IEC TS 61902:1998
(Main)Household microwave ovens - Visual clarity of see-through oven doors
Household microwave ovens - Visual clarity of see-through oven doors
The technical report specifies the characteristics of the visual clarity of see-through microwave oven doors. The tests may also be applicable to cooking ranges and other appliances where the workload is enclosed but visible.
General Information
Standards Content (Sample)
TECHNICAL
IEC
REPORT
First edition
1998-09
Household microwave ovens –
Visual clarity of see-through oven doors
Fours domestiques à micro-ondes –
Transparence optique des portes de fours à fenêtre
Reference number
IEC 61902:1998(E)
Numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series.
Consolidated publications
Consolidated versions of some IEC publications including amendments are
available. For example, edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the
base publication, the base publication incorporating amendment 1 and the base
publication incorporating amendments 1 and 2.
Validity of this publication
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology.
Information relating to the date of the reconfirmation of the publication is available
in the IEC catalogue.
Information on the subjects under consideration and work in progress undertaken by
the technical committee which has prepared this publication, as well as the list of
publications issued, is to be found at the following IEC sources:
• IEC web site*
• Catalogue of IEC publications
Published yearly with regular updates
(On-line catalogue)*
• IEC Bulletin
Available both at the IEC web site* and as a printed periodical
Terminology, graphical and letter symbols
For general terminology, readers are referred to IEC 60050: International
Electrotechnical Vocabulary (IEV).
For graphical symbols, and letter symbols and signs approved by the IEC for
general use, readers are referred to publications IEC 60027: Letter symbols to be
used in electrical technology, IEC 60417: Graphical symbols for use on equipment.
Index, survey and compilation of the single sheets and IEC 60617: Graphical symbols
for diagrams.
* See web site address on title page.
TECHNICAL
IEC
REPORT – TYPE 2
First edition
1998-09
Household microwave ovens –
Visual clarity of see-through oven doors
Fours domestiques à micro-ondes –
Transparence optique des portes de fours à fenêtre
IEC 1998 Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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For price, see current catalogue
– 2 – 61902 © IEC:1998(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
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HOUSEHOLD MICROWAVE OVENS –
VISUAL CLARITY OF SEE-THROUGH OVEN DOORS
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising all national
electrotechnical committees (IEC National Committees). The object of the 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,
the IEC publishes International Standards. Their preparation is entrusted to technical committees; any IEC National
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the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between
the two organizations.
2) The formal decisions or agreements of the 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
National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form of
standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International Standards
transparently to the maximum extent possible in their national and regional standards. Any divergence between the IEC
Standard and the corresponding national or regional standard shall be clearly indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment
declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent
rights. The IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. In exceptional
circumstances, a technical committee may propose the publication of a technical report of one of the
following types:
• type 1, when the required support cannot be obtained for the publication of an International
Standard, despite repeated efforts;
• type 2, when the subject is still under technical development or where for any other reason there is
the future but no immediate possibility of an agreement on an International Standard;
• type 3, when a technical committee has collected data of a different kind from that which is
normally published as an International Standard, for example "state of the art".
Technical reports of types 1 and 2 are subject to review within three years of publication to decide
whether they can be transformed into International Standards. Technical reports of type 3 do not
necessarily have to be reviewed until the data they provide are considered to be no longer valid or
useful.
61902 © IEC:1998(E) – 3 –
IEC 61902, which is a technical report of type 2, has been prepared by subcommittee 59H: Microwave
ovens, of IEC technical committee 59: Performance of household electrical appliances.
The text of this technical report is based on the following documents:
Committee draft Report on voting
59H/75/CDV 59H/87/RVC
Full information on the voting for the approval of this technical report can be found in the report on
voting indicated in the above table.
This document is being issued in the type 2 technical report series of publications (according to
subclause G.3.2.2 of part 1 of the IEC/ISO Directives) as a $prospective standard for provisional
application# in the field of household electrical appliances, because there is an urgent need for
guidance on how standards in this field should be used to meet an identified need.
This document is not be regarded as an $International Standard#. It is proposed for provisional
application so that information and experience of its use in practice may be gathered. Comments on
the content of this document should be sent to the IEC Central Office.
A review of this type 2 technical report will be carried out not later than three years after its publication,
with the options of: extension for a further three years; conversion into an International Standard; or
withdrawal.
Annex A is for information only.
– 4 – 61902 © IEC:1998(E)
INTRODUCTION
After a general description of the concept of visual clarity and the reasons for considering it as a
performance factor, the ambient conditions are discussed. The proposed measurements and
evaluations are then described. Finally, some technical test results and comparisons with panel testing
results are given.
61902 © IEC:1998(E) – 5 –
HOUSEHOLD MICROWAVE OVENS –
VISUAL CLARITY OF SEE-THROUGH OVEN DOORS
1 Scope
This technical report specifies the characteristics of the visual clarity of see-through microwave oven
doors.
The tests outlined here may also be applicable to ranges and other household appliances where the
workload is enclosed but visible during the treatment.
2 Normative reference
The following normative document contains provisions which, through reference in this text, constitutes
provisions of this Technical Report. At the time of publication, the edition indicated was valid. All
normative documents are subject to revision, and parties to agreements based on this Technical
Report are encouraged to investigate the possibility of applying the most recent edition of the
normative document indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
IEC 60705:1988, Methods for measuring the performance of microwave ovens for household and
similar purposes
3 General
The visibility into microwave oven cavities may be a performance factor of interest to the user. Many
heating operations are of short duration and the user normally remains in the vicinity of the oven when
it is operating. Boiling and similar phenomena may begin and become vigorous within a very short
time. The appearance of browning in microwave combination ovens is another phenomenon which
may be important to follow.
The viewing screen of a microwave oven shall not allow microwave leakage and must therefore
provide an efficient path for the microwave wall currents in the cavity. The metal surface needed for
this is normally either a meshed metal grid or the remaining metal plate parts in a hole screen. For
protection and cleaning purposes, there are also glass plates or similar, both in front of and behind the
metal screen. All these components limit the visibility through the door by reduction of light
transmission and by patchiness due to the hole pattern, as well as reflection of external light by the
screen and its glass cover. There are also other contributing factors listed below but not included in the
technical measurements.
The term visual clarity expresses the contrast, resolution and colour saturation of the image of the food
load in a microwave oven cavity (or in a conventional oven) seen through the viewing screen. As
indicated by the word visual, the clarity is mainly a subjective expression. As a consequence, ranking
of ovens may be made by panel testing but some conditions are specified. The test room specifications
are given in 4.4. Other requirements for panel testing are given in clause 7.
A more technical series of tests using instruments and physical measurements is specified in clause 6.
Results are reproducible but the relevance of the test conditions and specifications � the
representativity of the test � may be limited because of differences in the common external conditions.
There are also some additional factors which influence the real and perceived visual clarity but are not
included in the technical tests since they are too complicated. However, such additional factors are
automatically included in a panel test. Their relative influence on the test results becomes subjective
and varies with ambient lighting conditions.
– 6 – 61902 © IEC:1998(E)
The additional factors are given below.
& Specularly reflected luminance caused by the outer glass or viewing screen. The disturbance to the
sight depends very much on the ambient lighting conditions. However, it becomes partially
quantified by the fact that the specified test room is diffusely illuminated.
& The reflectance of the cavity walls and the interior of the door. If the cavity back wall is white the
contrast deteriorates in comparison with a dull or stainless steel colour. A white inside of the door
improves the light intensity in the cavity when the door is closed.
& The colour (whiteness) of the external door area surrounding the viewing screen. A white area
around the outside of a darker viewing screen causes glare phenomena which disturb visual clarity.
& The thickness (hole length) of the screen holes in relation to the hole diameter. Long length holes
with a relatively small in diameter make the viewing sensitive to small oblique viewing angles.
& The size of the viewing screen in relation to the door opening. A small overall viewing screen will
reduce the viewing angles and limit the oven placement height.
Some test results and comparisons between technical and panel tests are given in annex A.
4 Test conditions, material and instrumentation
4.1 Light source in the cavity
The light source in the cavity is that provided with the oven. The oven is operated according to clause 8
of IEC 60705 with the cavity lamp(s) operating as in normal operation of the oven but the oven is not
operated with microwaves.
NOTE � It may be necessary to disable the microwave generator in order to obtain normal operation without microwaves.
4.2 Artificial cavity load for measurements
A 200 mm diameter and 20 mm high circularly cylindrical disc having a diffusely reflecting neutral grey
colour on its top and curved surfaces is used. The disc shall give (50 ± 10) % less reflected luminance
(cd/m ) than a white expanded polystyrene slab when illuminated from above with the luminances
measured at a 20° ± 3° elevation angle (the disc and slab are placed horizontally and their top surfaces
are illuminated vertically).
NOTE – In order to support the optical sensor during measurements, two small blocks with a half-square triangular cross-
section and having a small side length of about 30 mm and a height of 20 mm may be needed. The blocks must have the same
grey colour as the disc on all sides.
4.3 Instrumentation
A cosine-corrected and V(�) luminosity corrected light meter with external sensor is used for the
illuminance measurements. The height of the sensor body is to be less than 20 mm.
The instrument is also used with a built-in sensor to measure luminance. It is then placed on a tripod or
similar. This should not have any large dark areas and may be partially covered with white cloth or
similar, if needed.
4.4 Test room specifications
The light sources are two or three 36 W warm white, full colour, high-frequency driven (variable
intensity) fluorescent tubes with white light reflectors/diffusers.
NOTE 1 – The fluorescent light source is a compromise between incandescent and daylight source properties.
NOTE 2 – The diffusers are needed to adjust the balance between the vertical and horizontal illuminance specified below.
NOTE 3 – In order not to need excessive dimming of the fluorescent tubes, reflectors may not be needed and the diffusers may
be of the transmission rather than reflection type.
61902 © IEC:1998(E) – 7 –
The room is windowless and has no other light sources. The size of the room is to
...
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