EN 60068-2-40:1999

SLOVENSKI STANDARD
01-september-2001
Environmental testing - Part 2: Tests - Test Z/AM: Combined cold/low air pressure
tests
Environmental testing -- Part 2: Tests - Test Z/AM: Combined cold/low air pressure tests
Umweltprüfungen -- Teil 2: Prüfungen - Prüfung Z/AM: Kombinierte Prüfung -
Kälte/Niedriger Luftdruck
Essais d'environnement -- Partie 2: Essais - Essai Z/AM: Essais combinés froid/basse
pression atmosphérique
Ta slovenski standard je istoveten z: EN 60068-2-40:1999
ICS:
19.040 Preskušanje v zvezi z Environmental testing
okoljem
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME CEI
INTERNATIONALE
IEC
60068-2-40
INTERNATIONAL
Première édition
STANDARD
First edition
1976-01
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
Essais fondamentaux climatiques
et de robustesse mécanique –
Partie 2-40:
Essais – Essai Z/AM: Essais combinés
froid/basse pression atmosphérique

Basic environmental testing procedures
Part 2-40:
Tests – Test Z/AM: Combined cold/low
air pressure tests
CODE PRIX
J
Commission Electrotechnique Internationale
PRICE CODE
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur

CONTENTS
Page
FOREWORD 5
PREFACE 5
Clause
1. Introduction
1.1 General
1.2 Low air pressure
1.3 Temperature
1.4 Related documents
2. Object
3. General description
4. Description of test apparatus
4.1 Test chamber
4.2 Mounting 9
5. Severities
5.1 General
5.2 Preferred combinations of temperature, air pressure and duration 9
6. Preconditioning
7. Initial measurements
8. Conditioning
8.1 General
8.2 Procedure for heat-dissipating specimen without artificial cooling of the specimen and for non-
heat-dissipating specimen 11
8.3 Precautions when testing specimens with artificial cooling 13
9. Intermediate measurements
10. Recovery
11. Final measurements
Information to be given in the relevant specification 13
12.
FIGURES 15-17
– 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
–––––––––
BASIC ENVIRONMENTAL TESTING PROCEDURES –
Part 2: Tests – Test Z/AM: Combined cold/low air pressure tests
FOREWORD
1) The formal decisions or agreements of the IEC on technical matters, prepared by technical committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
2) They have the form of recommendations for international use and they are accepted by the National
Committees in that sense.
3) In order to promote this international unification, the IEC expresses the wish that all National Committees
having as yet no national rules, when preparing such rules, should use the IEC recommendations as the
fundamental basis for these rules in so far as national conditions will permit.
4) The desirability is recognized of extending international agreement on these matters through an endeavour to
harmonize national standardization rules with these recommendations in so far as national conditions will
permit. The National Committees pledge their influence towards that end.
PREFACE
This Recommendation has been prepared by subcommittee 50A: Shock and vibration tests, of
IEC technical committee 50: Environmental testing.
A first draft was discussed at the meeting held in Munich in 1973. As a result of this meeting,
a Secretariat draft was submitted to the National Committees under the Accelerated
Procedure and submitted for approval under the Six Months' Rule as Document 50B(Central
Office)184 in October 1974.
It has the status of a basic safety publication in accordance with IEC Guide 104.
The following countries voted explicitly in favour of publication:
Australia Poland
Austria Portugal
Belgium Romania
Canada South Africa (Republic of)
Czechoslovakia Spain
Denmark Sweden
France Switzerland
Germany Turkey
Hungary Union of Soviet
Japan Socialist Republics
Netherlands United Kingdom
Norway
BASIC ENVIRONMENTAL TESTING PROCEDURES
Part 2: Tests — Test Z/AM:
Combined cold/low air pressure tests
1.
Introduction
1.1 General
This publication deals with combined cold (with gradual change of temperature) and low air pressure tests for
both heat-dissipating and non-heat-dissipating specimens.
The object of the test is to determine the ability of components or equipment or other articles to be stored and
used under a simultaneous combination of low temperature and low air pressure.
This combined test should normally be used only if the effects of combined environments will not be revealed
by subjecting the specimen to single environments. The procedures given in this publication are limited to the case
of specimens which achieve temperature stability during the test procedure.
In the case of testing heat-dissipating specimens, this procedure applies only to the testing of one specimen at a
time.
1.2
Low air pressure
The test procedure applies to air pressure down to about 10 mbar. At air pressures below 10 mbar, phenomena
not taken into account in the design of this test procedure become important.
The relationship between altitude, pressure and temperature has not been indicated in this publication. Such
data should be obtained from special publications.
1.3 Temperature
1.3.1 The guidance given in the introduction to Publication 68-2-1, Tests A: Cold, for the application of tests
for non-heat-dissipating specimens versus tests for heat-dissipating specimens shall apply.
Note. — Non-heat-dissipating specimens are defined as in Clause 4 of Publication 68-1. The measurement of hottest spot temperature
must not be made at low pressure.
1.3.2 Heat-dissipating specimens should preferably be tested with no forced air circulation as for Tests A: Cold.
1.4 Related documents
Publication 68: — Basic Environmental Testing Procedure.
Publication 68-1: Part 1. General.
Publication 68-2-1: Part 2: Tests. Tests A: Cold.
Publication 68-2-13: Part 2: Tests. Test M: Low Air Pressure
Publication 68-3-1: Part 3: Background Information. Section One: Cold and Dry Heat Tests.
Publication 68-3-2 Part 3: Background Information. Section Two: Combined Temperature/Low Air Pressure
Tests.
— 9 —
2. Object
To provide a standard test procedure to determine the suitability of components, equipments or other articles
for use and/or storage under a combination of low temperature and low air pressure.
3. General description
This test is a combination of Test
Ab or Ad: Cold, and Test M: Low air pressure.
The specimen is first subjected to the appropriate severity of cold as indicated in the relevant specification. In the
case of operational tests, a check is then made to ensure that the specimen is capable of operation. With the tempera-
ture maintained at the indicated value, the chamber air pressure is then reduced to the appropriate severity as
specified in the relevant specification. These conditions are maintained for the specified duration. Test profiles
illustrating the procedure are shown in Figure la, page 15, and Figure lb, page 17.
4.
Description of test apparatus
4.1 Test chamber
The chamber shall be capable of maintaining the conditions specified for Test Ab (for non-heat-dissipating
specimen) or Test Ad (for heat-dissipating specimen) and for Test M. The requirement for the chamber wall tem-
perature does not apply during periods of temperature or pressure change.
Care shall be taken to avoid air contamination by ancillary equipment and devices and by the air introduced
when pressure is restored to normal.
4.2 Mounting
For the testing of a heat-dissipating specimen, the mounting of the test specimen shall comply with the require-
ments for Test Ad.
5. Severities
5.1 General
The severities, as indicated by temperature, air pressure and duration of exposure, s
...