This is a multi-part message in MIME format. --------------070904000707000304000604 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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 >> >> > > --------------070904000707000304000604 Content-Type: image/gif; name="Thickness Sensor.gif" Content-Transfer-Encoding: base64 Content-Disposition: inline; filename="Thickness Sensor.gif" R0lGODdhcAK3APcAAAAAAIAAAACAAICAAAAAgIAAgACAgMDAwMDcwKbK8EAgAGAgAIAgAKAg AMAgAOAgAABAACBAAEBAAGBAAIBAAKBAAMBAAOBAAABgACBgAEBgAGBgAIBgAKBgAMBgAOBg AACAACCAAECAAGCAAICAAKCAAMCAAOCAAACgACCgAECgAGCgAICgAKCgAMCgAOCgAADAACDA AEDAAGDAAIDAAKDAAMDAAODAAADgACDgAEDgAGDgAIDgAKDgAMDgAODgAAAAQCAAQEAAQGAA QIAAQKAAQMAAQOAAQAAgQCAgQEAgQGAgQIAgQKAgQMAgQOAgQABAQCBAQEBAQGBAQIBAQKBA QMBAQOBAQABgQCBgQEBgQGBgQIBgQKBgQMBgQOBgQACAQCCAQECAQGCAQICAQKCAQMCAQOCA QACgQCCgQECgQGCgQICgQKCgQMCgQOCgQADAQCDAQEDAQGDAQIDAQKDAQMDAQODAQADgQCDg QEDgQGDgQIDgQKDgQMDgQODgQAAAgCAAgEAAgGAAgIAAgKAAgMAAgOAAgAAggCAggEAggGAg gIAggKAggMAggOAggABAgCBAgEBAgGBAgIBAgKBAgMBAgOBAgABggCBggEBggGBggIBggKBg gMBggOBggACAgCCAgECAgGCAgICAgKCAgMCAgOCAgACggCCggECggGCggICggKCggMCggOCg gADAgCDAgEDAgGDAgIDAgKDAgMDAgODAgADggCDggEDggGDggIDggKDggMDggODggAAAwCAA wEAAwGAAwIAAwKAAwMAAwOAAwAAgwCAgwEAgwGAgwIAgwKAgwMAgwOAgwABAwCBAwEBAwGBA wIBAwKBAwMBAwOBAwABgwCBgwEBgwGBgwIBgwKBgwMBgwOBgwACAwCCAwECAwGCAwICAwKCA wMCAwOCAwACgwCCgwECgwGCgwICgwKCgwMCgwOCgwADAwCDAwEDAwGDAwIDAwKDAwP/78KCg pICAgP8AAAD/AP//AAAA//8A/wD//////yH5BAAAAAAALAAAAABwArcAAAj/AP8JHEiwoMGD CBMqXMiwocOHECNKnEixosWLGDNq3Mixo8ePIEOKHEmypMmTKFOqXMmypcuXMGPKnEmzps2b OHPq3Mmz50oCKAkIHQrUp9GjSJMqXcp0ZlGTTwdGbUq1qtWrWLPynDqSK1etYMOKHUu2bMKv /4gSVCt1qNS0U722FbrWrUCgdu2a3cu3r9+/Gr9GLTr47tq7ggs+LZz2MNy2bwFLnky58l60 jhNHRktUL2PFhiOHtky6tOnTOzGzfVyXLWeDhDu3Jux4NOrbuHPrDvnaNuvGsBHKBR489Gfi u5MrX85c+MHjm587B41cNPDjmJtr385dsmbWjMNPS89MHrFt6N3Tq18ftjNduHjnDvYs3P3s 1tdrV2fPv7//lwIE+N+ABBZo4D8BJnjgggw2qFyCAjoo4YQUAgahABVmqOGGWF3I4Ycghnm4 k4cilmjiiSqRiOKKLLaYkYouxijjjAjBSOONOLJoY4489sjhjj4GKSSDQA5p5JH8FYnkkkwy p2STUEZ52pNSVmnlX1ReqeWWYWXJ5ZdgMuVlmGSWOSKEZqapplFjrunmmyi1CeecdHokZ514 5knRnXr26adCfP4pXuiggQ5qqJ6FHqronIku6qiajT4qaZiRTmqplpVeqmmUmW7qKZKdfipq kKGOaiqOpZ6qaoypruoqiq2+KmuIsc5qq4a13qqrhLnu6uuBvf4q7H/BDmvsesUeq+x2yS6R 6+yDaD4r7Y/RTmsthc2S+d61rFbr6WrcupjtlfaFK+O4Ur6nl7nieruoZ9uy266C78YLn7wz oivkunPhm6+7etqLn7/nAkwnv4oJTPCK+s6IMGwKLwyrwWk+/FzEEp/Y8IoYX5xdxiVuXKLF Z3UMcsgUa0myQiufjDK9X7bMsskuiyhyhTQvJHPNtKa85M4zf9bM88sRRgl0yUIPbeLNBR5d snxKdwvzkTnrrK5+UTPs841Oe+zbfllrvHWMXUO8WNBnrwvuanglHTZuTHNXNsT3UWfc2cjR tpnbb+sWN3NzJ8zZtuJFV5xxfff3d3JVB81QbK7VZm/hiSc59oeB9/v413knbJ3elSt+eYaZ Q3a44XaDDXp+oRM7uoSlIybYZ5Szjjjqrfu3eGWNI4224HiPtjZ9uRO4O2Cxx148jcfzpXzv yw/ZPFnPQx+99K+zZ73Z15M5fVbJb9/9kd9XVf34kGa/XPV8jqMvZflJiT+w+2vC71P47dN/ pf064a9/nfyzyfn+h6cAyoR9BESU+ryTP68lsE8GZIn/HvinCAZFfqajoKAsSBIEatBQHORN A7n3QUWFsCMTLOGiTpiRAarwUSysiAdfKKkYSgSDsqOhpmzokBTq8FI8dNxFcPhDAC4wNURU XhGNODWqJJGIS8xTEO9lESWERlGBTTyKD694qhO6kIuu4uATRwhGGB5RJVss46vsl0Y1yqp8 4XOjsL6XOSvK0YxZhMnc7HjHGp5RhPnjYx8ndTynQXGQntod0ASJSCD+EYU0Y2Qjd/jIjaxM kpPcVNxIdshMqoppD8OkJz91M36JcpSiEhm8yIjKX20sL6xs5RwrSZFy3MlyYfoC1y1xScuI dHKXruwlMK83xWHeqphQco9bYmlMiyDTaM2cyTOZxMxodmSaVLPb8AgnuVP2EZv7ok7tVkdO a0YEnD2KC+e+YzuwmXMh6MSROs3jOf1AzpuTjKfDUvebDNbunc4U5rv4uc7zcA6gexKooeY5 TuGVE6EBzaOq5gmf+cRrmVDzSwA2ytGOevSjIA2pSEdK0pKa9KQoTalKV8rSlrr0pSYFgExl CtOa2vSmOM2pTndaUgbx9KdADapQh0rUnc60qEhNqlKXWlOfBgCiPtqoU6HaI6mzLsiqVMUR Vg201azOqKsEAqtXXSTW/5R1rCs6a3/UilYTsZU9b21riOKqHrrKlUN27U5e75qhvW7Hr3yd EGCbM9jANqiwy0GsYQ+k2J4o87GQjaxkZSrZylr2spjNrGY3y9nOevazoA2taEdL2tKa9rSo Te1mKWtaAap2sgB4rWxnS9va2va2uM2tbnfLW82ytrSLDa5wh0vcEz1WZwctLrfYWZxqKvdW zBXnc/31HbY5lJtIv5zuozRTuIdmV7vbVebnbvdP8P4KOt2VXV7MeyyKdo510WWvrtybXtXJ d1jDea/eyntfW1WXeIshXn8HTOACG/jACE5wuAICADs= --------------070904000707000304000604 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --------------070904000707000304000604--