Subject:
Re: Plastic Wrapper
From:
Kevan Hashemi <hashemi@opensourceinstruments.com>
Date:
Fri, 15 Dec 2006 10:00:02 -0500
To:
Helene Mainaud Durand <Helene.Mainaud.Durand@cern.ch>

Dear Helene,

Thanks for the photograph of three wrapped wires. I can't see any measurement scale in the picture, but there are pencil lines. My pencil lines are about 700 um thick. Comparing to the pencil lines, I estimate these wires to be around 500 um thick. The wrapper is much thinner than I thought: less than 100 um. There are two wrappers wound in opposite directions. These will have opposite effects upon the measurement. Also, the wrapper occupies less than 20% of the wire surface.

So, let me repeat my calculation. With a dielectric constant of 3, and <100 um thickness, the wrapper changes the apparant position of the wire by <70 um. It covers <20% of the wire, so the effect upon your measurement will be <15 um. There are two wrappers in opposite directions, which should lead to an 80% cancellation of each effect, which leads <3 um.

In short: I believe you.

The same argument will apply to our optical measurement. The opposing wrappers will cancel one another.

In short: we can use the same wires.

So, I'll proceed with making our prototype.

Yours, Kevan

Helene Mainaud Durand wrote:

> Dear Kevan,
>
> Please find here enclosed a macro photo of the wire and its wrapper.
> According to the manufacturer of the sensors, this wrapper is nearly
> invisible for the measurement. We have carried out some tests at
> CERN, and there was no effect of this wrapper on the measurement when
> we were moving the sensor w.r.t. the wire. Concerning the optical
> WPS, we have other wires with no wrapper, that can be used (the
> conductivity of the wire is not important in that case).
>
> Best regards,
>
> Hˆ©lˆ®ne.


-- 
Kevan Hashemi, President
Open Source Instruments Inc.
www.opensourceinstruments.com