There are ultrasound meters to detect liquid levels En Wed, 31 Aug 2016 12:41:41 -0300, Eoin Ross =20 escribi=F3: > Capacitive sounds like the ticket to me > > http://www.analog.com/library/analogdialogue/archives/46-05/cdcs_in_healt= hcare.html > > Eoin > > > On 2016-08-26 6:34 AM, James Cameron wrote: >> Living in the outback ... >> >> Looking for a way to estimate liquid levels on the other side of 4mm >> plastic; a potentially flammable methane-air atmosphere, without >> necessarily cutting holes in the plastic. >> >> Composting toilet collection bin has a coarse filter 50mm from the >> void at the base, and a liquid drain. A DC fan pulls air through the >> bin contents, through the void, into a chimney. >> >> Composting works best when the void has less than 20mm of liquid. >> >> Sometimes the drain becomes blocked. >> >> Liquid levels increase slowly, blocking the airflow, until the gas >> generation of the bin contents exceeds the airflow, then the residents >> really notice. Pong. >> >> How to measure the liquid level? >> >> Float switches would become fouled. >> >> IR reflectance sensors would be great, but expensive, and if covered >> by muck wouldn't reset until the bin was serviced. >> >> Stainless steel bolts through the plastic might work, but there's a >> conductive path through condensate on the inside surface. >> >> "Can't you just point an instrument at the tank from the outside and >> have it tell you the liquid level?" ;-) Magic is wanted. >> > --=20 Usando el cliente de correo de Opera: http://www.opera.com/mail/ --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .