Subject: Re: Lehman seismograph > Hi PSN members. Thanks for welcoming me to the PSN network. I have recently decided to build the Lehman seismograph.. I have completed the Transducer part of my "Lehman" and I am about to build an amplifier (which I dread[can they be purchased or "requisitioned" anywhere])?. I have a small problem though and I hope that you may have some thoughts on it. The only> feasable place for me to place the seismograph seems to be in my basement > which has a thin carpet in it over a concrete floor. Do I need to cut the > carpet away(the size of the Lehman base)? What do you think of the idea of > using VERY LARGE and SHARP screws that would penetrate the carpet and they > can also be used for Leveling? I have heard of some people using their > seismographs on other than the ground floor (wouldn't the waves be baffled/diminished)? > Any thoughts would certainly be appreciated. Thank you very much, Ed. > > > > > > > > > ----- Original Message ----- > From: "Larry Cochrane"
> To: "Ed Ianni" > Sent: Monday, December 18, 2000 12:41 AM > Subject: Re: Lehman seismograph > > > > Ed, > > > > First go back to the knife edge. Since a Lehman is a horizontal sensor you > > only want horizontal movement of the boom. To get the boom to stabilize > you > > need to position the top pivot point (where the wire meets the holder) > > slightly before the bottom pivot point (the knife edge). As the angle > > becomes straight up and down the boom will become more unstable. This is > > also how you set the period. The period will increase as the angle becomes > > more straight up and down. You can adjust the angle by lifting up the back > > end of the sensor. This will change the top and bottom angle. First start > > with a large angle and no damping. The boom should come too rest in the > > center of the sensor. As you lower the backend of the sensor the > oscillation > > period should increase. At some point the boom will become unstable. At > that > > point increase the angle a little and check the period. It should be > between > > 10 and 20 seconds. > > > > Hope this helps and good luck. > > > > -Larry Cochrane > > Redwood City, PSN > > > > ----- Original Message ----- > > From: Ed Ianni > > To: cochrane@.............. > > Sent: Saturday, December 16, 2000 7:28 PM > > Subject: Lehman seismograph > > > > > > Dear Mr. Cochrane; > > I am building the Lehman home seismograph. I am unable to get the > > boom stabilized although everything is level. I have used a "knife point" > > and a "rounded end" but the centering of the boom remains difficult and > > inconsistent. Any suggestions would help. Thank You Very Much. Ed. > > > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>