Hi Grant, We take the final reading, subtract the initial water reading and multiply by 1.2. For more accuracy it's best to wait 24 hours because the ionic content will drop during that time.
I usually just take the initial PWT reading right after the unit shuts off and it is plenty close enough without having to wait and then apply the correction factor. Remember, this isn't rocket science and close is plenty good enough for most folks. Trem ----- Original Message ----- From: "Grant" <g...@island.net> To: <silver-list@eskimo.com> Sent: Thursday, May 30, 2002 9:49 AM Subject: Re: CS>TDS-1 versus PWT for measuring PPM > Sorry Trem: > What I meant was what is final formula for the "PWT", not > the TDS-1.. > Tks Grant.. > > Trem wrote: > > > > Hi Grant, > > > > I really don't know since we will not sell them. I bought one years ago > > thinking it might be the unit to use and provide to our customers but soon > > after discovered the PWT meter was the unit of choice. > > > > I just took the average of 3 PWT readings of some CS that measured 20 uS > > (water was 1.6 uS so total PPM was 22) and measured it with the TDS-1. It > > measured 7 so guess I would multiply by 3 to get the same PPM as the PWT. > > > > Of course I have no idea if the TDS is reading correctly but if it is then > > the correction factor would apply to anyone else's TDS meter when measuring > > CS with the same ionic content as our CS. > > > > Hope this helps. > > > > Trem > > > > ----- Original Message ----- > > From: "Grant" <g...@island.net> > > To: <silver-list@eskimo.com> > > Sent: Wednesday, May 29, 2002 8:20 PM > > Subject: CS>TDS-1 versus PWT for measuring PPM > > > > > Hi Trem: > > > ` So what's the final formula for the TDS 1??? > > > `Is it half the pwt reading plus 20%.?? > > > Tks.. Grant.. > > > > > > > > > > > > *********************** > > > Hi James, I don't mean to jump in when you addressed the post to Dean > > > but the fact is that the PWT reads CS much better than the TDS-1 for > > > several reasons as pointed out on our website. Also, you do NOT divide > > > by half when using the PWT. You ADD to the reading. In the case of our > > > generators you add 20%. Hanna is right in telling you to cut the > > > reading in half IF you're measuring dissolved solids such as minerals in > > > the water. However, we as CS users are interested in measuring the > > > content of CS to determine what silver content we have. In this case > > > the meter only measures the ionic portion of CS. And that reading is > > > always less than the total amount of silver content because the meter > > > will NOT read the colloidal portion. Therefore one has to add to the > > > reading to get the total PPM. The correction factor will be the > > > difference between how much of the mix was colloidal versus ionic. We > > > have had our CS analyzed by atomic absorption spectrophotometry and it > > > is generally always the same ratio. Another thing I forgot to mention is > > > the fact that the TDS-1 has an accuracy tolerance of + - 2% of full > > > scale. Since the TDS-1 reads from 0-999 that's + - 20 PPM. Since the > > > PWT reads from 0-99.9 and has the same percentage of accuracy that's + - > > > 2 PPM. And the PWT gives you a decimal point in the reading while the > > > TDS-1 reads in whole numbers only. I hope this helps clear up some of > > > the controversy about the TDS-1 versus the PWT. The PWT is the best > > > choice hands down for measuring PPM.T > > > > > > > > > -- > > > 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> > > > > > > > > > > > > > > > >
