Taken from a communication with "Stuff" Check me on this Trem. Make sense?
I've studied long and hard on the problems with calibrating a PWT. I "thinks" I've got it. The major problem is misunderstanding what the limits of temperature compensation are and what it does. Hanna doesn't exactly explain anything. The next, but probably more rare, is the quality control over the solutions. I got a bottle that was off by 50% The meters are factory calibrated. They used to be 'certified' but they no longer include the certificate. Shipping 'could' throw it off but it's not likely. My 2 PWTs bought almost 4 years apart read almost exactly the same. So Here's the procedure as far as I can figure. 1] Let everything sit for several hours in the same spot so everything is at the same temperature. 2] Rinse your container out with distilled water and shake reasonably dry. I use a baggie. I've tried a metallized plastic sachet as supplied and instructed and it sucked out loud. The reading never stabilized. [But then, I might have been warming it in my hand. Metallized plastic is more thermally conductive than a glass] 3] Insert the PWT in the solution. Do not warm the solution by touching the container where the solution is. Take a reading of the factory setting for reference. 4] Ignoring any and all temperature adjustment instructions and charts, adjust the meter to 84 uS [or whatever the solution is supposed to be] if it already isn't there. If it's WAY off...get a different batch of calibration solution. A change in temperature of the solution...but not the meter.. WILL throw the reading off. The temp compensation of the meter has to have to do with changes in meter temp, not solution temp because the mass of the meter and location of sensors has to indicate a very long stabilization time where both the meters mass and the mass and thermal conductivity of the solution will take a long time to equalize the relative temperatures making the readout unstable for several minutes. This is probably why the reading drops steadily as you measure warmer CS water. The cool mass of the meter cools the CS as the CS warms the meter. [and that's not considering any stratification of conductivity in the water or the effect of the AC signal on the CS as the meter is being used] If you hold a baggie of calibration sol warming in your hand, the readout will steadily rise and the rate of rise varies from meter to meter. If both are at the same temperature, the readout stabilizes within one or two seconds. Of course, CS is much more weird than the calibration solution but that experiment tells a story about what the temperature compensation does, what the limits are and why. At 07:44 AM 11/9/2003 -0600, you wrote: >Got my Hanna PWT yesterday and calibrated it with the solution and checked >my IW: > >.9 uS x 1.5=1.35 ### That's "PPM" of the water using water industry standard fudge factor? > >Checked a clear batch and got 17 ppm ### Was that uS or the PPM after applying the formula? 17 uS x 1.2 [fudge factor]= 20.4 PPM. [minus 1.35 PPM of the water = 19.05 PPM silver] That's in the ballpark..checked when freshly made too, right? A better way... 17uS - .9 uS = 16.1 uS X 1.2 = 19.34 PPM Or if it was 17 PPM and not uS... 17PPM / 1.2 = 14.16 uS - .9 uS = 13.26 uS X 1.2 = 15.9 PPM > >Checked a light yellow batch and got 14 ppm. ### The reading normally drops after particles form by as much as 50% though it's usually just 3 or 4 uS. This is because particles don't conduct electricity unless they touch each other and if they did, they wouldn't be in the water...they'd be on the bottom. > Is it normal to get a lower ppm with yellower batches? ## The color of the particle shouldn't matter except as a possible indication that more ionic silver converted, with some of it as slightly larger particles. [ Well maybe it does, but since I can't seem to make yellow batches unless I change the generator, I have no way to correlate it] Pale yellow indicates many many more small than large, so it's still very good CS. A yellow particle is still small enough to pass through a membrane. TE is a better indicator and yellow CS usually has a stronger TE. But looking at TE doesn't give you any numbers. [Very subjective...like, how heavy is heavy?] Ode -- 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]>
