Try using a bubble level to know when the boom is level. Then tilt the end =
of the boom down, never up. I normally start by using a level to make sure =
the vertical upright is at zero degrees and then I level the boom. I then a=
dd about 1-5 degree of tile in the  upper most point of the upright in the =
direction of the boom. I have three level screws the base plate and a machi=
ne screw in the end of the boom to make the adjustment.=20
Regards, Stve Hammond PSN San Jose Aptos, CA

-----Original Message-----
>From: J=C3=B3n Fr=C3=ADmann 
>Sent: May 9, 2009 4:28 PM
>To: psn-l@..............
>Subject: Re: Incresing the period of a lehmans seismomter ?
>
>Hi all
>
>Thanks for the help of the weeks. I could not have fixed the issues with
>out you all.
>
>I am still having minor issues adjusting the period of my lehman sensor.
>I am not sure if I have to move the boom up or down to increase the
>period of my sensor.
>
>Regards.
>J=C3=B3n Fr=C3=ADmann.
>
>On f=C3=B6s, 2009-05-08 at 05:41 +0000, JAMES RIDOUT wrote:
>> Jon,
>>       I found it very confusing when setting the period for my
>> seismograph, and for a=20
>> long time took the period to be the time it takes the arm to swing
>> from one side to the
>> other.( I could never get much more than 10 seconds)!!.
>>  But apparently I am wrong, The period is the time it takes for the
>> arm to swing
>> past the same point in the same direction twice. So if you hold the
>> arm towards you
>>  and let it go, as it passes the centre, start a stopwatch, then
>> let the arm go to the other side,
>> then back towards you , and as it passes the centre again press stop.
>> This is the period.
>>   Anyone please correct me if I am wrong. !!.
>>                                                                 James
>>=20
>> --- On Fri, 8/5/09, J=C3=B3n Fr=C3=ADmann  wrote:
>>=20
>>         From: J=C3=B3n Fr=C3=ADmann 
>>         Subject: Re: Incresing the period of a lehmans seismomter ?
>>         To: psn-l@..............
>>         Date: Friday, 8 May, 2009, 2:08 AM
>>        =20
>>         Hi all
>>        =20
>>         I got the period down to 6 seconds at the lower end, but at 4 se=
conds
>>         the high end. But I have to do it adjust the period really slowl=
y. I am
>>         not sure what I can detect at 6 seconds.
>>        =20
>>         Geoffrey, I know what you mean. I am trying to understand someth=
ing in a
>>         diffrent language and am trying to understand something that I h=
ave not
>>         got a big traning on.
>>        =20
>>         Regards.
>>         J=C3=B3n Fr=C3=ADmann.
>>        =20
>>         On fim, 2009-05-07 at 17:04 -0700, Geoffrey wrote:
>>         > Gee, I believe this to be one of those
>>         > garden gate seismometers.
>>         > I always thought of it as a modified
>>         > pendulum changing the acceleration of gravity
>>         > in a trigonometric fashion.
>>         > This means the mass is the lowest point on the lever arm
>>         > or you can not have stability.
>>         > It manipulates the pull of gravity
>>         > like Sine or Cosine of the angle relative
>>         > to horizontal.
>>         > I believe you guys are thinking much more
>>         > complex then myself.
>>         > You more than likely will never
>>         > take souls like me very serious.
>>         > Sort of like Rodney Dangerfield ???
>>         >=20
>>         > ----- Original Message -----=20
>>         > From: "J=C3=B3n Fr=C3=ADmann" 
>>         > To: "PSN-Postlist" 
>>         > Sent: Wednesday, May 06, 2009 7:54 PM
>>         > Subject: Incresing the period of a lehmans seismomter ?
>>         >=20
>>         >=20
>>         > Hi all
>>         >=20
>>         > Tomorrow I am going to make the final changes to my lehman sei=
smomter. I
>>         > hope that this changes make the seismomter get down to 20 seco=
nds period
>>         > at most.
>>         >=20
>>         > The only thing that I need to know is this. What is the best w=
ay to
>>         > increase the period of my lehman seismomter ? Moving the boom =
down or
>>         > up ? Or do I have to do something else.
>>         >=20
>>         > Regards.
>>        =20
>>         __________________________________________________________
>>        =20
>>         Public Seismic Network Mailing List (PSN-L)
>>        =20
>>         To leave this list email PSN-L-REQUEST@.............. with
>>         the body of the message (first line only): unsubscribe
>>         See http://www.seismicnet.com/maillist.html for more information=
.
>
>
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>
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