IEC 60546-1:2010

IEC 60546-1 ®
Edition 3.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Controllers with analogue signals for use in industrial-process control systems –
Part 1: Methods of evaluating the performance

Régulateurs à signaux analogiques utilisés pour les systèmes de conduite des
processus industriels –
Partie 1: Méthodes d’évaluation des performances

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IEC 60546-1 ®
Edition 3.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Controllers with analogue signals for use in industrial-process control systems –
Part 1: Methods of evaluating the performance

Régulateurs à signaux analogiques utilisés pour les systèmes de conduite des
processus industriels –
Partie 1: Méthodes d’évaluation des performances

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
W
CODE PRIX
ICS 25.040.40 ISBN 978-2-88912-139-7
– 2 – 60546-1 © IEC:2010
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.8
2 Normative references .8
3 Terms and definitions .9
4 Basic relationships .10
4.1 Input/output relations of idealized controllers.10
4.2 Limitations.12
4.3 Dial graduation of controllers.12
5 General test conditions.13
5.1 Environmental conditions .13
5.1.1 Recommended range of ambient conditions for test measurements .13
5.1.2 Standard reference atmosphere.13
5.1.3 Standard atmosphere for referee measurements .13
5.2 Supply conditions .14
5.2.1 Reference values.14
5.2.2 Tolerances .14
5.3 Load impedance.14
5.4 Other test conditions .14
5.5 Stabilizing the controller output .15
6 Offset .16
6.1 Test set-up.16
6.2 Initial conditions .16
6.3 Test procedure .16
6.3.1 Offset at different values of X .16
p
6.3.2 Effect of changes of reset and rate time .17
7 Dial markings and scale values .17
7.1 Verification of set point scales.17
7.2 Proportional action .17
7.2.1 Initial conditions .17
7.2.2 Test procedure .17
7.2.3 Dead band.18
7.3 Integral action .19
7.3.1 Initial conditions .19
7.3.2 Test procedure .19
7.4 Derivative action .21
7.4.1 Initial conditions .21
7.4.2 Test procedure .21
8 Effect of influence quantities.22
8.1 General .22
8.2 Initial conditions .22
8.3 Climatic influences .23
8.3.1 Ambient temperature (as per IEC 61298-3).23
8.3.2 Humidity (electric controllers only) (as per IEC 61298-3) .23
8.4 Mechanical influences .23
8.4.1 Mounting position .23

60546-1 © IEC:2010 – 3 –
8.4.2 Shock .23
8.4.3 Mechanical vibration.24
8.5 Power supply influences.25
8.5.1 Power supply variations.25
8.6 Electrical interferences.26
8.6.1 Common mode interference (see Figure 7) .26
8.6.2 Series mode interference.27
8.6.3 Earthing.28
8.6.4 Radio interference .28
8.6.5 Magnetic field interference .28
8.6.6 Electrostatic discharge .29
8.7 Output load (electric controllers only) .29
8.8 Accelerated operational life test .29
8.8.1 Initial conditions .29
8.8.2 Test procedure .30
9 Output characteristics and power consumption .30
9.1 Consumed and delivered energy .30
9.1.1 General .30
9.1.2 Initial conditions .30
9.1.3 Air flow delivered or exhausted (pneumatic controllers) .30
9.1.4 Steady-state air consumption (pneumatic controllers) .31
9.1.5 Power consumption (electric controllers) .31
9.2 "Automatic"/"Manual" transfer.31
9.3 Ripple content of electrical output .31
10 Frequency response .31
10.1 Application of frequency response tests .31
10.2 Test procedure .32
10.3 Analysis of test results .32
11 Miscellaneous tests .32
11.1 Voltage test (see also IEC 61010-1) .32
11.2 Insulation resistance (see also IEC 61010-1).33
11.3 Input over-range.33
12 Documentary information.33
13 Technical examination.34
14 Test report.34
15 Summary of tests .34
Bibliography.38

Figure 1 – Basic signals to/from an idealized controller.10
Figure 2a – Arrangement for open loop or closed loop tests.15
Figure 2b – Arrangement for measuring air flow.16
Figure 3 – Characteristics of a controller with proportional action only .19
Figure 4 – Recorded characteristics of proportional action .20
Figure 5 – Recorded characteristics of integral action.21
Figure 6 – Recorded characteristics of derivative action .22
Figure 7 – Arrangement for common mode interference test (a.c. generator) .27
Figure 8a – Arrangement for series mode interference test (voltage input).28

– 4 – 60546-1 © IEC:2010
Figure 8b – Arrangement for series mode interference test (current input) .29
Figure 9 – Flow characteristic of a pneumatic controller.31
Figure 10 – Frequency response test results.37

Table 1 – Operating conditions for mechanical vibration tests .24
Table 2 – Conditions for frequency response tests.32
Table 3 – Voltage test values.33

60546-1 © IEC:2010 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CONTROLLERS WITH ANALOGUE SIGNALS FOR USE IN
INDUSTRIAL-PROCESS CONTROL SYSTEMS –

Part 1: Methods of evaluating the performance

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
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 60546-1 has been prepared by subcommittee 65B: Devices and
process analysis, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This third edition cancels and replaces the second edition, published in 1987. This third
edition constitutes a minor technical revision made to bring terms, measurement units and
references up to date.
The text of this standard is based on the following documents:
CDV Report on voting
65B/659A/CDV 65B/717A/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.

– 6 – 60546-1 © IEC:2010
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 60546 series, under the general title: Controllers with analogue
signals for use in industrial-process control systems, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.
60546-1 © IEC:2010 – 7 –
INTRODUCTION
The methods of evaluation given in this International Standard are intended for use by
manufacturers to determine the performance of their products and by users, or independent
testing establishments, to verify manufacturers’ performance specifications.
Part 2 of IEC 60546 describes a limited series of tests which may be used as acceptance
tests.
The tests specified in this standard are not necessarily sufficient for instruments specifically
designed for unusually arduous duties. Conversely, a restricted series of tests may be
suitable for instruments designed to perform within a limited range of conditions.
It will be appreciated that the closest liaison should be maintained between an evaluating
body and the manufacturer. Note is taken of the manufacturer’s specifications for the
instrument when the test program is being decided, and the manufacturer should be invited to
comment on both the test program and the results. His comments on the results should be
included in any report produced by the testing organization.

– 8 – 60546-1 © IEC:2010
CONTROLLERS WITH ANALOGUE SIGNALS FOR USE IN
INDUSTRIAL-PROCESS CONTROL SYSTEMS –

Part 1: Methods of evaluating the performance

1 Scope
This International Standard applies to proportional-integral-derivative (PID) pneumatic and
electric industrial-process controllers using analogue continuous input and output signals
which are in accordance with current international standards.
It should be noted that while the tests specified herein cover controllers having such signals,
they can be applied in principle to controllers having different but continuous signals. It should
be also noted that this standard has been written for pneumatic and electric industrial-process
controllers with only analogue components and is not necessarily to be used for controllers
with microprocessors.
This standard is intended to specify uniform methods of test for evaluating the performance of
)
industrial-process PID controllers with analogue input and output signals .
The test conditions specified in this standard, for example the range of ambient temperatures,
power supply, etc., are used when no other values are agreed upon by the manufacturer and
the user.
When a full evaluation in accordance with this standard is not required, those tests which are
required shall be performed and the results reported in accordance with those parts of the
standard which are relevant. The testing program should be subject to an agreement between
manufacturer and user, depending on the nature and the extent of the equipment under
consideration.
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 60068-2-6, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-30, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic (12 h + 12 h
cycle
IEC 60068-2-31, Environmental testing – Part 2-31: Tests – Test Ec: Rough handling shocks,
primarily for equipment-type specimens
IEC 61000-4-2, Electromagnetic compatibility (EMC) – Part 4-2: Testing and measurement
techniques – Electrostatic discharge immunity test
IEC 61000-4-3, Electromagnetic compatibility (EMC) – Part 4-3: Testing and measurement
techniques – Radiated, radio-frequency, electromagnetic field immunity test
—————————
)
See IEC 60381 and IEC 60382.
60546-1 © IEC:2010 – 9 –
IEC 61010-1, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 1: General requirements
IEC 61298-1, Process measurement and control devices – General methods and procedures
for evaluating performance – Part 1: General considerations
IEC 61298-3, Process measurement and control devices – General methods and procedures
for evaluating performance – Part 3: Tests for the effects of influence quantities
IEC 61298-4, Process measurement and control devices – General methods and procedures
for evaluating performance – Part 4: Evaluation report content
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
proportional band
proportional band X of a linear controller, expressed in per cent, given by the expression:
p
X = (1)
p
K
p
3.2
direct acting
controller output, which increases with an increase in the measured value
3.3
reverse acting
controller output, which decreases with an increase in the measured value
3.4
offset
steady-state deviation between measured value and set point
3.5
controller, proportional
P
controller which produces proportional control action only
3.6
controller, proportional plus derivative (rate)
PD
controller which produces proportional plus derivative control action
3.7
controller, proportional plus integral (reset)
PI
controller which produces proportional plus integral control action
3.8
controller PID
controller with compound action which produces proportional, plus integral, plus derivative
actions
– 10 – 60546-1 © IEC:2010
3.9
dead band
finite range of values within which variation of the input variable does not produce any
measurable change in the output variable
3.10
average upscale error
arithmetic mean of the errors at each point of measurement for the upscale readings of each
measurement cycle
3.11
average downscale error
arithmetic mean of the errors at each point of measurement for the downscale readings of
each measurement cycle
3.12
average error
arithmetic mean of all upscale and downscale errors at each point of measurement
3.13
hysteresis
difference between the average upscale error and the average downscale error at each point
of measurement
4 Basic relationships
4.1 Input/output relations of idealized controllers
In its simplest form, the relationship may be given by an equation generally presented in one
of the following forms:
Controller
x – w
w PID y
IEC  1620/10
x
Figure 1 – Basic signals to/from an idealized controller

60546-1 © IEC:2010 – 11 –
t
()
d x − w
(2)
y − y = K()x − w + K (x − w)dt + K
0 p I D
∫
dt
t
⎡ ⎤
1 d()x − w
⎢ ⎥
y − y = K ()x − w + ()x − w dt + T (3)
0 p D
∫
⎢ T dt ⎥
I
⎣ ⎦
or in the frequency domain:
⎡ ⎤
F()jω = K 1+ + jω T (4)
p ⎢ ⎥ D
jω T
⎣ I ⎦
These equations are valid for controllers with no interaction between factors K , K and K .
p 1 D
The equation for idealized controllers with interaction taken into account may be written as:
t
⎡ ⎤
1 T ′ d()x − w
D
⎢ ⎥
′
y − y = K A ()x − w + ()x − w dt + (5)
0 p
∫
′
⎢ A T A dt ⎥
I
⎣ 0 ⎦
In this equation, A is the interaction factor that depends on the structure of the controller. It
can often be written as:
K
T ′
p
D
′
A = 1+   (6a);   K =          (6b)
p
A
T ′
I
T
′ ′
T = 1+   (6c);         T = A T          (6d)
D D
I
A
where
t is the time;
y is the output signal (correcting variable);
y is the output signal at time t = 0 (controller output balance);
x is the measured value (controlled variable);
w is the set point value (reference input variable);
K is the proportional action factor (proportional action coefficient (see Note 1);
p
K is the integral action factor (integral action coefficient (see Note 1);
K is the derivative action factor (derivative action coefficient (see Note 1);
D
T is the reset time;
I
T is the rate time;
D
x and w, and consequently also y can be functions of time t, and:
e is the error or controller off-set, i.e.: x – w;
ω is the angular velocity.
NOTE 1 For the definition of this term, see IEC 60050-351.
NOTE 2 This standard is limited to P, PI, PD or PID controllers.
NOTE 3 The factors K , K and K may have the sign “plus” or “minus”; it is usual to associate “direct action” with
p 1 D
the positive sign and “reverse action” with the negative sign.
NOTE 4 Symbols with prime (K′ , T′ T′ ) represent nominal values, in contrast to effective values.
p I D
NOTE 5 Integral-action time constant and derivative-action time constant refer only to pure integral or derivative-
action controllers (IEC 60050-351)).

– 12 – 60546-1 © IEC:2010
There are controllers with still other structures, for example where the differentiation is
applied only to the measured value x, not to (x – w).
Equation (5) therefore becomes:
t
⎡ ⎤
T ′
1 d
D
⎢ ⎥
′
y − y = K A ()x − w + ()x − w dt + ()x (7)
0 p
∫
′
⎢ A T A dt ⎥
I
⎣ 0 ⎦
4.2 Limitations
The equations describing the performance of an actual controller are usually different from
equations (2) to (7) because they include time constants and limitations.
Two commonly encountered deviations from the idealized controller equations can be
expressed as follows:
a) Maximum integral gain V
I
Because of the finite integral gain of actual controllers, the integral part of equations (2)
and (3) is an approximation of the actual response only for sufficiently high frequencies.
For low frequencies, a controller may have an integral action [integral term of equation (4)]
expressed in the frequency domain as follows:
V
I
F()jω = K (8)
p
1+ jω T V
I 1
b) Maximum derivative gain V
D
Because of the limited derivative gain of actual controllers, the derivative terms of
equations (2) and (3) are an approximation of the actual response only for sufficiently low
frequencies. In the most simple case, there may be additional time constant and
proportional terms. The derivative term of equation (4) may then be expressed, in the
frequency domain, as follows:
Derivative action and time constant
jω T
D
F()jω = K (9)
p
1+ jω T
or
proportional action, derivative action and time constant
1+ jω T
D
F()jω = K (10)
p
1+ jω T
where
T is the time constant of a first order time delay.
T
D
The ratio may be constant for all adjustable values of T (depending upon the design
D
T
T
D
of the controller). The ratio is then called maximum derivative gain or V .
D
T
4.3 Dial graduation of controllers
The action factors and action times as used in the equations shown above give an idealized
description of the performance of a controller. Their values may differ from the values which
are the graduations marked on the dials of the controller. The relationship between the dial
graduations and the effective values, i.e. the “interaction formula”, shall be provided by the

60546-1 © IEC:2010 – 13 –
manufacturer. The relationship may be expressed in algebraic form or by graphs, tables,
diagrams, etc.
5 General test conditions
5.1 Environmental conditions
As per IEC 61298-1:
5.1.1 Recommended range of ambient conditions for test measurements
Temperature range 15 °C to 35 °C
Relative humidity 45 % to 75 %
Atmospheric pressure 86 kPa to 106 kPa
Electromagnetic field value to be stated, if relevant
The maximum rate of ambient temperature change permissible during any test shall be 1 °C in
10 min. These conditions may be equivalent to normal operating conditions.
5.1.2 Standard reference atmosphere
Temperature 20 °C
Relative humidity 65 %
Atmospheric pressure 101,3 kPa
This standard reference atmosphere is the atmosphere to which values measured under any
other atmospheric conditions are corrected by calculation. It is recognized, however, that in
many cases a correction factor for humidity is not possible. In such cases, the standard
reference atmosphere takes account of temperature and pressure only.
This atmosphere is equivalent to the normal reference operating conditions usually identified
by the manufacturer.
5.1.3 Standard atmosphere for referee measurements
When correction factors to adjust atmospheric-condition-sensitive parameters to their
standard reference atmosphere value are unknown, and measurements under the
recommended range of ambient atmospheric conditions are unsatisfactory, repeated
measurements under closely controlled atmospheric conditions may be conducted.
For the purpose of this standard, the following atmospheric conditions are given for referee
measurements.
Nominal value Tolerance
Temperature 20 °C ±2 °C
Relative humidity 65 % ±5 %
Atmospheric pressure 86 kPa to 106 kPa –
For tropical, sub-tropical or other special requirements, alternate referee atmospheres may be
used.
– 14 – 60546-1 © IEC:2010
5.2 Supply conditions
5.2.1 Reference values
The values shall be specified by the manufacturer or agreed upon between user and
manufacturer.
5.2.2 Tolerances
As per IEC 61298-1:
1) Electrical supply
– rated voltage ±1 %
– rated frequency ±1 %
– harmonic distortion (a.c. supply) less than 5 %
– ripple content (d.c. supply) less than 0,1 %
2) Pneumatic supply
– rated pressure ±1 %
– supply air temperature ambient temperature ± 2 °C
– supply air humidity dew point at least 10 °C below controller
temperature
– oil and dust content
–6
• oil less than 1 × 10 by weight
• dust absence of particles greater than 3 μm diameter
5.3 Load impedance
As per IEC 61298-1:
The value given by the manufacturer shall be used as the reference value.
For electric controllers, if the manufacturer gives more than one value, the load impedance
shall be taken as equal to:
– the minimum value specified by the manufacturer for controllers with direct voltage output
signal;
– the maximum permissible value for controllers with direct current output signal.
Unless otherwise stated by the manufacturer, for pneumatic controllers, an 8 m length of
4 mm internal diameter rigid pipe followed by 20 cm capacity shall be used for load
impedance.
NOTE This arrangement is specified for steady-state tests on pneumatic controllers. For dynamic tests, a 100 cm
capacity may be used in place of the 20 cm .
5.4 Other test conditions
Other conditions to consider when performing general tests are as follows:
– on the input signals: spurious induced voltages or pressure fluctuations which may affect
the measurement shall not be present;
– controller position during operation: normal mounting position specified by the
manufacturer. Throughout each test, however, the mounting position of the controller
should not change by more than ±3° about any axis;
– external mechanical constraints: they shall be negligible.

60546-1 © IEC:2010 – 15 –
The limit of error of the measuring systems used for the tests shall be stated in the test report
and should be smaller than or equal to one-fourth of the stated limit of error of the instrument
tested.
5.5 Stabilizing the controller output
For the purpose of the following tests, the controller may be stabilized in the following manner
2)
(see Figure 2a ).
a) Set the controller in a closed loop configuration by putting the switch in position B. Set the
controller for reverse action, or the differential amplifier to a gain of –1.
b) Set the proportional band to 100 % if possible and unless specified otherwise.
c) Set the derivative action for minimum effect (minimum rate time or off).
d) Set the integral action for maximum effect (minimum reset time).
e) Set the set point to 50 %.
f) If necessary, adjust the bias of generator No. 3 in order to obtain the desired output.

Set point Set point
generator No. 1
Output
Controller
Load
under test
Measured value
Offset
Measured value/
measurement
output recorder
Damping
Measured value
± 1
generator No. 2
A B
A = open loop
Switch
B = closed loop
Bias
generator No. 3
IEC  1621/10
Generator No. 1   Generator for set point input
For controller with external set point
Generator No. 2   DC for steady state input
Step for integral action test
Ramp for derivative action test
Generator No. 3   Sine wave for frequency response test and accelerated life test
DC for fixed bias levels
2a) Arrangement for open loop or closed loop tests
—————————
)
Damping is sometimes necessary for stabilization.

– 16 – 60546-1 © IEC:2010
Flowmeter Atmosphere
w
Throttle valve
Controller
Circuit as in
under test
Figure 2a
x
Flowmeter Air supply
Measured value/ Throttle valve
output recorder
Damping
IEC  1918/10
2b) Arrangement for measuring air flow
Figure 2 – Test arrangements
6 Offset
6.1 Test set-up
The offset test only applies to controllers with integral action. The circuit arrangement shown
in Figure 2a or an equivalent arrangement shall be used.
The set point and the measured value shall be connected to the input of a differential
measuring device. The selector switch shall be set in position B, thus obtaining a stable
“closed loop” condition.
Changing the bias of generator No. 3 allows the controller output y to be varied over the full
span for any value of the controller set point value and measured value.
6.2 Initial conditions
Initial conditions shall be as specified in Clause 5.
6.3 Test procedure
6.3.1 Offset at different values of X
p
The offset will change for different values of proportional bands. The test procedures to
determine the offsets are as follows:
– If the controller being tested has scale markings not directly in terms of proportional band,
or reset and rate times, the relationship of such markings to the parameters used in this
standard needs to be established. The method specified in this clause shall be used with
the instrument set to the scale markings which correspond to the values specified.
– With the controller stabilized in accordance with 5.5, adjust the bias of generator No. 3
until the output is 50 %. After allowing sufficient time for the controller output to stabilize,
measure the offset.
– The measurement shall be repeated with the proportional band adjusted to the minimum
value and then to the maximum value (or to the nearest scale markings).

60546-1 © IEC:2010 – 17 –
– Set the proportional band to 100 %. Repeat measurements as described above for all nine
combinations of the three values of the set point: 10 %, 50 % and 90 % of span and the
three values of output: 10 %, 50 % and 90 % of span.
– Switch the controller to direct action. At the same time adjust the gain of the differential
amplifier to –1. Measure offset with X = 100 %, set point = 50 % and output = 50 %.
p
– Further measurements may be made with other values of the proportional band or of the
set point at special points, in order to interpolate between some preceding readings where
there are significant variations in the offset.
– Offset shall be reported expressed in per cent of span of measured value.
6.3.2 Effect of changes of reset and rate time
Adjust set point to 50 %, output to 50 % and proportional band X to 100 %.
p
With the reset time set to its minimum value, change the rate time from its minimum value to
an intermediate value and then to the maximum value (for example 6 s, 12 s and 120 s).
With the rate time set to its minimum value, change the reset time from its minimum value to
an intermediate value and then to the maximum value (for example 6 s, 12 s and 120 s).
The offset shall be measured for each condition.
7 Dial markings and scale values
7.1 Verification of set point scales
The majority of controllers with internal set point sources have accessible terminals where the
effective set point signal can be measured. When this is so, the following test shall be carried
out.
The set point indicator shall be set in turn to the 0 %, 20 %, 40 %, 50 %, 60 %, 80 % and
100 % markings of its scale, and the corresponding values of the generated set point signal
shall be measured. The procedure shall then be repeated for settings in descending order, i.e.
100 %, 80 %, etc., down to 0 %.
The above procedure shall be repeated at least three times.
Determine the difference between the indicator reading and the generated value at each
setting. Express the difference in per cent of the set point span. Report the following:
a) average upscale error;
b) average downscale;
c) average error;
d) hysteresis.
7.2 Proportional action
The circuit arrangement shown in Figure 2a, or an equivalent arrangement should be used.
7.2.1 Initial conditions
The reference conditions are as specified in Clause 5.
7.2.2 Test procedure
The test procedure is as follows:

– 18 – 60546-1 © IEC:2010
– Adjust the set point to 50 %. Set the proportional band at 100 % (or the nearest scale
marking).
– Stabilize the output at 50 %.
– Adjust integral action to minimum effect (maximum reset time or off).
– Adjust derivative action to minimum effect (minimum rate time or off).
– Open the loop connection (switch in position A), and set controller action to direct action
mode.
– Vary the measured value signal over the range necessary to change the output from
minimum to maximum and note the corresponding measured value and output signals.
Measurements shall start with a measured value signal of 50 % and subsequent signals of
30 %, 70 %, 10 %, 90 %, 0 %, 100 % in that order.
– This procedure shall be carried out without interruption and as rapidly as possible to
minimize the effects of residual integral action.
– These measurements shall be repeated with the proportional band set at the two extreme
scale markings. For measurements at proportional band settings smaller than 100 %,
measured value signals shall be used such that the corresponding output signals are 50 %,
30 %, 70 %, 10 %, 90 %, 0 % and 100 %.
– Measurement shall be repeated at 100 % proportional band setting, but with controller set
to reverse action.
– A graph of the output signal plotted against the measured value signal (as percentages)
shall be plotted as in Figure 3.
The average proportional action factor (K ) shall be determined for each proport
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