Let us say we are looking for EQ at M5 or above from anywhere in the world
and not the 4.5 of a Richter device.
How much mechanical advantage must we have to detect this
motion using a simple lever arm and lets say bouncing a laser light 
between two
surface silvered mirrors ?
I think you might get a mile of mechanical advantage this way.
Talking about increase of motion and not the force of a lever.
The ratio between the two ends of the fulcrum is of
what I speak for mechanical advantage of motion.
All the amplification happens, with this ratio.
Two opposed mirrors are a decent way to keep things relatively small.
Like sitting at the Barber shop looking at your reflection
fading into the distance many times over.
I just did this very same thing with my web camera
pointing into the monitor.



On 3/27/2013 12:28 PM, Brett Nordgren wrote:
> The only problem I can see is that the sensitivity you typically find 
> in a good instrument may be somewhat higher than what you are 
> considering.  For example, with the FBV instruments being operated by 
> Dave Nelson, a 2 Hz sinusoidal ground motion which registers 10 counts 
> peak-peak on Larry's A/D would represent a ground motion of ~8nm p-p 
> or about 18x the 0.44nm diameter of a large atom (Potassium).  So one 
> A/D count at 2Hz represents a motion of about 1.8x an atomic 
> diameter.  And most seismic observatories using 24-bit A/Ds are about 
> 5x more sensitive.
>
> For a really good instrument, one needs to be thinking in terms of 
> devices which can detect very small motions, though, in practice, an 
> instrument's true sensitivity will be determined by its internal 
> noise, not simply its bit-resolution.
>
> Regards,
> Brett
>
> At 06:47 PM 3/26/2013, you wrote:
>> On 26/03/13 23:56, Geoff wrote:
>>> I like the idea of using a WEBcam or something to look at the red dot
>>> then use a custom program to read the video and turn the graphic data
>>> into rectangular coordinates of a standard four quadrant graph
>>> with the point resting in the center of the graph
>>> But to do this in near real time may not be possible for myself to do.
>>> The max rate will be like 30Hz to 60Hz which is a video frame rate.
>>> Video is usually encoded and needs to be uncompressed.
>>> Uncompressing video takes lots of time to do so like a
>>> series of BMP captures at whatever rate would be the thing to do.
>>> You would take screenies at like 30 per second in a modulo fashion
>>> then save all after an alarm and the series of like
>>> 108000 BMP images would be decoded into a series of (X,Y) 
>>> coordinates ??
>>
>> This sounds a bit like a modified optical mouse.
>>
>>
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