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Micromanipulators and Isolation tables!

r norman rsn_ at _comcast.net
Tue Nov 4 20:06:33 EST 2003

On Tue, 04 Nov 2003 23:57:43 GMT, Giddeon Nyquist
<giddeon_nyquist at hotmail.com> wrote:

>Thanks for the input Francis, but I'm still in trouble here.  I think I 
>may have fixed it today but I feel its only a temporary fix.
>> Does jumping up and down on the floor make the shakes worse?
>> (Get someone to do this for you while you watch.)
>Yes it does.  But you would think that if the table is properly isolated 
>this wouldn't happen.  This is one of my problems.
>> I've only ever used Narashige or modified Huxley manipulators -
>> no shakes with them.
>The Narishige manipulators rule, but I only use them for sharp electrode.  
>I really can't patch anything with Narishige. 
>> Do the shakes happen all the time, or just when you are moving
>> the electrode? Does the micromanipulator have servo motors? If
>> so, what happens when they are powered off?
>The manipulator does indeed have motors. When its powered off it the 
>shakes are still there.
>> Do you have an A/C unit blowing air round the room?
>That is funny that you should mention that, since we do have a lot of 
>vents in the lab.  But I don't think that is the MAIN problem since when 
>I surround the recording chamber and the electrode with cardboard to 
>block air currents the electrode still shakes.
Vibration isolators only dampen vibration above a certain cutoff
frequency.  Then do not "eliminate" it. Low frequency vibrations, in
particular, are hard to eliminate.

Look at the suface of the water in a wide flat dish, like a petri
dish.  Do you see vibrations or ripples?  Put the dish on the floor.
Are they much worse?  (You might be talking about vibrations too small
to see in the water.  Then again, you might be talking about
vibrations magnified in the electrode mounting arm).

In any event, if the floor really is rumbling that bad you are in some
trouble.  Where are the elevator motors for your building?  the
building ventilation fan motors?  the hood fan motors?  Do trucks
rumbling down the street change things?  Depending on the building
design, all these can be major factors.  Or they can be absolutely

It's a toss-up which is worse, finding and eliminating vibration or
finding and eliminating ground loops and line voltage electrical

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