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: µS/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" (sorry if the columns don't line up) The 10 uS one is of most interest to us. So, how could one make their own calibration solution without access to a precision scale? For example, knowing the distilled water temperature, could one saturate the solution with NaCl and have it be a predictable mg/L strength - then dilute it down to 4.3 mg/L? Chemists - what say ye? 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. -- 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]>
