I shopped off amazon and they have one for $54 I believe. But a couple people off here told me to get PH tape. I also got that off Amazon, and you have to be careful because there are different types, so you want to make sure to get the one that reads the correct area. (I think the one I bought was 4.0 to 9.0 although you can get it to read the whole spectrum, I thought this might be more accurate, and some only read to 4.0 and so on.)

Hope this was a little help!

I'm sorry, but it won't help me if you only tell me where to get them. I knew that much as well as the scale system. But I still don't know how to use it, or if I need it at all for plants growing in potting mix. Perhaps a simple pH tester would do?

simply put EC and TDS is a measure of dissolved solids in water. pure water does not conduct electricity. As you add more and more amounts of compounds (i.e. dissolve them in water) your water will begin to conduct electricity. An EC or TDS meter measures how much electricity is being conducted and the hydroponic gardener can use that to decide how much nutrient is in his solution.
The Electrical Conductivity (EC) of a liquid is measured in μS/cm (micro siemens/centimeter), so a EC measurement is an actual reading of Conductivity. TDS on the other hand, reads the EC and multiplies it by a factor (typically 500 or 700) to generate a ppm readout. If you know the conversion factor, you can easily divide by that to get EC. However you should not state ppm as measured from a TDS meter in forum discussions because we don't know your conversion factor and ours (if we use them) may be different.
The best way to use an EC meter, IMO, is to first test your plain water and record the EC(if there is one). Next mix up a nutrient solution, preferably with a know total disolved solids concentration, and measure and record this EC. subtract the water EC from the nute EC, and you have the EC of your nutrient concentration.Now you check the EC level of your rez every day and if the EC is increasing, your plant is using more water than nutrient. if it is decreasing, it's using more nutrient than water. Based on the difference of a particular reading to your total reading you can add more nutrient to your solution to bring the EC back to its initial EC reading (or add water to drop it or both if it is balanced and the rez is low)
You still want to change out your entire rez occasionally because with time, the plants will use more of one mineral than another and so your EC reading may be steady, but you'll start to have deficiency in the nutrient solution itself.
That's by no means a complete discussion on the issue, but its enough that you should understand what they are and how we use them. Also, all my comments are specifically directed towards hydroponic gardening. In other applications , things may be different.
BTW, I use a truncheon EC meter and a pH meter I bought from aquatic ecosystems for $18 about 5 years ago. I am fortune to have good water currently and so I don't test pH nearly as often as others on here must.

grizzman...you're my hero. Thanks for explaining that in such easy to understand terms! I can read it a hundred times and I don't always get it. Even though it wasn't for me, I appreciate you posting that!

igrowindoors, I'm sorry I wasn't any help :/

Would like to add and correct a few things here:

1. Pure water without any dissolved solids does conduct electricity pretty well, (try to put 110 or 220 volt in recipient with 100% pure and distilled water and put your hand in there!) the difference is that, the more dissolved solids that are dissolved in the water, the higher the conductance of the water.

2. Lots of talk has been done about PPM conversion rates that are based on electrical conductivity EC reading of mS/cm but converted to various PPM rates, mainly 500 or 700. Do they correspond to actual PPM of any nutrient solution, or not, are they related directly or not, how comes etc. I guess many people haven't understood why and how it is. It's simple: The actual ppm value of a specific sodium chloride solution is very close to half of its conductivity value (in microSiemens/cm), That is why these "TDS" meters display the conductivity as an equivalent NaCl amount (1000/2= 500). The 700 conversion rate is derived from a specific potassium chloride (KCl) solution instead.

Important: both ppm readings of either conversions used here are not related directly to YOUR or ANY nutrient solution or their actual and total PPM content in all elements. Hence, never think that a ppm reading of any TDS meter expresses any actual ppm of your formula or solution nor can be compared to any ppm recommendations for single elements as in N= 180 ppm, or P= 250 ppm etc.

BUT it happens that the reading of a 500 conversion rate TDS-meter is quite close to most nutrient solutions, generally the reading is 10-25% higher as the actual content in ppm. It varies with components used as in the actual composition of the nutrients. Fortunately or unfortunately, however - do not confuse the ppm reading of any TDS meter with the exact content in ppm of elements in your nutrients or the total dissolved solids it contains.

3. As for the use of ppm readings and data (of a so called TDS meters), you may pretty well state ppm readings and data in forums as long as you know and TELL the conversion rate that goes with it as well.

Well put my man! Thank ya both grizzly and lucas. Now I know that it is practically pointless to get a TDS meter! Haha! Unless of course it is cream of the crop and can figure out the exact elemental composition of my nutrient solution as well.. (which is highly unlikely). I know that the 500 conversion can give you a decent rough estimate, depending on what your definition of decent is haha, but for me even a margin of error ranging from 10-25% is too inaccurate for me to deem useful!

Again thanks for both of your comments! I hope your learning from these guys igrowindoors!

>>Unless of course it is cream of the crop and can figure out the exact elemental composition of my nutrient solution as well.. (which is highly unlikely).The fun part here is that there are TDS meters which enable you to adjust to a precise conversion rate instead of having a fix rate (500 vs 700). So, if you know all ingredients and their proportions in a solution and on top of that their individual conductivity, you actually can adjust and set your meter to the actual (result of quite a bit of calculus) conversion rate and get an (almost) accurate and true ppm reading - and hence the actual total dissolved solids of your solution! Well, you will never reach a high precision here, but get very very close though.

Then again, you can only know the ingredients and components used, if you compose and manufacture your own nutrients (unless the manufacturer releases these data - which is highly unlikely). In case you compose your own nutrients (as I do) you actually are supposed to know the actual dissolved solids of each component and hence the total in your formula. So this is kind of a causal paradox at the end: to be able to measure actual PPM with a sophisticated method you need some kind of information. If you have that Info, there is no need to actually measure it eventually. If you need (would like) to measure actual PPM, you probably haven't got the info - and hence you can't proceed... LOL

"If you have that Info, there is no need to actually measure it eventually."

Haha... wait, wait, the key word here is: 'eventually' lol.

..This seems like a rather sneaky and despicable way for business owners to capitalize and make money! We should all be outraged!

Wait a minute.....".This seems like a rather sneaky and despicable way for business owners to capitalize and make money! We should all be outraged!"

...as you may have got that part wrong. You simply don't need to measure a known known (eventually) that was all I was saying.

Still, according to what you may have understood as being implicitly contained: all depends on how (from what side of the fence) you see it. After spending a fortune and ages in research to finding some well working formula, your first thought will probably not be to make it public domain and in the same time hand it over to the concurrence, unless you are naive.

Don't be outraged! Better gather all the necessary info and knowledge and you'll be able to do it all by yourself and soon enough lay hand on ridiculously cheap nutrients.

Why do smart and ambitious people make money out of "processed stuff"? Because most people are too lazy to "process" it themselves and are afraid of going through the painful process of learning (to process). And when I say learning, I mean real LEARNING, not farting around and smart-aleking in forums during prepaid office-hours and sorting out the blah from the blah, adding some blah and still not exactly knowing what to believe, what is actually what and who is who.. LOL

Okay, this has turned into quite the hard-to-understand lesson, which I was trying to avoid. When you start throwing out words like Micro siemens and showing mathmatic formulas, it's not really helping me. I realize that it's difficult to break this all down in layman's terms, but I basically just wanted to know if I need an EC/PPM meter for indoor container gardening. If so, why do I need it? If not, will a regular pH meter come in handy? Do you have any recommendations for one that is easy to use?

I can't halpe you igrowindoors...

but I do have a question for the guys...
I bought an EC/TDS meter... does that mean it can read in moth EC AND TDS? And that's good...right?? When I start my journal, should I write BOTH down every time I measure? Would that be helpful or a waste of time?
**my brain hurts**
lol
~~Cheri~~

I'm sorry igrowindoors, I was trying to explain it in as simple terms as possible while still providing useful information. I threw out μ siemens to try and explain the difference between EC and TDS.(you did ask how they work)
In a nutshell, it will help you adjust your nutrients if they're too strong or too weak.

example: take an EC(or TDS) reading of your initial mix. if you find it is too strong, mix your next batch to a lower EC(or TDS) number. if it is too weak, mix to a higher number.Do you have to have an EC meter? no. Is it helpful? yes, if you use it that way.
pH, on the other hand, is much more important as too high or too low a pH will lock out certain elements. if you have good water and don't have to adjust pH much, it's not critically important, but until you've tested it enough to know, well basically you won't. That's why I recommend the test paper at first. its inexpensive and simple to use. if you find yourself needing to test frequently, then you'll want to buy a meter.


cheri Berry;
a lot of meters will show both EC and TDS, but you don't need to record both. one is simply the other multiplied by a constant (i.e. EC x SF = TDS, where SF=scale factor)
PS remember your brain hurting is a good thing, it means you're giving it a workout.

@grizzman: now that's helpful. thank you. I'll go out the simple route and get some test papers first. I grow in containers with soil so I think an EC meter is not necessarily needed for this method; it's more suitable for hydroponics and gauging chemical fertilizer amounts.