[ANSS-netops] l4c

Tue Mar 6 01:57:21 UTC 2012

Greg, Steve,

Interesting stories that I can't say I ever knew.  After talking to 
Scott Bowen at Sercel, he definitely verified that.  He's been with 
Mark Products/Sercel for 30 years and he remembers that the reversal 
was already in place when he started.  So, I'm guessing that IRIS and 
other university cooperators are using L-4C's that are reverse 
polarity from USGS networks?  Interesting.

The geophone cables/caps that we ordered, however, are all supposed 
to come out of the factory wired one way.  He acknowledged they made 
a mistake in manufacturing and missed it during QC.  Of course they 
are replacing the cables for us, but not after a bit of extra 
work.  Just wanted others to be conscience of the issue.

Dave

At 06:10 AM 3/5/2012, Greg Steiner wrote:
>FYI, the polarity difference is not restricted to just the L-4. All 
>sensors (nominally called geophones) manufactured by exploration 
>type sources are backwards versus seismological standards. This is 
>because the exploration standard is based on the movement of the 
>inertial mass not the case. for them movement of the inertial mass 
>up or in the desired direction produces a positive output. I'm a bit 
>surprised that the USGS was able to get them to invert their 
>connections in sensors made for them. this certainly muddies the water.
>Greg Steiner
>
>On 3/5/2012 6:00 AM, 
><mailto:anss-netops-request at geohazards.usgs.gov>anss-netops-request at geohazards.usgs.gov 
>wrote:
>>
>>Send ANSS-netops mailing list submissions to
>> 
>><mailto:anss-netops at geohazards.usgs.gov>anss-netops at geohazards.usgs.gov
>>
>>To subscribe or unsubscribe via the World Wide Web, visit
>> 
>><https://geohazards.usgs.gov/mailman/listinfo/anss-netops>https://geohazards.usgs.gov/mailman/listinfo/anss-netops
>>or, via email, send a message with subject or body 'help' to
>> 
>><mailto:anss-netops-request at geohazards.usgs.gov>anss-netops-request at geohazards.usgs.gov
>>
>>You can reach the person managing the list at
>> 
>><mailto:anss-netops-owner at geohazards.usgs.gov>anss-netops-owner at geohazards.usgs.gov
>>
>>When replying, please edit your Subject line so it is more specific
>>than "Re: Contents of ANSS-netops digest..."
>>
>>
>>Today's Topics:
>>
>>    1. L-4C sensors (Steve Estes)
>>
>>
>>----------------------------------------------------------------------
>>
>>Message: 1
>>Date: Sun, 4 Mar 2012 10:00:45 -0900
>>From: Steve Estes <mailto:estes at gi.alaska.edu><estes at gi.alaska.edu>
>>To: <mailto:anss-netops at geohazards.usgs.gov>anss-netops at geohazards.usgs.gov
>>Cc: Guy Tytgat <mailto:guy at passcal.nmt.edu><guy at passcal.nmt.edu>
>>Subject: [ANSS-netops] L-4C sensors
>>Message-ID: 
>><mailto:5F6AAFDB-1974-4021-BCAF-62796618FA90 at gi.alaska.edu><5F6AAFDB-1974-4021-BCAF-62796618FA90 at gi.alaska.edu>
>>Content-Type: text/plain; charset="us-ascii"
>>
>>We ordered some L4C's awhile back and discovered the same thing.
>>The polarity was reversed. Well, at least it was different.
>>After discussing the issue with the manufacture (I don't remember 
>>if it was Mark Products or Sercel),
>>we were told that they make all USGS orders oneway, and everyone 
>>else's the other way.
>>
>>As I recall the story, the USGS evaluated the original prototype 
>>and found the polarity reversed.
>>Mark Products, wanting to please their customer, manufactured all 
>>subsequent USGS L4C's to the USGS spec.
>>All others were made with the original polarity.
>>
>>Regards,
>>Steve Estes
>>
>>
>>>
>>>Date: Fri, 02 Mar 2012 13:34:11 -0800
>>>From: "David S. Croker" <mailto:croker at usgs.gov><croker at usgs.gov>
>>>To: <mailto:anss-netops at geohazards.usgs.gov>anss-netops at geohazards.usgs.gov
>>>Subject: [ANSS-netops] L-4C users beware
>>>Message-ID: 
>>><mailto:OFD86DC885.EBFA1C35-ON882579B5.00767C4A at usgs.gov><OFD86DC885.EBFA1C35-ON882579B5.00767C4A at usgs.gov>
>>>Content-Type: text/plain; charset="us-ascii"; format=flowed
>>>
>>>If you don't use Sercel L-4C sensors you can delete this.
>>>
>>>We recently found out the hard way that a batch of "new" seismometer
>>>caps were wired with reverse polarity from the factory.  This is
>>>something we have never really checked before.  The red lead
>>>(positive, high) should go to the bottom contacts (closest to the
>>>tip).  We haven't bought many replacements over the years but we did
>>>buy a batch of a dozen last year.  It appears they were all wired in
>>>reverse.  Fortunately we caught the problem before we had too many
>>>deployed and they were all a day trip away.
>>>
>>>If you have purchased new caps from Sercel in the past year I
>>>recommend you check the polarity.
>>>
>>>Dave
>>
>>-------------- next part --------------
>>An HTML attachment was scrubbed...
>>URL: 
>><http://geohazards.usgs.gov/pipermail/anss-netops/attachments/20120304/d40adf89/attachment-0001.html>
>>
>>------------------------------
>>
>>_______________________________________________
>>ANSS-netops mailing list
>><mailto:ANSS-netops at geohazards.usgs.gov>ANSS-netops at geohazards.usgs.gov
>>https://geohazards.usgs.gov/mailman/listinfo/anss-netops
>>
>>
>>End of ANSS-netops Digest, Vol 36, Issue 3
>>******************************************
>>
>_______________________________________________
>ANSS-netops mailing list
>ANSS-netops at geohazards.usgs.gov
>https://geohazards.usgs.gov/mailman/listinfo/anss-netops
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://geohazards.usgs.gov/pipermail/anss-netops/attachments/20120305/600e6461/attachment.html>