----- Original Message ----- From: "Tony Moody" <[email protected]>
Hi Tony, Thanks for your reply. > Ivan, > I guess the complication of using a calibration solution is to cater for > any oxidation on the probes faces or to account for the probes not being > the exact size and distance apart. There must be some reason. > This circuit uses a 10kHz rectangular wave oscillator which is high > enough frequency to prevent electrolysis. DC voltage or current would > distort the measurement. You're right... the use of a calibration solution is to compensate for the discrepencies in the sensing mechanism, and it makes sense to calibrate in a solution similar to the one you are measuring, but I have calibration solutions in silver nitrate, potasium chloride and sodium chloride, and have found that the precision resistor to be spot on. That may well change over time I suppose, but for the purpose of reading the concentration of CS, which is different from the theoretical measurement of Ag+ ions by some margin (although repeatable from batch to batch) some mis-calibration would not matter much. > A 555 chip powers a resistance bridge (including the unknown > conductance) which feeds a TLC272 opamp with feedback to give X10 > amplification, signal is then high quality rectified with the other > TLC272, buffered with another one and pumped through a 50uA meter for > indication. > > BTW They talk of using two pins from a print header, preferably gold > plated, for the probes. Also talks about a fixed distance apart but not > an enclosed volume. > > Tony Is there a link to this circuit? Regards - Ivan -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: [email protected] -or- [email protected] with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
