Dr Who is right! ... Rx Green Technologies Report

twentyeight.threefive

Well-Known Member
correct. so a tds meter is not the same as an EC meter. thanks. a siemen and parts per million aren't the same either.

for further arguments: call these people and argue with them. this is just one source that says the same thing.
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ref: 06 Oct 2020 article
BTW I’m not arguing with you. I’m pointing out that you are wrong and I’m explaining to you why.
 

PJ Diaz

Well-Known Member
maybe i'm reading that paragraph wrong then. an ec meter measures electrical conductivity, a tds meter is only an estimate of electrical conductivity.

is that the same? i don't think so. if you think those are the same, that's fine with me
It's saying that the TDS meter also measures electrical conductivity, and then uses a conversion factor from that to estimate TDS.
 

twentyeight.threefive

Well-Known Member
maybe i'm reading that paragraph wrong then. an ec meter measures electrical conductivity, a tds meter is only an estimate of electrical conductivity.

is that the same? i don't think so. if you think those are the same, that's fine with me
No you’re reading it wrong. A EC meter measures and displays EC.

A TDS meter reads EC and displays ppm calculated from the EC reading times a scale. If it’s a 500 ppm scale TDS meter and the pen reads 1 EC then the display shows 500 ppm.
 

rkymtnman

Well-Known Member
It's saying that the TDS meter also measures electrical conductivity, and then uses a conversion factor from that to estimate TDS.
see post 204. so you think an estimate is the same thing as a measuremetn too? that's cool too.
 

PJ Diaz

Well-Known Member
If you see two little metal probes coming out of your ppm meter, it's measuring conductivity. It's basically a tiny preset resistance meter. Nothing fancy. It sends an electrical DC impulse out, and measures the resistance between the probes.
 

Billy the Mountain

Well-Known Member
sorry but that's not correct from what i've found

So, what is the difference between conductivity and TDS meters?
In pure scientific terms, conductivity tells you how well electricity is passing through a substance. On the other hand, TDS indicates the amount of dissolved solids within a liquid, accounting for both conductible and non-conductible particles.
In practice, when measuring conductivity and TDS both conductivity meters and TDS meters pass electricity through a liquid. In fact, conductivity meters are used to estimate the TDS in a substance.
How is this done? Simply, TDS meters measure conductivity, then apply a conversion factor. Even if your meter is a TDS-only meter and does not display conductivity it still uses electrical conductivity with a conversion factor to calculate the TDS results.
Why? Well, for a true TDS measurement you have to evaporate all the moisture from your sample, then weigh the solid residue. While this is the most accurate method, in practice it is often impractical.
In summary, there is a correlation between conductivity and TDS. They are not the same. TDS meters that use conductivity to generate measurements only estimate TDS


if they measure in 2 different units (siemens and parts per million) , they can't be the same thing. one is an estimation of the other.
I don't now where you read that a tds meter measures anything but conductivity, please share.
They both measure conductivity, and only conductivity.
The ONLY difference is the displayed value to approximate the ppm of a reference salt; in the case of TDS, 500ppm NaCl = 1.0 EC
 

rkymtnman

Well-Known Member
I don't now where you read that a tds meter measures anything but conductivity, please share.
They both measure conductivity, and only conductivity.
The ONLY difference is the displayed value to approximate the ppm of a reference salt; in the case of TDS, 500ppm NaCl = 1.0 EC
maybe i'm being too strict then with my definition of not being the same thing?

i think meter 1 that measures ec directly and displays that in mS is not the same thing as meter 2 that measures ec and then estimates a value of parts per million via 3 different conversion factors (0.5 , 0.7 and 0.64) and displays ppms.

anyway, that's my last post on this subject. if meter 2 converts and approximates, then it can't be the same thing as meter 1 that does neither. nobody will convince me otherwise.
 

Billy the Mountain

Well-Known Member
maybe i'm being too strict then with my definition of not being the same thing?

i think meter 1 that measures ec directly and displays that in mS is not the same thing as meter 2 that measures ec and then estimates a value of parts per million via 3 different conversion factors (0.5 , 0.7 and 0.64) and displays ppms.

anyway, that's my last post on this subject. if meter 2 converts and approximates, then it can't be the same thing as meter 1 that does neither. nobody will convince me otherwise.
Focus on the aspect that both meter1 and meter2 measure the exact same thing: conductivity.
The only difference is how they display that measured conductivity
 

twentyeight.threefive

Well-Known Member
maybe i'm being too strict then with my definition of not being the same thing?

i think meter 1 that measures ec directly and displays that in mS is not the same thing as meter 2 that measures ec and then estimates a value of parts per million via 3 different conversion factors (0.5 , 0.7 and 0.64) and displays ppms.

anyway, that's my last post on this subject. if meter 2 converts and approximates, then it can't be the same thing as meter 1 that does neither. nobody will convince me otherwise.
Wait. Wait about my meter that displays EC AND ppm? It’s not the same meter?

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Billy the Mountain

Well-Known Member
An estimate is pretty much a guess so in other words they guess the ppm from the EC
And a wild guess at that, unless your measuring table salt with a TDS meter

The displayed ppm value is only valid for the salt for which it's calibrated and nothing to do with the elemental ppm of a nutrient solution with various salts present.

For example, my current hot pepper feed of Maxi Gro/Bloom is 2.0 EC but the total elemental ppm is 663, a TDS meter would display 1000ppm
 
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