Mike, I wont argue with your position. The problem comes in when a person starts to believe tht they are actually measuring ppm and tell others what their system will do and produce. You nailed it with the statement about a very narrowly defined situation.
If a person does their testing and recordong of data for a particlur set of parameters then if they have the CS measured the reading will mean something to them only!! It will repeat and could be considered a third order standard. It might be of value to put a short paragraph in the FAQ section about ppm measurements that you send to every newbie. Robert M. G. Devour wrote: > > Simon, > > > > Leave the TDS1 meter alone it is not an instrument to meassure ppm. > > The name implies Totally Dissolved Solids and CS IS NOT a totally > > disolved solid. > > I want to provide a *little* bit of balance to Bob Berger's comments. > > The Hanna TDS-1 meter is a *conductivity* meter that features > temperature compensation and readout in equivalent ppm of (I > believe) a standardized calcium chloride solution. It will give you a > reading that is ENTIRELY a function of conductivity. That is *ALL* > that it does. > > In fact, the better instrument of this kind for our purpose would be > the Hanna PWT (Pure Water Tester) which is essentially the same > instrument as the TDS-1, with more sensitive electronics that are > better matched to the conductivity range of our usual samples. > > It reads out in microSiemens which is a unit of conductivity. So the > PWT provides a more direct and honest result than "equivalent ppm > of a standard solution of some particular salt." It would be a lot > harder to decieve yourself into believing that you're somehow > directly measuring true ppm. > > TO THE EXTENT that conductivity can be *related* to the actual > concentration of silver in a particular sample of CS, both of these > Hanna devices will give a good, stable, and repeatable measurement. > > We do not know *HOW* conductivity is related to concentration across > the many possible variables of CS production. > > But, it is my contention that you can evolve a calibration curve > specific to a particular, very narrowly defined set of conditions. > It will only be accurate if you keep your setup and procedures > consistent and stay within the range of concentrations you have > VERIFIED BY OTHER METHODS. > > BOB B.: Do you agree with what I've written so far? If not, it would > be very good to know what you disagree with and why. > > I use my TDS-1 to test the quality of my distilled water. I also use > it as a simple cross check against my current readings to decide when > to stop a run. > > I *know* that all I'm seeing at this point is that my CS has the same > conductivity as an X ppm solution of a given salt. > > But I *also* know that the reading relates well to the concentration > of silver I got on my *last* batch, *and* on the batches made with > that same recipe on the same equipment that I had tested by Bob, or > my local environmental lab, or any other sources of proper analysis > services. > > > I suspect you are new on the list. The peole to ask are Ivan, James > > Holeman, brooks bradley, or myself. > > Bob, you and the others you listed are among the technical elite of > this list, I agree. I don't think you really want to exclude all the > rest of us from consideration, though. There is always room for > debate, here or there, isn't there? I hope? > > Also, I would never blame the newcomers for what they don't already > know when the information is just not available elsewhere! They're > not stupid, or they wouldn't be asking questions! > > > When I first got on this list the TDS was a great item, but I have a > > spectrophotometer for measuring ppm. So I bought one to debunk the > > whole mess. IT DOES NOT WORK. > > It works very well doing the job it was designed for, which is > interpreting *CONDUCTIVITY* into some standard unit of measure. > Correlated with Bob's spectrometer readings or the other standard > measurement techniques, it *can* give an approximate measurement of > "ppm" over a very narrow range of conditions and concentrations. > > By itself it can be *useful* to assure repeatability between batches > and even stability in storage. You just cannot really say what "ppm" > you have unless you've done the additional work of getting your CS > tested by other means. > > I'm not trying to encourage or discourage anyone from buying one of > these devices. I just want everyone to understand what they *are* > good for. > > Be well, > > Mike D. > [Mike Devour, Citizen, Patriot, Libertarian] > [[email protected] ] > [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: > [email protected] -or- [email protected] > with the word subscribe or unsubscribe in the SUBJECT line. > > To post, address your message to: [email protected] > > List maintainer: Mike Devour <[email protected]> -- 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: [email protected] -or- [email protected] with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: [email protected] List maintainer: Mike Devour <[email protected]>
