Hello from San Diego:
Jon Griver disagrees that IEC 601 can be included in a generic
safety standard. He makes this statement because he believes
that SELV is not applicable to medical equipment.
Let's take a look at a block diagram for the various isolation
systems required for protection from electric shock:
+--------------+ +-------------------------+
...|Secondary HV |-----| HV interconnect |
. +------.-------+ +-------------------------+
. .
+-------+ . +--------------+ +-------------------------+
|Primary|--+--|Secondary SELV|.....|Non-isolated interconnect|
+-------+ | +--------------+ . +-------------------------+
| .
| +--------------+ . +-------------------------+
+--|Secondary ELV |.....| Isolated interconnect |
+--------------+ +-------------------------+
Most products include primary circuits. These circuits must be
isolated from all accessible conductive parts and from any
secondary circuits that might be accessible through interface
connectors, antenna connections, etc.
Most secondary HV circuits must be treated the same way as primary
circuits.
Most secondary ELV circuits must be isolated in a manner similar
to primary circuits and secondary HV circuits. They must be
isolated from all accessible conductive parts and from any secondary
circuits that might be accessible through interface connectors,
antenna connections, etc., by at least Basic Insulation.
Interconnect circuits can be any of three types, HV, non-isolated,
or isolated. All products can have any of the three types.
Patient connections are usually required to be isolated connections,
but can be non-isolated, in which case they must be current-limited
regardless of voltage.
My point is that many products use isolated interconnects. IEC 950
telephone interconnects are isolated. Some IEC 1010 measuring
circuits are isolated. Most IEC 601 patient circuits are isolated.
SELV is used in medical products, but cannot be used for patient
connections unless it is also current-limited.
I still contend that we could use ONE standard for all these products.
The only difference will be in the values of dielectric withstand,
leakage current, etc.
Regards,
Rich
+===========================================================+
|Richard Nute |Quality Department |
|Hewlett-Packard Company |Product Regulations Group |
|San Diego Division (SDD) |Tel : 619 655 3329 |
|16399 West Bernardo Drive |FAX : 619 655 4979 |
|San Diego, California 92127 |e-mail: ri...@sdd.hp.com |
+===========================================================+
