[alma_na] FW: standards comments - Shillue

[Janet Bauer]

Bill was asked this morning to stand in for John Payne during today’s
1:00 pm ET teleconference.  Even though he didn’t have a lot of prep
time, he did write some comments and asked that I distribute them to the
other participants.

Janet

Janet Bauer
ALMA Project Secretary
NRAO - ALMA North American Project Office
2496 Old Ivy Road, Suite 226
Charlottesville, VA 22903
 
434.296.0296      (phone)
434.296.0255      (fax)
jbauer at nrao.edu (E-mail)


-----Original Message-----
From: Bill Shillue [mailto:bshillue at nrao.edu] 
Sent: Thursday, July 10, 2003 12:41 PM
To: jbauer at nrao.edu
Subject: standards comments - Shillue

Janet,

If you think it is appropriate you could forward these comments to 
particpants in the DH meeting today, though it is quite late and maybe 
will not be received in time. - Bill

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Comments on Standards in Doc Approval Queue

Bill Shillue 2003-07-10

I have read these standards and have insufficient expertise and time to 
comment in complete manner.
I was not aware of the comment deadline of July 15 until Tuesday, so I 
have not had time to put any comments on EDM. So I am including some 
comments here.

Given the scope and generality of these standards, it seems late in the 
project to be preparing and submitting them for approval. Some 
explanation should be forthcoming about how the preparation of these 
documents was unknown to most engineers.

As at least one of the standards claims, many of the suggestions are 
common sense. Some are obvious, some are subtle, and some are of 
questionable value. The questionable part comes in when the proposed 
savings, which comes mostly as an operational cost, is weighed against 
the increased construction costs.

Implementation of these standards will undoubtedly increase the cost to 
the project of the instrumentation that I am responsible for delivering.

How is the cost estimation to be handled?

On the other hand, in some cases this implementation may also improve 
the quality of the product. So I would suggest that we carefully 
consider which items require a *shall*, and also carefully consider what

the process for demonstrating compliance consists of.

After reading all of the reviewer comments, I think that the Electronic 
Design Document should be withdrawn or undergo major review. The number 
of objections and suggested additions and deletions is very large. Dave 
Browns idea of separating into documents for electrical, mechanical, and

electronic seems like a good idea to me.

Regarding the EMC document, it is not clear to me if this is meant to 
supercede, replace, or be used in conjunction wth the RFI document that 
C. Janes has prepared.

Electronic Design

EELE-00930-00/R,I : Cables shall be put in metal conduits or ducts. 
(This should only be for cables connecting major subassemblies or going 
more than some minimum distance)

3.3.3 EELEE-0014x0-00/R,I: The restriction to two or three types of 
optical connectors may be too restrictive. For example, for shielding 
requirements, the FC connector may not be the best solution. There are 
some new shielded fiber connectors coming ou tthat may be better. Also, 
the restriction to APC ferrules, instead of PC variety, may not be 
necessary for some subsystems, adding expense. Within a fully enclosed 
module there should be no restriction on type of connector. Adding 
something about the advisability of shuttered connectors for parts of 
the system where there is safety concern due to the level of light form 
the connector might be a good idea.

Another comment is that the Electronic standard does not include 
anything on optical or photonic components. For the master laser 
specification, we include, for instance :

xxx Reliability
Optical and photonic components used within the module shall satisfy 
Telcordia General Requirements [3] for reliability assurance wherever 
they are applicable, including but not limited to GR-468-CORE, GR?1209, 
GR?1221, GR?2883, and GR?2882.

EMC

Does the immunity to static discharge pose a difficulty for the diode 
multipliers, photomixers, and SIS devices on the Front Ends?

The hydrogen maser and master laser have magnetic field susceptibility 
that may or may not meet requirements.

Environmental

Earthquake specification is incomprehensible. Is this a survivability 
spec, or an operational one?

It is possible that the photonic reference system will not meet the 
earthquake and temperature shock requirements, operationally. Even a 
hint of an earthquake will likely cause the system to operate out of
spec.

I have some concern that shipping and handling of lasers might need 
special precautions.

Plugs and Connectors

No Comment