Paul has led you astray a bit in his answer :-) Both the TDS (total dissolved solids) meter and the PWT (pure water tester) are conductivity meters. The difference is in the scale and calibration. A TDS meter is calibrated to convert the conductivity reading (micro-Siemens uS) to reflect the amount of dissolved calcium carbonate (in most cases) that would give rise to the conductivity measured. This calibration is about 1ppm TDS to 2uS for CaCO3. That would be fine if one could just multiply the ppm TDS x 2 to get the equivalent conductivity reading in uS, however, most TDS meters have a scale 000 - 999 ppm TDS, and generally have a error of 2% of the full scale reading. The error is therefore +/- 20ppm TDS or a range of 80uS, obviously too high if one is measuring a 10ppm CS solution which will have a conductivity reading of about 8uS.
The PWT scale is much more suitable, being 00.0 - 99.0 and the readout is in uS. The error is +/- 2uS or a range of 4uS. Regards Ivan. -----Original Message----- From: kaselo...@aol.com [mailto:kaselo...@aol.com] Sent: Saturday, 26 October 2002 1:52 p.m. To: silver-list@eskimo.com Subject: CS>TDS/PWT meters please explain to me as simply as posible the difference between the tds meter and the pwt meter when testing CS... we have two tds meters, and they both give totally different readings... if i understand correctly, i need to invest in a pwt meter but i'm not totally understanding why it is better... thanks! -- 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: silver-list@eskimo.com Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <mdev...@eskimo.com>
