Hi Rolf I kinda like this one. It allows the light source and sensor to be located away from the machine workings. It also makes for easy experimentation on a live systemwithout affecting production. Thanks Regards John ----- Original Message ----- From: "Rolf" To: "Microcontroller discussion list - Public." Sent: Tuesday, September 26, 2006 12:45 PM Subject: Re: [EE]: High Speed Thickness Measurement > Since I have absolutely no idea about this sort of industrial control, > let me throw in my one idea... > > ... how about oblique laser light, and measuring the change in reflected > distance... let me explain... > > Run the tissue over a a roller which is measured precisely. Put a sensor > which can detect the wavelength of the laser light immediately above the > paper with perhaps a light tube. > > Shine the laser at a very oblique angle on to the tissue, and measure > the angle you need to shine the laser on in order to get the beam under > the light tube... like this... actually, perhaps a better method will be > to shine the laser at a known but very oblique angle, and to then use a > "heliostat" mechanism to track where the dot is reflected... like the > attached image. The thickness of the tissue will be proportional to the > angle you have to adjust the sensor to to get the sensor pointed at the > laser dot. > > Rolf > > John wrote: > > Thanks for the ideas guys. > > > > I will investigate the use of ultrasonic, because the final stage had a > > number of rollers on which this could work. > > > > I am also interested in the 10GHz meter because it provides other > > interesting measurements. > > > > Will keep you all posted on progress as it forges on. > > > > Regards > > > > John > > ----- Original Message ----- > > From: "Alan B. Pearce" > > To: "Microcontroller discussion list - Public." > > Sent: Tuesday, September 26, 2006 8:01 AM > > Subject: Re: [EE]: High Speed Thickness Measurement > > > > > > > >>>> This a stupid (maybe) idea (long way out of my field) > >>>> > >>>> > >>> No Idea is stupid Steve, thanks for the suggestion > >>> > >> So here is my suggestion. Assuming the paper can be run over a rounded > >> surface (it could be an existing guide roller) so that you know it is flat > >> against the surface (i.e. under some tension), then my thought was to use > >> ultrasonic sensors to measure the thickness difference between the paper > >> height and the roller. You could have a number of sensors across the width > >> of the paper if necessary. > >> > >> > >>>> Light permeability > >>>> For a lamp of given intensity the translucence of the sheet > >>>> could be used as a thickness measurement > >>>> This could work if the light source is self calibrating, > >>>> allowing for the gradual degradation of the lamp. > >>>> > >>> Anyone know how well this could be used to measure a change > >>> of fractions of a micron? > >>> > >> Yes. The way I would do it, taking the roller arrangement I suggested > >> > > above, > > > >> is to shine the light so it is shining along the tangent of roller onto a > >> linear CCD. The roller will cause a shadow, which you use as reference, > >> > > and > > > >> the paper will increase the shadow height. Readout speed will probably be > >> limited to the clockout rate of the CCD. > >> > >> -- > >> http://www.piclist.com PIC/SX FAQ & list archive > >> View/change your membership options at > >> http://mailman.mit.edu/mailman/listinfo/piclist > >> > >> > > > > > > ---------------------------------------------------------------------------- ---- ---------------------------------------------------------------------------- ---- > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist