I just used some cream cleaner as per the instructions, never bought their cleaning kit.

I only cleaned it 3 times for the whole of last year, I always rinse the probe under running water straight after I've finished my measurements though, keeps the salt deposits at bay.

Whether I should be cleaning it more/less I don't know. It's always performed well no matter what.

EC-meters are quite robust and don't need much care. The most important thing is to let the probe dry well, after rinsing with water but before closing with the protection cap if there is any.

One more question. After I place it in the solution it gives me a reading and then quits blinking. Should it remain blinking the whole time it's in the solution, or does it shut down after the initial reading. Oh by the way lucas you and ethno were right about my leaf spots on my toms. After misting with epsom salt solution they perked up and other leaves don't seem to be showing signs of mag deficiency.

Thanks again, Tod

I have a question while on the subject of Bluelab truncheons. Is the larger range of the commercial truncheon much advantage over the standard truncheon? It seems to me that the commercial model would be less precise particularly down in the range where water hardness is determined. What kinds of plants require an EC over 3.6? They are both the same price and I can only afford one. How do I decide which one to purchase?
Thanks, Ken

Don't know about the functionality details of the truncheon, trenhes. Someone who has got one should know. and be able to tell

@ hardclay7a, If I remember well they have only a precision of 0.2 mS/cm EC, which isn't exactly precise. They are good enough to make up nutrients for amateur purposes, but they do not permit actual monitoring, as daily changes may occur in a range of 0.05-0.1! Which these instruments can't obviously register or display. I never use nutrient concentrations over 2.5 mS/cm (EC).

trenches
the truncheon automatically shuts off x number of seconds after taking a reading. if you take it out of the rez, then re-submerge, it will display again.

Thanks grizzman, that's what I thought but wanted to make sure. My nutes were too weak so I feel good about the purchase.

Thanks, Tod

Thanks Lucas, I'll try to face my inner fear of calibration solutions and on/off switches by looking into other options before I buy.
Ken

You should absolutely do that Ken!
You are certainly not the only-one who has to overcome some fears, misconceptions and other indoctrination that come with education and concerns any member of any society LOL.

When I was a young man, my Yoga teacher was revealing me one priceless thing that saved me many times from failure. It's called transforming a weakness into a strength by simply accepting the challenge ;-)

Have a closer look at most experts and specialists, - in many cases they were actually terribly bad at what they eventually would know and do best!

Cheers,
Lucas

Thanks Lucas,
My local dealer has a Milwaukee TDS tester model t75 that calibrates with a 1382 ppm solution and reads from 0.0 - 1999 ppm(mg/L). If I am understanding what I have read correctly, TDS/PPM units of measure are misnomers as different minerals/elements resist/conduct electricity at different rates. Would this ppm/tds range be equivalent to 0.0 - 4.0 mS/cm (EC)? Would this give good accuracy in the ranges I should expect to be operating? Or should I look for something that reads directly in mS/cm (EC)? Do I have any of this correct?
Thanks again,
Ken

Yep Ken,
My recommendation clearly goes for an EC-meter without conversation to ppm, as the conversation is not helping anything with hydroponics, but was and is confusing many people - as everyone should have noticed by now.

But as long as YOU know and understand the conversation rate of the instrument (500 ppm for 1 mS/cm is actually more practical than any other) it is actually as good as any EC-meter that reads mS/cm (or microsimens) only.

Yesterday I had an EC/TDS meter in hand that is able to adjust to conversion rates in a certain range. This instrument allows you indeed to adjust to any "self made" nutrient or any other nutrients, IF ingredients and their conversion rate from ppm to EC is known. With this instrument you can (after setting the corresponding conversion rate of one specific nutrient concentrate) read the total of actual elemental ppm. Firstly I though: how nice... but then I thought: what difference does it make for me, as I have calculated ppm and EC of my final mix already and in advance.... ?!

This would be interesting though, if manufacturers would give the actual conversation rate (coefficient) of their specific products and thus people could adjust and calibrate their instruments in order to be able to read actual (elemental) ppm, or at least get a very close reading of them.

Don't get confused here with my narrating, but go for an EC-meter or if you can't get any, a 500 conversion rate that in fact has a less "odd" conversation coefficient when thinking back/converting back mS/cm.

I entirely agree with lucas_formulas. EC meter is the way to go.

TDS/ppm meters will always be making assumptions about the relative proportions of different ions. But even if these assumptions are accurate at the beginning of using a nutrient solution, as the plants absorb nutrients at different rates, those assumptions will quickly go out the window.

Besides, an EC meter most directly measures the most salient variable, which is not the mass per volume solid content, but the osmolarity of the solution (which affects the water activity). An EC reading is the best proxy for how many moles of ions are actually present in one liter of solution.

I would advise to leave TDS alone.

On the Bluelab Truncheon: I clean it with water and wipe it clean on my jeans to ensure there is no mineral build up. Seems to be working great. This is year 3 for that meter. I'm one happy customer, to say the least.

Bloody Newbie trying to keep a low profile, LOL
I just came from HM Digital's site - www.tdsmeter.com. Great read. Describes everything we've been discussing. Calibration options, non-linear conversion factors, temperature coefficients. I found it very enlightening, I no longer feel intimidated by complexity. As a matter of fact I'm hungry for more!
Ken

@ guenthmonster,

No "smart-assing" intended but I believe you are overestimating and actually misunderstanding the functionality of commonly used and discussed "TDS-meters" a bit. They are not actually able to detect any ppm or ion concenrtrations and certainly no proportions of different elemental specific ions. All they do is actually and only measuring electrical conductivity as any common "EC-meter" does. Eventually they use a fix coefficient, either 500, 700 or 640 and convert mS/cm to so calculated mathematical/theoretical "ppm". As mentioned on several occasions, these are conversion rates for converting electrical conductivity of NaCl and PCl to total ppm content of THESE components. Right, it's a fallacy to think that "TDS-meters" are capable to detect or measure ANY ppm of any nutrient solution other than those of the conversion rate from mS/cm to "ppm" they use.

@ Lucas

The EC meter actually measures the total ionic concentration off all salts in the solution. It's the ions that each salt (chemical) has that causes a flow of electricity - the EC meter measures ALL these combined to give you a total number.

So, they ARE able to detect ion concentrations in contravention of your statement.

A PPM meter works the same as an EC meter but uses a 'calculation' to convert to PPM.

I wonder if there is confusion because there is also a difference between TDS meters for hydroponics and professional industrial grade TDS meters. Hydro EC/PPM/TDS meters, like has been mentioned, don't measure TDS. I have always found this shifty and personally feel nothing but EC should be used when discussing nutrients. Industrial ones measure TDS. It's not based on EC as EC isn't accurate. Not all solids conduct electricity (EC stands for electrical conductivity, btw). They measure TDS by PPM based on all material despite ionization. They also cost a lot more than any hobbyist will ever wish to pay. Also, the EC conversions to PPM and TDS are averages that may or may not be accurate depending on what solid is most prevalent in the solution since not all solids equally conduct electricity. An article was recently written on this in Maximum Yield magazine.

Here's the important part: EC doesn't mean anything without cultural components. Cultural components include measuring nutrient right the first time and using it's EC value as a baseline. Then after a couple weeks, you ignore that value as some salts are converted to toxins that still exhibit similar EC values. That is the whole point of changing out solution every few weeks. You can no longer rely on EC/PPM/TDS meter readings as they don't discriminate between good and bad salts. And different plants cause different changes to the solution in different time frames. EC meters are tools for maintenance and that is it. They are great, as long as your expectations are realistic. They can create confusion if you think, "but my EC is 1.6, why am I experiencing deficiencies?" EC values are only as good as the gardener interpreting them.

I tend to think and express in a pragmatical way, without loosing "the facts". And what matters to me is what is truly applicable in any context.

@ mikey_2 An EC-meter measures electrical conductivity based on total ion concentration in water, that's right but it doesn't tell you the ion concentration, nor does it translate it in numbers. Form a EC reading you can't draw any conclusion unless the ingredients that give a certain ion concentration when dissolved in water, are all known.

Single components have a known conductivity in relation to ions and ppm they leave when dissolved in water. But different components as part of a nutrient have various and hence relative conductivity factors. Thus the EC-reading can't give you any information about ions or ppm present, neiher of single elemental, nor of total ppm. Only If all components and their parts are known, EC-reading in combination with this info can give you total or individual ppm content only.

@ joe.jr317, Does any unit, ranging from foot, over kilo to gallon have got any "meaning" without cultural components and connotation? They all haven't got any meaning unless we "made it up" and got used to them - and yet they all serve us pretty well. Even the metric system based on Earth's circumference has a solid geometric base (indeed) but does that mean anything practical in daily use, or does it help US people to adopt it? ;-)

With so called TDS-meters (and the fact that they use ppm as a unit) it's different. Here we deal with a clear discrepancy, when using this "unit" with a nutrient solution. Because here the use of this unit creates the illusion we deal with something precise and known when we don't. It doesn't only create the illusion of a known unit, but there are 2-3 conversion rates in use which is causing even more confusion. As I explained earlier TDS meters translate in either NaCl or PCl standard, and thus have strictly NO correlation with the ions or ppm present in any common nutrient solution. To be even more clear: when using any of these so called TDS-meters of any conversion rate with a nutrient solution, it gives a FALSE ppm reading. And that's the important point and difference here, I believe.

So my conclusion simply is to stick with EC, as at least it gives us a unique and true unit to get used to "culturally" and allows us to reliably use and work with. Furthermore, from EC alone we can draw conclusion of actual PPM content in a nutrient solution, as soon as we know the ingredients and their part.

PS: The fact that a nutrient solution changes with plant's uptake and that measuring it's concentration gets more and more unreliable because of the + and -ions changing, doesn't affect the choice between a EC or TDS-meter or the respective preferability of a unit. Both instruments are equally concerned by this effect.

And as we are at it, with a more advanced monitoring of both, PH and EC changes we can indeed draw conclusions to improve concentration and composition of a nutrient with the goal of keeping the balance as long as possible instead of changing the nutrients "frequently". Hence If in the right hands, a EC-meter (in combination with a PH-meter) becomes more than just a maintenance tool. ;-)

Cheers and we are in peace - always,
Lucas

@ lucas_formulas,

That's a good point, since TDS meters do directly measure the same thing with an extra step of conversion, they could easily be used in the same capacity as an EC meter. As long as the user understands that the TDS reported is a reflection of the EC measured by the device then there is no problem with using one. Thank you for the clarification.

@ mikey_2,

While EC meters do in a way measure concentration. It is not the mass per volume concentration of solutes, but rather the number of charge carriers per volume in the solution. The EC depends approximately linearly on the number of charge carriers, and thereby measures the number of ions per volume in a solution. The problem is that since different ions have different masses, and different solutions will have differing concentrations of ions, it is unreliable to take the overall charge carrier density and convert that into a mass of solute per volume solution concentration (which value a PPM measurement would reflect).

@guenthmonster,

Right and that was my point earlier, TDS-meters are fine as long as you got the plot. But the users have to truly understand that the "extra step" of conversion has initially a different purpose, the one of measuring actual concentration of either NaCl solutions or PCl (as in potassium chloride) solution. Unfortunately this isn't what people who bought/own such instrument want to hear, - they prefer believing they're measuring some actual ppm of their nutrients ;-) The extra conversion step is responsible for the fallacy at the end...

And what you explained to mikey_2 is true, but as explained earlier, if you know the exact components and proportions of a nutrient solution, you actually can deduce ppm from EC-readings. In fact, if you knew the exact composition and proportion and own a TDS-meter with adjustable conversion rate, you could in fact read actual ppm of a specific nutrient solution. Not 100% accurately, but the reading of elemental ppm would be very close in (let's say) a range between 1.5 and 2.0 mS/cm. But again, what would be the purpose if you can deduce it mathematically anyway or as well.... ;-)

@ lucas_formulas,

If you do know the exact components and proportions of a nutrient solution you could deduce PPM from and EC reading, but the proportions of nutrients begins to change as soon as you let the nutrients come into contact with the plants' roots. It just gets farther and farther in from what you had originally in terms of proportions of nutrients. That's what I meant by saying that the conversion rate quickly goes out the window, because even if you know an exact conversion rate when you start using a nutrient solution, it quickly changes (hence the need to change nutrient solutions every so often).

Yes that's correct, you could even say that a nutrient solution isn't exactly a stable solution. There are always chemical processes going on "in nature" or in such kind of "solutions" even without plants feeding on them but literally, already when exposed to the atmosphere ;-)

But then again, how quickly and how much the composition actually changes, depends on the volume of nutrient solution versus amount and size of plants. But yes, however, you can't deduce the part of each and every element any longer and the total elemental ppm can't be read any longer either. I wasn't saying that anyway, or was I? The only point here is, that you could make up a nutrient solutions concentration and say how much ppm it will (initially) have (single elemental parts and total). Something, how strange it may ever sound and actually be, you CAN'T do with a so called and commonly used TDS-meter, that displays "ppm" with a fixed mS/cm to ppm conversion rate.

The actual need of changing the nutrient solution is a very relative and quite controversial matter as well. To know more about what I said about advanced monitoring of PH and EC earlier, and how both become more than just a "gauge", you may read through this article:

Here is a link that might be useful: Control Track