Ya know, I just may have made an error. The Dist 1 does something like that and I found it curious but it didn't click. I'll have to recheck.
B'golly you be correct 199.9 it is. I stand redfaced before all and my horse considerably lowered. Perceptions are indeed a funny thang. Still don't mind doing some looking into how they do in the field on CS though. I'd actually be glad if they were right on. If I get two labs tests that are nearly the same, I'd be glad for that too. A least that would put the cow pie somewere where 'I' can toss it or toast it 'stead of just standing under the cow. Ken At 10:21 AM 10/31/02 -0800, you wrote: >Hi Ken, > >I've been too busy to follow the PWT accuracy thread with anything more than >casual interest. However, the Hanna technicians assure me the stated range >is what their accuracy is based on. > >Today I took 3 PWT meters and put them into distilled water. I then began >to add tap water very slowly and watched the readings rise over 99.9 without >going off scale. However when the reading got to 199.9 it then jumped to >1--.- So, if for sake of argument the accuracy is 2% of full scale, then >the most they would be off is 4 uS. But I think the factory is correct in >saying the accuracy is set by the range they specify rather than the total >reading the meter is capable of indicating. I believe it was Ivan who said >they are just using the most linear portion of the scale to use and the >over-reading capability is not to be considered at the same accuracy. > >Unless your meter is different than the three I tried, how can you get a >reading of 999.0 before it goes off scale? Perhaps your meter is not >working properly. Or should I try a few more meters to see if they all act >the same? > >I really don't see any problem since we're not trying to measure anything >near the upper limits. We're talking about the range of 5-20 uS in most >cases and an occasional foray into the 30-40 uS area. I think they work >just fine. And the ones I use are always in agreement. I always use 3 >meters when calibrating our SG7's to make sure we get them properly >adjusted. > >This seems like beating a dead horse to me. > >Trem > > >----- Original Message ----- >From: "Ode Coyote" <coyote...@earthlink.net> >To: <silver-list@eskimo.com> >Sent: Thursday, October 31, 2002 10:49 AM >Subject: RE: CS>TDS/PWT meters > > >> I'm willing, out of curiosity, to 'determine some idea' of how far off >> reality is from various stated views of it. [something within a range in >an >> infinite scale] >> I've got an odd feeling that no one can say anything that's true about >> anything. [Nothing that is, except, perhaps, that statement.] >> >> So, maybe an average standard will do? [along with an illustration that >> that's all we ever had anyway?] >> >> >> The PWT actually has a 4 digit display and pegs out at 999.x uS just >> before it shows a 1 in the far left saying it can't read that high or any >> higher. >> The DIST 1 [much similar to the TDS1 I presume] will read up to 1999 PPM >> before the last 3 places vanish leaving a 1 in the far left place to >> indicate it's beyond capabilities. Range is stated as 1990 PPM >> >> [all regardless of accuracy issues or what or how anything is written, >> these are the actual facts based on doing and seeing it.] >> >> My problem with all this is that accuracy is based on full scale without >> any clear indication of what full scale 'is' even if [especially if] full >> scale is not "as high as it will read". Nor are there any indications >that >> there is more than one scale. >> If they had based accuracy on the intended range within any scale or >> numbers of scales, I'd not even have a question. Who cares what it reads >> beyond it's intended range? But when you base accuracy on scale and then >> don't say what the scale is, leaving you to assume it's something like the >> stated range, but turns out not to be even close and they don't make any >> attempt at all to qualify the possible differences in perceptions and go >on >> to write a specification based on an undefined quantity...I tend to wonder >> what the heck they said or if anything was. It smacks of double speak fit >> for a politician. [or salesman...same motive of persuasion] >> >> Have you seen the negative political ad where the written words say "... >> took $40,000 from sons college fund to buy a new car" [implying that she >> ripped her son off] and the vocals say "..Took $40,000 out of sons >> college fund because 'he' wanted a new car..and slurred the 'he' part just >> a little to sound a little like s-he" ? >> Double speak and misdirection. Manipulation towards a point of view >that's >> not true but done without actually lying. >> The FDA reports on colloidal silver are chock FULL of that sort of thing. >> Why? >> For instance..."not proven safe or effective" does not mean "proven >> unsafe and ineffective", but that's the impression that one gets from the >> reading and phrasing of a collection of studies that have the title >> "Colloidal Silver"...when not one single study within the report even >> mentions colloidal silver. >> One may as well compare a Volvo to rust because they both contain iron, >> then say whatever you want to about Volvos because iron is strong or rust >> is stable. Is it a true statement that rust can't rust, so it's rust >proof? >> I've had "dependable" Datsuns that ran till there was nothing left to >> hold the wheels on..in only 10 years. Well, it ran extremely dependably >and >> still does, but you can't drive it. Toyota fixed the rust problems but >> screwed up the motors by replacing a $12 steel part that never fails with >a >> plastic one that tears up the entire front of the motor and contaminates >> the oil which burns up the bearings, rings and cylinder walls when it goes >> out. I drive a 1985 Toyota with a 1978 motor in it. They both died from >> different diseases so I did some grafting. We won't even get into Ford, >> Crysler and GM. {AMC?? Yea, right...no two alike} >> >> Never-the-less, we still use automobiles and they serve us adequately. >The >> ambiguities can often be worked around to make something that's actually >> good in all respects. The manufacturers won't tell you what fits what with >> whatever modification or what's weak. [Just don't asked me what year, >model >> or brand my car is 'cause I'll have to ask you which part?] >> >> My lastest in progress is a Hondumpharly motorcycle. The Triumaha works >> good as did the 1968 thru 1990 510610810620720280240z L/z series >> Subavolksadasun! ;-) >> >> "More doctors recommend this drug over all others combined" OK, what >> doctor would recommend combining all other drugs? The statement is true, >> but does it say what it says? LOL >> >> Maybe, just maybe, we can get doublespeak [our only language] to talk more >> true than false for a change and in one instance. >> Ken >> >> At 01:31 PM 10/29/02 -5, you wrote: >> >Ivan and Ken, >> > >> >You're exploring the issue of accuracy and precision of the Hanna PWT >> >and TDS quite thoroughly! But let's see if I'm misinterpreting you >> >right on a couple of points... <grin> >> > >> >Specs for my Hanna TDS-1: >> > >> >Range: 0 to 999 ppm >> >Resolution: 1 ppm >> >Accuracy: +/- 10 ppm >> >Typical EMC Deviation: +/- 1% of Full Scale >> > >> >If I interpret this right, my TDS meter should read in steps of 1 ppm, >> >with no decimal point or tenths, etc., which indeed it does. >> > >> >That means the smallest increment it can *resolve* is 1 ppm. >> > >> >The display, with 3 digits, will show from 0 to 999. >> > >> >The accuracy of 10 ppm out of a full scale range of 1000 ppm is, indeed >> >1%. >> > >> >I don't know what "Typical EMC deviation" means. What's EMC? >> > >> >It's pretty clear why the TDS-1 isn't the best tool for measuring low >> >ppm CS. I'm attempting to use ruler where a vernier caliper would be >> >better. Still, it's been stable and seems more accurate than spec. >> > >> >So what are the specs for the PWT? >> > >> >From: http://www.hannainst.com/products/testers/pwt.htm >> > >> >Specifications: >> > >> >Range: 0.1 to 99.9 µS/cm >> >Resolution: 0.1 µS/cm >> >Accuracy (@20°C/68°F): ±2% Full Scale >> > >> >This suggests that the smallest step this instrument can resolve is one >> >tenth of a micro-Seimens per centimeter, and it can count up to a >> >thousand of them, or 99.9 µS/cm. So I presume the display should show >> >only 3 digits, one to the right of the decimal place. >> > >> >However, Ken writes: >> >> It says "Range is .01 to 99.9 uS" and "Accuracy is +/- 2% Full >> >> Scale" [but don't mention what full scale is] Now, you'd think that >> >> range and full scale would be the same thing, BUT, stick the PWT in >> >> water and add salt to see where the scale ACTUALLY pegs out. That >> >> would be at 999.9 NOT 99.9. If the meter were accurate to +/- 2% in >> >> its "range" they would have said it that way. >> > >> >It looks like Ken made a small mistake about the low end of the range. >> >That aside, does the PWT actually have a 4-digit display and behave as >> >Ken describes here? It *should* have only a 3-digit display and top out >> >at a reading of 99.9 uS. >> > >> >Whatcha say guys? >> > >> >Be well, >> > >> >Mike D. >> > >> >[Mike Devour, Citizen, Patriot, Libertarian] >> >[mdev...@eskimo.com ] >> >[Speaking only for myself... ] >> > >> > >> >-- >> >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> >> > >> > >> >> >> > >