-2008
• ICS: 25.040.40 - Industrial process measurement and control
• Technical Committee: SC 65B - Measurement and control devices
• Drafting Committee: WG 6 - TC 65/SC 65B/WG 6
• Current Stage: PPUB - Publication issued
• Start Date: 08-Oct-2008
• Completion Date: 31-Oct-2008

Standards Content (Sample)

IEC 61298-2
Edition 2.0 2008-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Process measurement and control devices – General methods and procedures
for evaluating performance –
Part 2: Tests under reference conditions

Dispositifs de mesure et de commande de processus – Méthodes et procédures
générales d'évaluation des performances –
Partie 2: Essais dans les conditions de référence

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IEC 61298-2
Edition 2.0 2008-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Process measurement and control devices – General methods and procedures
for evaluating performance –
Part 2: Tests under reference conditions

Dispositifs de mesure et de commande de processus – Méthodes et procédures
générales d'évaluation des performances –
Partie 2: Essais dans les conditions de référence

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
U
CODE PRIX
ICS 25.040.40 ISBN 978-2-88910-484-0
– 2 – 61298-2 © IEC:2008
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
2 Normative references .7
3 Terms and definitions .7
4 Accuracy related factors .10
4.1 Test procedures and precautions .10
4.1.1 Selection of ranges for test.10
4.1.2 Preconditioning cycles.11
4.1.3 Number of measurement cycles and test points .11
4.1.4 Additional tests where digital inputs and outputs are provided .11
4.1.5 Measurement procedure .11
4.1.6 Processing of the measured values .12
4.1.7 Determination of accuracy related factors.12
4.1.8 Presentation of the results.16
4.2 Specific testing procedures and precautions for the determination of dead
band.16
4.2.1 Selection of ranges for test and preconditioning .16
4.2.2 Measurement procedure .16
4.2.3 Presentation of the results.17
5 Dynamic behaviour.17
5.1 General considerations.17
5.2 General testing procedures and precautions.17
5.3 Frequency response.17
5.4 Step response .18
6 Functional characteristic.18
6.1 General .18
6.2 Input resistance of an electrical device.18
6.3 Insulation of electrical devices.21
6.3.1 General considerations.21
6.3.2 Insulation resistance.21
6.3.3 Dielectric strength .22
6.4 Power consumption .22
6.4.1 Electrical power consumption .22
6.4.2 Air consumption.22
6.5 Output ripple of a device with an electrical d.c. output .23
6.6 Air flow characteristics of a pneumatic device .23
6.6.1 Initial setting up .23
6.6.2 Delivered flow Q .23
6.6.3 Exhausted flow Q .24
6.6.4 Data presentation .24
6.7 Limits of adjustments of lower range value and span.25
6.8 Switching differential .25
7 Drift .25
7.1 Start-up drift .25
7.2 Long-term drift.25

61298-2 © IEC:2008 – 3 –
Figure 1 – Error curves .15
Figure 2 – Two examples of frequency response .19
Figure 3 – Two examples of responses to a step input.20
Figure 4 – Test set-up for input resistance .21
Figure 5 – Test arrangement for measurement of airflow characteristics .23
Figure 6 – Typical air flow characteristics .24

Table 1 – Settings of span and lower range value adjustments .11
Table 2 – Number of measurement cycles and number and location of test points .12
Table 3 – Typical table of device errors .14
Table 4 – Dielectric strength test voltages .22

– 4 – 61298-2 © IEC:2008
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROCESS MEASUREMENT AND CONTROL DEVICES –
GENERAL METHODS AND PROCEDURES
FOR EVALUATING PERFORMANCE –
Part 2: Tests under reference conditions

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61298-2 has been prepared by subcommittee 65B: Devices and
process analysis, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This second edition cancels and replaces the first edition published in 1995 and constitutes a
technical revision.
This edition is a general revision with respect to the previous edition and does not include any
significant changes (see Introduction).

61298-2 © IEC:2008 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
65B/686/FDIS 65B/694/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 61298 series, under the general title Process measurement and
control devices – General methods and procedures for evaluating performance, can be found
on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – 61298-2 © IEC:2008
INTRODUCTION
This standard is not intended as a substitute for existing standards, but is rather intended as a
reference document for any future standards developed within the IEC or other standards
organizations, concerning the evaluation of process instrumentation. Any revision of existing
standards should take this standard into account.
This common standardized basis should be utilised for the preparation of future relevant
standards, as follows:
– any test method or procedure, already treated in this standard, should be specified and
described in the new standard by referring to the corresponding clause of this standard.
Consequently new editions of this standard are revised without any change in numbering
and scope of each clause;
– any particular method or procedure, not covered by this standard, should be developed
and specified in the new standard in accordance with the criteria, as far as they are
applicable, stated in this standard;
– any conceptual or significant deviation from the content of this standard, should be clearly
identified and justified if introduced in a new standard.

61298-2 © IEC:2008 – 7 –
PROCESS MEASUREMENT AND CONTROL DEVICES –
GENERAL METHODS AND PROCEDURES
FOR EVALUATING PERFORMANCE –
Part 2: Tests under reference conditions

1 Scope
This part of IEC 61298 specifies general methods and procedures for conducting tests and
reporting on the functional and performance characteristics of process measurement and
control devices. The tests are applicable to any such devices characterized by their own
specific input and output variables, and by the specific relationship (transfer function) between
the inputs and outputs, and include analogue and digital devices. For devices that require
special tests, this standard should be used, together with any product specific standard
specifying special tests.
This standard covers tests made under reference conditions.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60050-300, International Electrotechnical Vocabulary (IEV) – Electrical and electronic
measurements and measuring instruments (composed of Part 311, 312, 313 and 314)
IEC 60050-351, International Electrotechnical Vocabulary (IEV) – Part 351 : Control
technology
IEC 61298-1, Process measurement and control devices – General methods and procedures
for evaluating performance – Part 1: General considerations
IEC 61010-1, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 1: General requirements
3 Terms and definitions
For the purpose of this document, the following relevant terms and definitions, some of them
based on IEC 60050(300) or IEC 60050(351), apply.
3.1
variable
quantity or condition whose value is subject to change and can usually be measured (e.g.,
temperature, flow rate, speed, signal, etc.)
[IEV 351-21-01, modified]
3.2
signal
physical quantity, one or more parameters of which carry information about one or more
variables which the signal represents
[IEV 351-21-51, modified]
– 8 – 61298-2 © IEC:2008
3.3
range
range of values defined by the two extreme values within which a variable can be measured
within the specified accuracy
[IEV 351-27-11, modified]
3.4
span
algebraic difference between the values of the upper and lower limits of the measuring range
[IEV 311-03-13]
3.5
inaccuracy
maximum positive and negative deviation from the specified characteristic curve observed in
testing a device under specified conditions and by a specified procedure
NOTE 1 Accuracy is defined in IEC 60050-300, definition 311-06-08.
NOTE 2 The term inaccuracy is sometime referred to as measured accuracy. This term should not be used.
3.6
error
algebraic difference between the indicated value and a comparison value of the measured
variable
[IEV 351-27-04, modified]
NOTE The error is positive when the indicated value is greater than the comparison value. The error is generally
expressed as a percentage of the relevant ideal span.
3.7
measured error
largest positive or negative value of errors of the average upscale or downscale values at
each point of measurement
3.8
non-conformity
the closeness with which a calibration curve approximates to a specified characteristic curve
(which can be linear, logarithmic, parabolic, etc.)
NOTE Non-conformity does not include hysteresis.
3.9
non-linearity
deviation from linearity
NOTE 1 Linearity is defined in IEC 60050(300), definition 311-06-05.
NOTE 2 Non-linearity does not include hysteresis.
3.10
non-repeatability
deviation from repeatability
NOTE Repeatability is defined in IEC 60050(300), definition 311-06-06.
3.11
hysteresis
property of a device or instrument whereby it gives different output values in relation to its
input values depending on the directional sequence in which the input values have been
applied
[IEV 351-24-15, modified]
61298-2 © IEC:2008 – 9 –
3.12
dead band
finite range of values within which a variation of the input variable does not produce any
measurable change in the output variable
[IEV 351-24-14, modified]
3.13
dead-time
time interval between the instant when a variation of an input variable is produced, and the
instant when the subsequent variation of the output variable starts
[IEV 351-28-41]
(see IEC 60050-351, Figure 5)
3.14
rise time
for a step response, the duration of the time interval between the instant when the output
variable (starting from zero) reaches a small specified percentage (for instance 10 %) of the
final steady-state value, and the instant when it reaches for the first time a large specified
percentage (for instance 90 %) of the same difference
[IEV 394-39-11, modified]
(see IEC 60050-351, Figure 3)
3.15
settling time
time interval between the instant of the step change of an input variable, and the instant when
the output variable does not deviate by more than a specified tolerance from its final steady
state value (see IEC 60050-351, Figure 3). For this standard, a tolerance of 1 % is adopted
[IEV 351-24-29]
3.16
step response time
time interval between the instant of a step change in the input variable and the instant when
the output variable reaches for the first time a specified percentage of the difference between
the final and the initial steady state value (see IEC 60050-351, Figure 3). For this standard , a
specified percentage of 90 % is adopted
[IEV 351-24-28]
3.17
time constant
time required to complete 63,2 % of the total change of the output of a first-order linear
system, produced by a step variation of the input variable
[IEV 351-24-24]
3.18
test procedure
statement of the tests to be carried out, and the conditions for each test, agreed between the
manufacturer, the test laboratory, and the purchaser/user before the evaluation starts
3.19
type tests
a test of one or more devices made to a certain design to show that the design meets certain
specifications
NOTE The type tests are in principle applied only on a sample. Normally are not repeated on all the individual
units of equipment made in series.

– 10 – 61298-2 © IEC:2008
3.20
performance evaluation
a complete test to establish the performance of a device under any likely operating conditions
to permit comparison with the manufacturer’s published or stated performance specification
for the device, or the user’s requirements
3.21
routine test
a simplified test to which each individual instrument is subjected during or after manufacture
to ascertain whether it complies with certain criteria
3.22
sample test
a simplified test to check specific characteristics of a device
4 Accuracy related factors
4.1 Test procedures and precautions
4.1.1 Selection of ranges for test
Where there are switched ranges or dial settings (e.g., gain), the tests shall be repeated to
cover all ranges or settings. When the Device Under Test (DUT) is supplied calibrated for use,
the first set of tests shall be carried out without adjustment.
4.1.1.1 Criteria
The measurements shall be performed with the devices operating at the minimum number of
calibration settings necessary to establish the device performance in all required operational
settings required by the test programme (see Clause 5 of IEC 61298-1).
Testing of a device which has provision for substantial adjustment of both span and lower
range value may require an impractically large number of tests. In such a case, preliminary
tests shall be conducted to determine the effect of changing span and lower range value
adjustments on the characteristic being measured. This should enable some tests to be
eliminated from the test programme in cases where the characteristic can be inferred reliably
from fewer tests. For example, hysteresis may not be significantly affected by selection of the
lower and upper range value if the span is held constant, and often may be inferred for
different spans from measurements at a single span setting.
However, the report shall indicate clearly relevant values of the measured parameters for
each setting of the adjustments, so that the values of inaccuracy, hysteresis, etc, can all be
referenced to the same adjustment of the device.
4.1.1.2 Setting of span and lower range value adjustments
Generally, unless otherwise specified in the test programme, the test for accuracy related
factors shall be carried out with the adjustments set at the settings A, B, C, D, listed below,
and in accordance with Table 1 whenever the span and/or the lower range value adjustments
are adjustable further than the adjustments for the manufacturing tolerances.
NOTE For tests of dynamic behaviour, functional characteristics, and drift, refer to the appropriate clauses of this
standard.
61298-2 © IEC:2008 – 11 –
Table 1 – Settings of span and lower range value adjustments
Zero suppression
Kind of test Adjustable span
and/or elevation
Complete Performance evaluation
A B
Tests Type test
Simplified Routine tests
C D
Tests Sample test
Setting A – Span adjustment set at the maximum and minimum values specified by the
manufacturer, and at one intermediate value.
Setting B – Normally, tests will be done at only one setting of lower range value, without
suppression or elevation, but further tests at minimum and maximum settings
may be required if the effects are significant.
Setting C – Unless otherwise specified in the test programme, the span shall be as set by
the manufacturer.
Setting D – Unless otherwise specified in the test programme, the lower range value shall
be as set by the manufacturer.
4.1.2 Preconditioning cycles
Prior to recording observations, the DUT shall be preconditioned (see 7.12 of IEC 61298-1)
and shall be exercised by three full range traverses in each direction.
4.1.3 Number of measurement cycles and test points
The performance of the DUT shall be verified over the full range for increasing and
decreasing values.
Taking into account the economic aspects outlined in 5.2 of IEC 61298-1, the number of
measurement cycles and of test points shall be the lowest possible. The number and location
of the test points shall be consistent with the kind of test, the degree of accuracy desired, and
the characteristic being evaluated.
The number of increasing and decreasing test points shall be the same for each pre-
determined test point, with the exception of 0 % and 100 %, that are reached only when going
downscale or upscale.
The number of measurement cycles and the number of the test points depend on the kind of
test under consideration. Unless otherwise specified for a particular type of device, the values
and locations that should be adopted are given in Table 2.
4.1.4 Additional tests where digital inputs and outputs are provided
Tests shall be made to ensure that the protocols comply with international standards (e.g., RS
232, IEEE 488) or the protocols fully specified by the DUT supplier. Tests shall be carried out
to confirm that the DUT functions correctly to the specified protocol under reference
conditions, and without error (or within any error rate specified by the supplier). The levels of
logical "1" and "0" shall be determined. Appropriate tests shall also be made for display errors
(missing digit sections, etc.), brightness, contrast, and angle of view before loss of
brightness/contrast. The update rate shall be recorded, together with display (accuracy)
errors.
4.1.5 Measurement procedure
The first measurement shall be performed to the first significant value of the scale after 0 % of
input span (e.g., 10 % of input span – see Table 2).

– 12 – 61298-2 © IEC:2008
Initially, an input signal equal to the lower range value is generated, and then the input signal
is slowly increased to reach, without overshoot, the first test point; after an adequate
stabilization period, the value of the corresponding input and output signal is noted.
Then the input signal is slowly increased to reach, without overshoot, the value of the next
test point and, after a stabilization period, the corresponding value of the output signal is
recorded.
The operation is repeated for all the predetermined values up to 100 % of the input span.
After measurement at this point, the input signal is slowly brought down to the test value
directly below 100 % of input span, and then to all the other values in turn down to 0 % of
input span, thus closing the measurement cycle.
Table 2 – Number of measurement cycles and number and location of test points
Number of Location of
Number
Kind of test measurement test points
of test points
cycles (% of input span)
Complete Performance 6 0-20-40-60-80-100
evaluation
3 or 5
Tests Type tests 11 0-10-20-30-40-50-60-70-80-90-100
Simplified Routine tests 1 5 0-25-50-75-100
Tests Sample tests
4.1.6 Processing of the measured values
The difference between the output signal values obtained at the various test points for each
upscale and downscale traverse and the corresponding ideal values are recorded as the
output errors.
The errors generally shall be expressed as percent of the ideal output span. On certain
devices (e.g., recorders, or devices with adjustable gain), it may be more convenient to
express the errors as percent of nominal input span (see 7.16 of IEC 61298-1).
For each measuring point, the readings obtained in successive cycles for upscale and
downscale error, respectively, shall be averaged to give average upscale and downscale
values, and these averaged to give the average value at that point.
All the error values thus obtained shall be shown in a table (see Table 3), and the average
values shall be presented graphically (see Figure 1).
4.1.7 Determination of accuracy related factors
Because of the limited number of measurements (see 4.1.3), the accuracy related factors
shall be determined by treating the errors in a mathematically simple way, and not on the
basis of statistical methods. The different methods of treatment are described in the following
clauses.
4.1.7.1 Inaccuracy
Inaccuracy is determined from Table 3 by selecting the greatest positive and negative
deviations of any measured value from the ideal value for increasing and decreasing inputs
for any test cycle separately, and reporting this in percent of ideal output span.

61298-2 © IEC:2008 – 13 –
4.1.7.2 Maximum measured error
Maximum measured error is determined from table 3 by selecting the greatest positive or
negative value from the average upscale errors and the average downscale errors.
4.1.7.3 Non-linearity
For devices that have a linear input/output relationship, the non-linearity is determined from
the curve plotted using the overall average of corresponding upscale and downscale average
errors (see Table 3 and Figure 1).
The maximum positive or negative deviation between the average curve and the selected
straight line, expressed in percent of ideal output span, is the non-linearity, and is
independent of dead band and hysteresis.
a) Terminal based non-linearity
Terminal based non-linearity is determined by drawing a straight line so that it coincides
with the average calibration curve at the upper range value and at the lower range value.
NOTE Where calibrations in workshops and adjustments in the field are made, only terminal based non-
linearity is of practical interest. Other expressions of non-linearity are sometimes used.
b) Independent non-linearity
Independent non-linearity is determined by drawing a straight line through the average
curve in such a way as to minimize the maximum deviation. It is not necessary that the
straight line be horizontal, or pass through the end points of the average calibration curve.
c) Zero based non-linearity
Zero based non-linearity is determined by drawing a straight line so that it coincides with
the average calibration curve at the lower range value (zero), and minimizes the maximum
deviation.
– 14 – 61298-2 © IEC:2008
Table 3 – Typical table of device errors

Average of
Total
st nd rd
1 cycle 2 cycle 3 cycle
the cycles
average
Error (in % of ideal span)
Up Down Up Down Up Down Up Down Average
Input
actual actual actual actual actual actual actual average error
in %
span
% % % % % % % %
%
0 –0,04 –0,05 +0,06 –0,05 –0,050
10 +0,06 +0,14 +0,04 +0,15 +0,05 +0,16 +0,05 +0,15 +0,100
+0,26 +0,175
+0,13 +0,23 +0,08 +0,09 +0,26 +0,10 +0,25
+0,11 +0,24 +0,26 +0,10 +0,25
30 +0,09 +0,25 +0,10 +0,175
+0,17
40 –0,04 +0,13 –0,07 +0,15 –0,04 –0,05 +0,15 +0,050
–0,075
50 –0,18 –0,02 –0,16 +0,01 –0,13 +0,01 –0,15 0,00
–0,27 –0,25 –0,23 –0,08 –0,025 –0,10 –0,175
60 –0,12 –0,10
–0,28 –0,30 –0,15 –0,225
–0,32 –0,17 –0,30 –0,16 –0,12
80 –0,27 –0,17 –0,26 –0,15 –0,22 –0,13 –0,25 –0,15 –0,200
–0,15 –0,05 –0,14
90 –0,16 –0,06 –0,04 –0,15 –0,05 –0,100
100 +0,09 +0,10 +0,10 +0,100
+0,11
Non-repeatability = +0,05 %
Hysteresis = +0,22 %
= hysteresis error + dead band
Maximum measured error = –0,30 %
Inaccuracy = –0,32 % +0,26 %
61298-2 © IEC:2008 – 15 –
0,3
Downscale average
0,2 Average
0,1
Terminal based straight line
Zero based straight line
Independent straight line
–0,1
Upscale average
–0,2
–0,3
0 10 20 30 40 50 60 70 80 90 100
Percent input span
Independent non-linearity = ± 0,2 %
2 Terminal based non-linearity = – 0,28 % and at ± 0,28 %
3 Zero based non-linearity = ± 0,22 %
IEC  1711/08
Figure 1 – Error curves
4.1.7.4 Non-conformity
The term non-conformity (terminal based non-conformity, independent non-conformity, and
zero based non-conformity) should be used for devices which have a non-linear input-output
relationship (e.g., logarithmic, square root, etc.).
The non-conformity is determined and presented using the same procedures as for non-
linearity.
4.1.7.5 Hysteresis
Hysteresis is determined directly from the deviation values shown in Table 3, and it is the
difference between consecutive upscale and downscale outputs for any single test cycle at
the same test point.
The maximum value observed from all the test cycles is reported as ”hysteresis”, and shall be
expressed as percent of the ideal output span. If required, hysteresis error may be determined
by subtracting the value of dead band from the corresponding value of hysteresis for a given
measured point; its maximum value may be reported, as “hysteresis error”, in percent of the
ideal output span.
Average error, percent of ideal output span

– 16 – 61298-2 © IEC:2008
NOTE Dead band may be determined by a conventional dead band test as described in 4.2.2.
4.1.7.6 Non-repeatability
The non-repeatability is the algebraic difference between the extreme values obtained by a
number of consecutive measurements of the output over a short period of time, for the same
value of the input, under the same operating conditions, approaching from the same direction,
for full range traverses.
Non-repeatability is usually expressed in percentage of ideal output span, and does not
include hysteresis.
Non-repeatability is determined directly from Table 3. Observe the maximum difference in
percent of the ideal output span, between all values of output for any single input value,
considering upscale and downscale curves separately. The maximum value from either
upscale or downscale value is reported as non-repeatability.
4.1.8 Presentation of the results
The results of measurements made during the tests shall be presented in the report by
including figures corresponding to Table 3 and Figure 1. These figures shall be included in the
test report.
The values of inaccuracy, or measured error, or non-conformity, hysteresis, and non-
repeatability shall be determined in accordance with 4.1.7, and tabulated in the test report.
The corresponding values of the accuracy related factors specified by the manufacturer shall
be tabulated alongside the values determined from the tests.
Note that the accuracy related terms may be stated by the manufacturer either as:
– the inaccuracy (which includes hysteresis and non-repeatability) and the hysteresis; or
– the measured error (which includes hysteresis) and the hysteresis; or
– the non-linearity/non-conformity (which does not include hysteresis), the hysteresis and
the dead band.
4.2 Specific testing procedures and precautions for the determination of dead band
4.2.1 Selection of ranges for test and preconditioning
Dead band is measured by using the same ranges and preconditioning as for the deter-
mination of accuracy related factors in 4.1.1 (Table 1) and 4.1.2.
4.2.2 Measurement procedure
Unless the dead band is known to be insignificant, it shall be measured as follows. Dead band
shall be measured three times at each of three test points at 10 %, 50 % and 90 % of span,
by proceeding as follows:
a) slowly increase the input variable to the DUT until a detectable output change is observed;
b) note the input value;
c) slowly decrease the input until a detectable output change is observed;
d) note the input value.
It shall be necessary to observe and record the output values at least three times, and
preferably five times, over full range traverses in each direction. The increment through which
the input signal is varied (difference between b) and d) above) is the dead band at this point.

61298-2 © IEC:2008 – 17 –
4.2.3 Presentation of the results
The maximum value of dead band at each test point, shall be tabulated, in percent of ideal
input span, in the test report.
The maximum overall value shall be reported as the dead band of the DUT.
If the dead band value is specified by the manufacturer, this value shall be reported beside
the value determined in the test.
5 Dynamic behaviour
5.1 General considerations
The objective of this part of the standard is to give data that will characterize dynamic
performance of the DUTs in a uniform, comparable manner.
For the purposes of this standard, sine wave and step input signals may be used for dynamic
response tests, as required.
Sine wave test data are most generally useful for mathematical analysis, for graphical solution
of control problems, and for characterization of dynamic performance of linear systems.
Step tests permit the measurement of the dead time, and give a qualitative evaluation of the
non-linearity of the DUT.
In order to arrive at a practical number of tests, in accordance with 5.2 of IEC 61298-1, for the
majority of equipment, only one value of output load and a minimum number of input signal
configurations need be adopted.
It is realized that the data from the specified step and sine wave tests will not suffice to
describe completely non-linearities of the DUT. However, this standard is intended to give
comparable data useful to identify the dynamic behaviour of simple devices, and to give
qualitative indications for the more complex ones. In special cases, more detailed testing may
be specified in the test programme.
NOTE The specified output loads and the levels of input signals are sufficient to give valid data for the most usual
test requirements, and qualitative indications on the effect of unusual large, changing signals.
5.2 General testing procedures and precautions
Testing shall be carried out with the span adjusted to the approximate mean of the maximum
and minimum span, and with the lower range value set approximately at the mid-point of its
permissible range of adjustment.
If there are adjustable functions (e.g., filters, dampers) provided to modify the dynamic
behaviour of the DUT, tests shall be carried out with these adjustments set to have first their
minimum and then, if required, their maximum effects.
For tests to assess the dynamic behaviour of devices with an electrical output, a realistic load
on the electrical output may be simulated by the connection of a 0,1 μF capacitor across the
resistive load, unless some other value is specified in the test programme.
5.3 Frequency response
A sinusoidal signal shall be applied by a function generator to the input of the DUT.

– 18 – 61298-2 © IEC:2008
The peak-to-peak amplitude of the sinusoidal signal should not exceed 20 % of span, but
shall be sufficient to allow a valid measurement without causing distortion or saturation of the
output.
The frequency of the input signal shall be increased in increments, from an initial value low
enough to determine the static gain, to a higher frequency at which the output is attenuated to
less than 10 % of its initial amplitude, or at which the phase lag will be 300°.
At least one complete cycle of the input and output shall be recorded simultaneously at each
frequency step.
The results of these tests shall be presented graphically in the following form (see Figure 2):
– the gain and the phase lag shall be plotted against frequency on a logarithmic scale.
From the graphs, the following values shall be obtained:
a) the frequency at which the relative gain is 0,7;
b) the frequency at which the phase lag is 45°;
c) the frequency at which the phase lag is 90°;
d) the maximum relative gain, and the corresponding frequency and phase angle.
5.4 Step response
A series of step changes shall be applied to the input of the DUT. The rise time of the step
input shall be small compared with response time of the DUT.
Input step and output response shall be recorded together.
The following input steps shall be applied:
– a step corresponding to 80 % of output span, giving an output change from 10 % to 90 %,
then another from 90 % to 10 %;
– steps, corresponding to 10 % output span, giving output changes up and down as follows:
5 % to 15 %; 45
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