Brett,

Check - http://www.allaboutcircuits.com/vol_2/chpt_12/6.html - page 7, It 
relates to capacitive sensors, I tried
this circuit and it worked fine.

There is a book called "the Inventor of Stereo" by Robert C. Alexander, 
published by Focal Press. The book
gives an account of the short life (38 years) of Alan Blumlein and most of 
his 128 patents.

Ted




----- Original Message ----- 
From: "Brett Nordgren" 
To: 
Sent: Tuesday, December 04, 2007 2:51 AM
Subject: Re: HS-10 manual


> Andreas,
>
> Sorry to hear about your HS-10 problem.
>
> However, I was also interested in your VBB project.  Had you ever 
> considered using a feedback system to stabilize the mass position?  It's 
> not a trivial undertaking, but once working, it might help a lot.
>
> Where can I see a description of the Blumelein Bridge?  Capacitive sensors 
> have always seemed like a good approach to me, and I'm interested in 
> learning about as many designs as I can.
>
> Good luck with your project.
>
> Brett
>
> At 11:05 PM 12/2/2007 +0100, you wrote:
>>Jack,
>>
>>thank you very much for doing this test! Your findings confirm my decision
>>to (try) to return
>>it to the dealer. He is on holidays now, so communication is somewhat 
>>slow.
>>He has a second HS-10, maybe he will test this one with the simpler 100 k
>>resistor test for
>>linearity. But I expect a similar result..
>>Maybe I should reactivate my VBB project instead. I tried to reproduce a
>>very compact
>>VBB design (inv. pendulum) from a scientific journal with a small mass
>>(~50g) and blumelein bridge  capacitive
>>displacement sensor. It worked quite well for the small size. I could see
>>the 6s microseisms clearly and
>>a ~6 quake in Papua NG. But I had some mass drift problems and lost my
>>interest in it.
>>
>>Andreas
>               My e-mail address above should be working, but if not
> you can always use my mail form at: http://bnordgren.org/contactB.html
>                            using your Web browser.
>
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