I believe that thickness measurement is done with a radioactive source 
and a "geiger" counter. The
thicker the material, the more attenuation. Easily calibrated.

--Bob

John wrote:
> Hi Vasile
>
> The temp and moisure content vary.
>
> Temp is dependant on the amount of steam being fed into the dryer drum, and
> the speed of the machine - both operator set. The moisture content varies
> depending on what the product requirement is - budget to luxuary and many
> stages inbetween.
>
> This doesnt mean that it cant be calibrated according to the conditions - it
> will just make it a very complex measurement.
>
> Regards
>
> John
> ----- Original Message ----- 
> From: "Vasile Surducan" <piclist9@gmail.com>
> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
> Sent: Monday, September 25, 2006 6:59 PM
> Subject: Re: [EE]: High Speed Thickness Measurement
>
>
>   
>> On 9/25/06, John <john@raystorm.co.uk> wrote:
>>     
>>> Hi Guys
>>>
>>> I would like some suggestions for a thickness measurement project that I
>>> have in mind. Its purpose when built will be to measure the thickness of
>>> tissue coming out of a paper machine - ave speed 1500m/min
>>>       
>> Microwave around 10Ghz, if the paper's temperature and moisture are
>>     
> constant.
>   
>> Vasile
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>
>   

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