Paul Bembower wrote: > I talked to a gentleman named Pete at Hanna Instruments in Rhode > Island, and told him exactly what it is I'm trying to do with CS, > and what range of PPM I am trying to achieve.
Sounds like a good plan so far! <GRIN> > He originally had intended to suggest the $15 TDS-1 or the $46 > DiST-WP1, but upon further reflection he suggested what they call > the PWT. It has a range of 0-99.9 uS/cm (micro-Siemens). 1 > micro-Siemen/cm is equivalent, Peter says, to 2 mg/l or 2 ppm. I'm with you this far... > So, you could use this instrument, which has an accuracy of 2% of > full scale (or 2 uS/cm) on CS with an actual TDS of 12ppm, and get > a reading of 22-26 uS/cm. Is this correct, Paul? A sample of 12 ppm would measure 6 uS/cm, wouldn't it? That would mean a reading of 4-8 uS/cm or 8-16 ppm. > This number is easily and, perhaps more accurately, translated > into a reading of 11-13 ppm, an accuracy of +/- 1 ppm. If 1 micro-Siemens/cm equals 2 ppm, then 2% of full scale would be 2 uS/cm or *4* ppm. Or put it another way, it is the eqivalent of a 0-200 ppm TDS meter, with accuracy of 2% of full scale, or 4 ppm. In any case it *IS* much more accurate than the TDS-1, 0-1000 ppm with 1% accuracy (+/- 10 ppm), or the DiST-WP-1 with 0-2000ppm, 2% accuracy, (+/- 40ppm !?). I'm beginning to believe these meters from Hanna are based on only a couple of different circuit boards, re-calibrated for each application. Nice marketing! > Further, Hanna can supply a calibration solution for $8.40/460mL, > which, if properly cared for, could last for a very long time. The > calibration standard is at 84 uS/cm, which is 42 ppm, and is much > closer to our range than anything we could manufacture reliably > ourselves. I'd really like to know if I could use that solution to calibrate my TDS-1? That would be good enough as far as I'm concerned. For that matter, could you crank the calibration screw on the PWT far enough to let it read ppm directly, and would that be reliable? > Before I spend anything on this, I'd like to know > what some of you think of this. > > You can look at this on-line at: > > http://www.hannainst.com/products/testers/pwt.htm"; > I just want to be sure that when we mention a TDS reading, whether done on a TDS-1, DiST-WP-1 or PWT, we're all going to get close to the same measurement, whichever tool we're using. Thanks, Paul. This is an important thing to figure out. I think it's time I talked to Hanna, too. You got us onto a good path. Be well, Mike D. [Mike Devour, Citizen, Patriot, Libertarian] [mdev...@mail.id.net ] [Speaking only for myself... ] -- 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: silver-list-requ...@eskimo.com -or- silver-digest-requ...@eskimo.com with the word subscribe or unsubscribe in the subject: line. To post, address your message to: silver-list@eskimo.com List maintainer: Mike Devour <mdev...@id.net>
