ISO 12384:2010

INTERNATIONAL ISO
STANDARD 12384
First edition
2010-11-15
Aerospace — Requirements for digital
equipment for measurements of aircraft
electrical power characteristics
Constructions aérospatiales — Exigences relatives aux équipements
numériques de mesure des caractéristiques de puissance électrique
à bord des aéronefs
Reference number
©
ISO 2010
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©  ISO 2010
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ii © ISO 2010 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Symbols.1
5 Measurement requirements for the aircraft electric power characteristics.3
5.1 General rules, measurement states and the admissible errors of the measurement results .3
5.1.1 General .3
5.1.2 Measurement states.3
5.1.3 Admissible errors of the measurement results.3
5.2 Measurement of constant frequency (CF) a.c. power system characteristics.4
5.2.1 Steady state characteristics.4
5.2.2 Transient characteristics.8
5.3 Measurement of variable frequency (VF) a.c. power system characteristics .8
5.4 Measurement of d.c. power system characteristics (28 V or 42 V system).8
5.4.1 Steady state characteristics.8
5.4.2 Transient d.c. voltage.10
5.5 Measurement of current parameter.10
5.6 Measurement of power transfer characteristics .10
5.7 Measurement of voltage spike characteristics .10
5.8 Measurement of power factor .10
6 General requirements for the measuring equipment .11
6.1 Applicability .11
6.1.1 Efficiency.11
6.1.2 Operating environment.11
6.2 Performance and functions.11
6.2.1 Accuracy .11
6.2.2 Scope of the measuring equipment .11
6.2.3 Measurement resolution.11
6.2.4 Input impedance.11
6.2.5 Sampling frequency range .12
6.3 Electromagnetic compatibility .12
6.4 Human-machine interface project .12
6.5 The regulation of select measuring equipment .12
6.5.1 The measurement regulation of the data process software .12
6.5.2 Selecting requirement.12
Bibliography.13

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 12384 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 1, Aerospace electrical requirements.
ISO 12384 is closely allied with ISO 1540 and references from one to the other are freely used, particularly
from ISO 12384 to ISO 1540. The proper use of this International Standard through referencing the applicable
specific digital measurement methods should simplify the preparation of specifications and help to expedite
the purchase and acceptance of the digital measuring equipment.

iv © ISO 2010 – All rights reserved

Introduction
Various types of digital measuring equipment for electrical power characteristics are applied to the aircraft
electrical system. There is no International Standard for digital measuring equipment for electrical power
characteristics in the aerospace industry. The purpose of this International Standard is to explain, establish
and standardize specific methods for digital measurements of the aircraft electrical system. The intended use
of this International Standard is to define how to measure parameters of electrical characteristics in aircraft
electrical power systems. The specific measurement methods are included here, while the terminology and
general methods of digital measurement and signal processing are also presented. The requirements of digital
measuring equipment are verified by testing of the aircraft electrical system.

INTERNATIONAL STANDARD ISO 12384:2010(E)

Aerospace — Requirements for digital equipment
for measurements of aircraft electrical power characteristics
1 Scope
This International Standard specifies the requirements for digital measuring methods and digital measuring
equipment for aircraft electrical power characteristics, including accuracy, algorithms and digital measuring
equipment. The measuring equipment should be applied mainly for the use of laboratory or rig tests.
This International Standard can be applied to digital measuring equipment which is involved in the
measurement of power electrical characteristics of the power supply system, power distributing systems and
the utilization of equipment in aircrafts.
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.
ISO 1540, Aerospace — Characteristics of aircraft electrical systems
ISO 7137, Aircraft — Environmental conditions and test procedures for airborne equipment
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1540 and the following apply.
3.1
sampling frequency
reciprocal of sampling interval time
3.2
sampling time
total of sampling interval time
4 Symbols
Symbols used by this International Standard are listed in Table 1.
Table 1 — Symbols and definitions
Symbol Unit Definition
F power factor
P
F crest factor
C
f Hz steady state frequency
f Hz frequency modulation
m
I A steady state a.c. current
i A instantaneous value of a.c. current
j
j sampling serial, j = 1,2,3, . n
F % a.c. voltage distortion factor
d
n total number of sampling points during the steady state time
N cycle numbers during T
W
T sampling period
T s time of a period not to exceed one second
w
T s difference in time between the fundamental components of any two
θ
normalized phase voltages taken at consecutive zero crossings
traced in the negative to positive direction
t s difference in time between the fundamental components of any two
θ
phase voltages taken at consecutive zero crossings traced in the
negative to positive direction
U V steady state phase voltage
U , U , U V phase A, B and C steady state voltage
A B C
U V distortion of a.c. voltage
d
U V d.c. component of a.c. voltage
Adc
th
U V rms value corresponding to the j cycle
j
U V peak value of a.c. voltage for each cycle
P
U V voltage ripple
rm
U V voltage modulation
m
th
U n harmonic rms value of current or voltage
n
U V steady state d.c. voltage
dc
U V rms value of fundamental component of a.c. voltage
f
U V voltage imbalance
ε
U V rms value of a.c. distortion voltage
D
D % total harmonic distortion
TH
u V instantaneous value of a.c. voltage
j
u V instantaneous value of a.c. distortion voltage
Dj
u V maximum value of cyclic variation in relation to the mean level of
dmax
d.c. voltage during steady state operation
u V minimum value of cyclic variation in relation to the mean level of d.c.
dmin
voltage during steady state operation
u V instantaneous value of d.c. voltage
dcj
U V distortion of the d.c. voltage
Ddc
F % d.c. voltage distortion factor
ddc
Δt s sampling interval time
θ ° phase voltage displacement

2 © ISO 2010 – All rights reserved

5 Measurement requirements for the aircraft electric power characteristics
5.1 General rules, measurement states and the admissible errors of the measurement
results
5.1.1 General
The electric power characteristics measurement shall be implemented in accordance with the definitions of
ISO 1540 and the requirements of this International Standard.
5.1.2 Measurement states
5.1.2.1 Steady state
The measurement of steady state parameters shall be processed only when negligible changes in electrical
parameters appear. For example, no load state, rated load state, etc.
5.1.2.2 Transient state
The measurement of transient state parameters shall be processed in the transient state. Momentary
variations of a characteristic from its steady state limits, and back to its steady state limits may occur as a
result of a system disturbance. For example,
...