What comprises that "190 ppm?" And is that an actual 190 parts per million of dissolved solids, or just a
wild-add guess calculated number arrived at by a "TDS" meter that actually just measures the EC of the sample and then multiplies it by a "conversion factor" to give you an answer that its manufacturer thinks you will understand better than if you were given the actual EC (electrical conductivity) amount - which is the only thing that is actually measured?
Example: Device measures actual EC to be .6 ms/cm. Milwaukee, Hanna, and some other "TDS" meters will display 300 PPM. Eutech (and some other) "TDS" meters will display 384 PPM. Truncheon (and some other) TDS meters will display 420 PPM. Which ones are showing you the correct reading?
None of them. Unless, that is, you happen to be measuring water that has only
ONE solid dissolved in it, and that one happens to have an EC value that matches that particular meter's conversion factor. Otherwise, well... It can tell you that, when you put more stuff in the water... that you end up with more stuff in the water
.
A friend worked at a municipal wastewater treatment plant. As part of his job, he had to record
actual TDS amounts a few times each shift. I used to go over there when he was working by himself to borrow the use of the lab for... various things, and I was impressed by the amount of money tied up in the equipment there. Among many other things, there were several different continuous duty pH measuring devices. I got curious and looked up the price to one of them, thinking that it was undoubtedly a good one, and that I'd like to have one that I could just set up with its probe in my reservoir and be able to read/log the numbers at will. I forget the exact dollar amount, but it was in the neighborhood of $3,800 - and I checked the price on that one because my buddy mentioned that they'd wanted yet another backup, so ordered "a cheaper one" (meaning it), lol. So, anyway, you'd kind of expect them to have the best tool for the job and all that, right? That, when they had to measure the amount of total dissolved solids in a sample, they'd be able to use some fancy, expensive device, take a sample and stick its probe in it...
Nope. Oh, they took a sample. But then they put it into a pre-weighed container, flash-boiled all the water out, and weighed what was left on a very accurate (one ten-thousandth of a gram or one hundred-thousandth of a gram, I forget which) scale. Thing was so accurate, in fact, that it had to be placed on a very solid/heavy table, on a solid floor, and inside a glass case. The table was marble, granite, something like that. The glass case was so that the air currents in the room wouldn't cause the reading to change.
They knew exactly how much stuff was in their sample that way. But they didn't know exactly
what was in it. They did know that it was a combination of things - and that's why they couldn't simply use some kind of meter.
All those "TDS" meters can do that common sense cannot (see above), is give you a rough idea of how much stuff your plant consumes.
Rough, because a high consumption of one element might change your meter reading by exactly the same amount that a lower consumption of a different element might. (And we all know that plants do not consume only one element at a time.) Also, because the things only measure EC, anything that does not cause the EC of the solution to change cannot be measured with one in the first place.
BtW, you can measure EC with a DVOM
. See:
Answer (1 of 5): At best, you can estimate the conductivity of water using a multimeter. There are two methods. WARNING: DC current in water creates electrolysis—the conversion of water into it’s two parts, hydrogen and oxygen. Large batteries will create large amounts of hydrogen and oxygen gas...
www.quora.com
Take a look at your water supplier's annual water analysis / water "health" report. That will give you an idea as to what's likely to be in your water (although there will be some seasonal/etc. changes, and your pipes may contribute some small amount).