PSN-L Email List Message

From: Dick Webb dwebb002@.............
Date: Mon, 18 Aug 2008 10:11:06 -0400


I am rather late to this thread, but I am running 201 and happen to have 
a brief publication from Sprengnether on it's theory and how to adjust 
the unit.  They rooted in their archives and found the article for me 
about 10 years ago.

Email me separately and I can fax a copy to you if it helps.

Dick Webb

> Thanks Meredith.  I appreciate all the recommendations and tips for 
> adjusting what I think is a "beautiful piece of seismic equipment".  
> Your email has re-inspired me to really tackle this challenge.  I will 
> let you know how it turns out. 
> Many thanks again for you wisdom and help.
> James Allen
>     ----- Original Message -----
>     *From:* meredith lamb 
>     *To:* psn-l@.............. 
>     *Sent:* Friday, August 15, 2008 8:35 AM
>     On Thu, Aug 14, 2008 at 9:34 PM, JAMES ALLEN      > wrote:
>         Meredith Lamb or any member using a Sprengnether 201 Long
>         Period unit:  There is an scale on the front of mine with the
>         indicator pointer that is at the fourth line from the top,
>         which is essentially at the top stop, and will normally
>         oscillate to the 6th line from the top.  Is this where it is
>         supposed to be or should it be centered on the 20 unit scale
>         which after a year of off and on fiddling seems impossible?
>         James Allen  
>             Hmmm....either its my computer malfunctioned or ?, but
>             here I see my response to Randall showing up below your
>             message above???
>     James,
>     It "sounds" like you need to give some more slack to the top
>     wire (top rear rotating knurled nut) ...just to allow the
>     frame/mass to come
>     further down, which then allows the vertical seismometer boom/mass
>     to get within the true center range of your
>     boom range/pointer mechanism.  It normally should be able to range
>     over the entire pointer scale of course.  My wild guess is that
>     the previous
>     owner/s had the same (which IS entirely solvable) problem also;
>     but didn't do the necessary adjustment/s.
>     Remove the coil and dampening coil wires before exploring the
>     adjustment mechanisms.  I don't know what you've done before; so, all
>     I can do is text the below.
>     At the rear top is a knurled round threaded wire adjustment
>     which will raise/lower the wire (and which changes the period). 
>     Try rotating that
>     slowly over whatever reaction range conjunction with
>     varying the front set screw, which you'll need to do probably
>     constantly.  Its
>     entirely possible that even a slight partial rotation or more;
>     will get you into a full range of its indicator pointer. 
>     Another potential "indicator/answer" could lie in your front
>     single set screw adjustment setting.  Try rotating that over a
>     reasonable range
>     and observe whether the boom/mass hits the stop at the top the
>     majority of the time.  If (the boom/pointer) hits the top stop
>     limit and stays there the
>     majority of the set screw range change; then that reaction would
>     might re-affirm you need for more wire slack as above.
>     Adjusting both the front set screw and the top back screw is
>     critical for this "boom/mass balance/pointer range" or in short;
>     just being able to
>     see its oscillation movement range.  The whole thing is kind of a
>     crude weight balance with the spring acting as kind of a varying
>     pivot force.
>'ve done all this before (?), and it still tends to go
>     to the upper range limit/stop....then you might actually have to
>     unclamp the
>     compression wire fitting and feed abit more wire down.  Thats a
>     really nasty job, as you'll be physically fighting the strong
>     spring tension
>     while trying to place the wire lower and also be ready to tighten
>     the compression wire clamp.  Its possible that the previous
>     owner/s might
>     have cut off the exposed wire coming out of the wire adjustment at
>     the top/back (?), there should normally be some wire coming out there?
>     If there isn't any wire....and you're at the limit of
> may have to rewire it to give more room/slack of
>     course.  We can get
>     into that if necessary.
>     I have a love-hate relationship with this coil/magnet vertical.  I
>     like its long mechanical period; but I hate its temperature
>     sensitivity.  All in all, its
>     worth fussing with....theres no real mechanical alternative of
>     course; outside of electronic extension of lesser period gizmo's.
>       Most
>     amateurs have no vertical whatsoever....
>     Take care, Meredith

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