url: http://escribe.com/health/thesilverlist/m60187.html CS>Calibrating your PWT From: S & J Young Date: Fri, 13 Jun 2003 19:45:34
> Greetings, > Recently there have been postings regarding PWT calibration. On a > CS website is a table showing the mg of salt in a liter of water > to produce various readings: "The following table shows a typical conversion of the PWT readings: uS/cm Reading Resistivity mg/L of NaCl 99.9 10 Kohms 48 10 100 Kohms 4.3 1 1 Mohms 0.4 0.1 10 Mohms 0.04 > Scheme #2: The PWT meter comes apart fairly, easily exposing the > two connections to the electrodes. So it is easy to bridge those > connections with a precision resistor and note the digital display > reading. I tried that using the resistor values above and did not > get the readings shown above. So I am wondering if the sampling > volume is not one cubic cm and Hanna scales the reading to make it > as though it was exactly one cubic cm? If that is the case, then > does anyone know the correct test resistance (actually reciprocal > resistance, mhos)-to-display factor? > Thanks, > Steve Y. Steve, this is probably the most valuable post of the year. There have been other posts on calibrating the Hanna with a resistor, but they encountered problems getting access to the electrodes. You have taken it one step further. Bravo! The resistor method is probably the most accurate, and can be verified with any 3 1/2 digit dvm. This gives independant traceability, so there can be no question about the results. It should be possible to make a table of resistor values that cover the entire ppm range of interest. I sure hope someone knows the Hanna sample volume and can supply the needed conversion factor. Best Regards, Mike Monett -- The silver-list is a moderated forum for discussion of colloidal silver. Instructions for unsubscribing may be found at: http://silverlist.org To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
