T.D.S. Meter ????

[NaCl_H2O]

I have a Kent RO/DI unit with a dual TDS meter - I have had it a little over a year. The output reading has been climbing a little and a few days ago the output reading jumped to 100 ppm :shock:. So, I figured it was time to change filters - I even bought a new membrane just to be safe (I filled my 500g+ system with this ... and my SPA :-D)

Put in all the new filters AND the membrane ... still reading 100ppm on the output :evil:

So, I took out the TDS probes and cleaned them (they looked fine?). While cleaning I noticed the "IN" probe reads "000" when it was dry, and the out read "120" when dry :wtf:

So, I put the IN probe in the OUT hose & vice versa - so at least now I can "believe" I have 000 ppm output ;)

So, finaly the question: TDS meters have batteries :idea: how do they "act" when the batteries are getting low? Could this be the problem, or do I have a probe that has gone bad?

Thx - Steve

[NaCl_H2O]

Since it isn't reading "000" when dry, I'm going to try the batteries too?

It can be calibrated, suggested I use 0.5mS, 342ppm Cal fluid?!?! Can't find that anywhere with Google?

GaryP - Got any 342ppm NIST standards laying around ;)

[GaryP]

Steve,

Sure I have a gallon in my back pocket. I think there is a DIY standard somewhere on RC or elsewhere. Let me take a look in the AM.

Another option is to use tap water as a standard. SAWS publishes thier TDS data on their website. It may not be a super accurate way, but good enough for a qualitative yes/no answer on whether your meter is working properly. SAWS says the TDS range is from 283-358 with an average of 321 ppm.

Gary

[captexas]

Definately check the batteries. If they are on 24hours a day, they may be low in power. As with Josh, my ph meter had all kinds of weird readings when its batteries were low.