PSN-L Email List Message

Subject: Re: Mini Lehman Damping
From: John Lahr johnjan@........
Date: Wed, 11 Jun 2008 18:53:38 -0700

Hi James,

Keep in mind that the damping/overshoot measurement is made directly on the
mass, not by reading the pen motion.  The pen motion is based on the 
velocity of
the coil within a magnetic field and is further modified by your 
amplifier filters.


At 11:24 AM 6/11/2008, you wrote:
>In a message dated 2008/06/11, jamesridout@.............. writes:
>>And as far as I can see The ideal amount is 0.7 - 0.8 and that 
>>means that if I walk up to the seismograph and the pen deflects 
>>10mm, then the pen should return 0.5mm in the opposite direction 
>>then back to zero. Is it me, or does this seem like too much.
>Hi James,
>        I draw a thin black line on a sticky label and mount it 
> vertical on the end of the mass.
>        Over the top of this, separated by maybe 1/16", I mount a 
> clear plastic ruler.
>        I use a x2.5 mounted magnifying glass to view the ruler and 
> the vertical line.
>        I move the ruler so that the line is on a cm ruler mark.
>        I use a rod or ruler as a lever resting on the baseplate to 
> slowly move the mass 10 mm to one side.
>        I remove the lever and watch what happens to the mass line.
>        It should go past the rest postion by ~0.5 mm and then 
> return to the rest postion.
>        The magnifying glass makes this fairly easy to observe.
>        Regards,
>        Chris Chapman


Public Seismic Network Mailing List (PSN-L)

[ Top ] [ Back ] [ Home Page ]