PSN-L Email List Message

Subject: Re: Channel, 1,2 and 3?
From: tchannel1@............
Date: Sun, 23 Mar 2008 08:08:34 -0600

Hi Folks,  I think I will do nothing at this time, and wait for an event 
from the E/W.  Once received I will post all three channel again.  Thanks 
for your answers, I found them all very helpful.    Ted

----- Original Message ----- 
From: "John Lahr" 
Sent: Sunday, March 23, 2008 5:29 AM
Subject: Re: Channel, 1,2 and 3?

> Hi Ted,
> My understanding of a long period physical pendulum is that sensitivity to 
> ground motion is sacrificed in order to obtain the long period.  Your Ch3 
> is probably working correctly, but is MUCH less sensitive to ground motion 
> than your Ch1 or Ch2.  That would be consistent with your observations.
> Cheers,
> John
> At 05:24 PM 3/22/2008, you wrote:
>>Hi Folks,  I just posted three data files, of the 6.2M ANDREANOF ISLANDS, 
>>ALEUTIAN IS. 080322.212412 as ch1, ch2 and ch3
>>Channel 1 is what I call a tiltmeter, just a normal pendulum with a 2 
>>second period.  It can only swing East and West.  It works well
>>Channel 2 is a vertical Spring Slinky II, also has a 2 second period.
>>Channel 3 is my newest on called a Nearly Balanced, a normal pendulum, 
>>with a 20 second period, It can only swing North and South.
>>Channel 1 and 2 recorded the event well.
>>Channel 3 did not record it at all.   I know it is working, as all three 
>>are recording the road construction, all three show the same large backhoe 
>>at the same moment in time.
>>Channel 3 is also sensitive to me moving around the upstairs.
>>I posted all three and filtered Channel 1 and 2, using Low pass 1, and 
>>High pass .05..   These filters did nothing on channel 3 so I posted it 
>>Perhaps someone can look at all three, to see if I have a problem.   I 
>>don't think it is over damped, if anything it is under.   Could this be 
>>the direction the channel is facing?
>>Thanks, Ted
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