PSN-L Email List Message

Subject: Re: My first Sensor
From: "tchannel" tchannel@..............
Date: Wed, 20 Sep 2006 22:31:06 -0600

Hi John, Thanks for the reply.
Presently it is not dampen at all.   I know the importance of this and will 
get that going directly, but when I blow on the beam it seems to return to 
full stop in maybe 10 to 15 seconds by the clock, producing a nice image, 
that does not go on for ever.  I was hoping to prove the amp and filter were 
working then address the damp.  I also am not 100% sure of my natural 
frequency of the horz pendulum, I will re adjust it to as close to 5,10 to 
20 seconds perhaps tomorrow.  When I first set it up I did not know how to 
figure it, but I now think I understand the math.  I have all the 
dimensions, I just need to move it to the bench for a redo.

As to the amp gain,  I think it is 100 not sure,  The set up I have, right 
or wrong, puts out a 1.5V for a low to a 7.5 volts for a high, a pot to 
adjust,  I set it at 2.0v.   I am using the DATAQ which is happy with, 0 to 
10 Volts  Again the filter is a Low pass set at 2.5Hz.   Before using the 
same amp with no filter, I would pick up cars on the street and stomps on 
the floor.  Now nothing unless I  blow on the beam or touching the sensor. 
Doing that I get nice signal.  Maybe with the addition of the filter I need 
to increase the voltage to the AD converter, from 2v to 5v?????

Any advise on any issues, or things to be aware of would be of great value,,
Thanks, Ted

----- Original Message ----- 
From: "John Popelish" 
Sent: Wednesday, September 20, 2006 8:41 PM
Subject: Re: My first Sensor

> tchannel wrote:
>>  1 I could use some advise, if the amp and filter seem to be okay or if I 
>> have over done something.
> Two open questions are the damping factor for the pendulum (how many 
> cycles do you see after you blow on it, before it settles?) and does your 
> amplifier provide enough gain?
>> 2  Another issue is, I am overwhelmed with confusion about "Seconds vs 
>> Hz"
> > I understand how to work with them and what they mean.
> > But the more I read the more confused I get.
> > The events come in low frequencies,
> > 10 to 20seconds  is that  0.1Hz. and .05Hz?
> Hertz means cycles per second.  Seconds can refer to the period of one 
> cycle (as you use it, above), but it can also refer to time constant of a 
> filter.  Then it refers to seconds per radian.  There are 2*pi radians in 
> a cycle.
>> Does that make everything above those Hz, or should I say, below those 
>> periods unwanted?
> > You can see I need help.
>> 3  Using AmaSies, what values do I set the Low pass filter,
> > and what values do I set the high pass filter,
> > for enhancing an enlarged detail trace?
> > Do I use both a low and high together.........
> > Some examples would be helpful.
> >
>> The little I have use them has just been trial and error, to get the best 
>> picture.
> Someone with more experience in seismology will have to help with these.
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