PSNet
The announcement of the availability of the update to IEC 60990,
shown below, has been circulating for a short time now. As Convenor
(Chairman) of this committee I had not generally circulated it to the PSNet
since it is not a product standard but a basic standard to be used by
product standards writing committees. As is usually the case, the
information in basic standards is excerpted or summarized in product
standards. Two IEC committees have been integrating this information into
their product standards for some time; IEC TC66/IEC 61010 (and the 1010
derivitive EN, CSA and UL standards) and IEC TC74/IEC 60950 (and the 950
derivitive EN, CSA and UL standards). The implementation of these
requirements into these two standards families is done in a slightly
different way and neither is a full copy of the IEC 60990 set of
recommended requirements. The certification requirements for the products
are contained in the end product standard. We expect to see ongoing
changes to the measurement of touch current at the product level to
accommodate the introduction of new technology which changes touch current
and exposes the user to this aspect of electric shock in some new way. If
you are a designer of test equipment making this measurement or want to see
the latest information regarding the measurement of touch current you
should buy a copy of this standard.
This new standard is now available from the IEC - either thru their
website or paper copy.
INFORMATION TECHNOLOGY / ELECTRICAL AND MAGNETIC MEASUREMENTS
"IEC 60990 (1999-08) - Methods of measurement of touch current and
protective conductor current"
Defines measurement methods for d.c. or a.c. of sinusoidal or
non-sinusoidal waveform, which could flow through the human body,
andcurrent flowing through a protective conductor. The measuring methods
recommended for TOUCH CURRENT are based upon the possible effects of
current flowing through a human body. In this standard, measurements of
current through networks representing the impedance of the human body are
referred to as measurements of TOUCH CURRENT. These networks are not
necessarily valid for the bodies of animals. The basic safety publication
is primarily intended for use by technical committees in the
preparation of standards in accordance with the principles laid down in IEC
Guide 104 and ISO/IEC Guide 51. It is not intended for use by manufacturers
or certification bodies. It has the status of a basic safety publication in
accordance with IEC Guide 104.
Milton Cox, Secretary of IEC Technical Committee 74 (Safety and energy
efficiency of IT equipment), provides the following information on this new
publication: "The second edition of IEC 60990 has been issued as an
International Standard replacing the first edition issued as a technical
report in 1990. Input from users of the technical report has resulted in
the following principle changes included in the second edition:
- provision of an earthing alternative for testing to accommodate some test
situations.
- provision of a more detailed description of the design and calibration of
the measurement network - as a result the component tolerances have been
deleted from the network diagrams.
With the publication of the second edition, it is expected the use of the
precise terms 'touch current' and 'protective conductor current' and the
measurement techniques will be used more extensively by technical
committees."
ICS Codes: 17.220, 35.020 - TC 74 - 109 pp. - CHF 153.00
- - - - -
Peter E Perkins
Principal Product Safety Consultant
Tigard, ORe 97281-3427
+1/503/452-1201 phone/fax
p.perk...@ieee.org email
visit our website:
http://ourworld.compuserve.com/homepages/peperkins
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