# ppm 500 700 setting...



## linky (Nov 27, 2012)

I use house and gardens nutrients and was told to use the 700 scale setting on my meter (bluelab). I have a separate ec meter as well that I assume is set at 500... because when I set my bluelab to 500 I get the same readings as the other cheapy ppm meter, but ppm readings will change when I set it to 700. I am just curious though to why h&g's use 700 setting? Isn't ppm just ppm.. why would you have to use a different setting? Isn't it just reading how many parts per million in the water.. how/why would that change? Regardless of which setting I change to 500 or 700 EC still comes out to be the same though (if I remember correctly from the last time I checked).

thanks all


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## dbkick (Nov 27, 2012)

the ppm reading is a conversion of EC. 500 to 700 EC eh? EC is the only true reading, all others are based off EC using different conversion factors from brand to brand,


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## outlander1 (Nov 28, 2012)

You'll want to use the 500ppm setting.

*What's the difference?* The ppm 700 scale is based on measuring the KCl or potassium chloride content of a solution. The ppm 500 is based on measuring the NaCl or sodium chloride content of a solution and is also referred to as TDS - total dissolved solids. Individual nutrient ions have different electrical effects! The true ppm of a solution can only be determined by a chemical analysis. ppm cannot be accurately measured by a CF or EC meter. They are present on Bluelab products as a conversion guide only. The conversion is as follows;
2.4EC x 500 = 1200ppm (500 scale) or 1200ppm / 500 = 2.4EC
2.4EC x 700 = 1680ppm (700 scale) or 1680ppm / 700 = 2.4EC


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## insan3 (Nov 28, 2012)

Depends on the part of the world u are. .5 is mainly use in usa/canada while. .7 is use over the pond. Start learning EC as is universal.


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## linky (Nov 28, 2012)

Thanks for the info all, I was told house and gardens nutrients you are suppose to use the 700 scale.. so that is what i set my meter to. I have been using 1.2-1.7 ec in veg with meter set at 700.


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## BLOCKER (Nov 28, 2012)

i don't get, if my calibration solution , 1800ppm = 2.4ec, so i my ppm reading 1800, then i know that its 2.4ec so 900ppm 1.2, how can that go wrong?


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## Nick42 (Jul 21, 2018)

outlander1 said:


> You'll want to use the 500ppm setting.
> 
> *What's the difference?* The ppm 700 scale is based on measuring the KCl or potassium chloride content of a solution. The ppm 500 is based on measuring the NaCl or sodium chloride content of a solution and is also referred to as TDS - total dissolved solids. Individual nutrient ions have different electrical effects! The true ppm of a solution can only be determined by a chemical analysis. ppm cannot be accurately measured by a CF or EC meter. They are present on Bluelab products as a conversion guide only. The conversion is as follows;
> 2.4EC x 500 = 1200ppm (500 scale) or 1200ppm / 500 = 2.4EC
> 2.4EC x 700 = 1680ppm (700 scale) or 1680ppm / 700 = 2.4EC


This is backwards from Blue labs PDF download


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## Michael Huntherz (Jul 21, 2018)

All TDS meters are really EC meters that do a conversion. 


BLOCKER said:


> i don't get, if my calibration solution , 1800ppm = 2.4ec, so i my ppm reading 1800, then i know that its 2.4ec so 900ppm 1.2, how can that go wrong?


It won’t go wrong unless you’re comparing notes or working with someone else who is using a TDS meter on a different scale. EC is universal which is really helpful for communicating with others.


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## Michael Huntherz (Jul 21, 2018)

linky said:


> Thanks for the info all, I was told house and gardens nutrients you are suppose to use the 700 scale.. so that is what i set my meter to. I have been using 1.2-1.7 ec in veg with meter set at 700.


Using the 700 scale is not a law, you could convert all their numbers to 500 scale easily enough. But learning the EC route is a smarter path in the long run, regardless.


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## botanistprime (Jan 22, 2019)

outlander1 said:


> You'll want to use the 500ppm setting.
> 
> *What's the difference?* The ppm 700 scale is based on measuring the KCl or potassium chloride content of a solution. The ppm 500 is based on measuring the NaCl or sodium chloride content of a solution and is also referred to as TDS - total dissolved solids. Individual nutrient ions have different electrical effects! The true ppm of a solution can only be determined by a chemical analysis. ppm cannot be accurately measured by a CF or EC meter. They are present on Bluelab products as a conversion guide only. The conversion is as follows;
> 2.4EC x 500 = 1200ppm (500 scale) or 1200ppm / 500 = 2.4EC
> 2.4EC x 700 = 1680ppm (700 scale) or 1680ppm / 700 = 2.4EC


I don't think copying an pasting the same info regurgitated on every site is helpful. It shows you don't have the understanding required to answer. Anyone can Google homie. If you understand this then break it down. Otherwise this exact paragraph word for word can be read on countless sites.


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## BigHornBuds (Jan 22, 2019)

botanistprime said:


> I don't think copying an pasting the same info regurgitated on every site is helpful. It shows you don't have the understanding required to answer. Anyone can Google homie. If you understand this then break it down. Otherwise this exact paragraph word for word can be read on countless sites.


Reading comprehension is also helpful 
If you had that you would realize that your replying to a post over 6 years old .


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## Gquebed (Jan 23, 2019)

I was told when i bought my bluelab combo meter to make sure that i checked the scale of any ppm charts offered by nute manufacturers. Below is a pic of a GH ppm chart, but it doesnt have the scale listed on it. I suppose they use the 500 scale, but... can anyone confirm?


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## myke (Jan 23, 2019)

I have a cheap tds meter,Use tap water as a guide to check if its the same.My tap water is consistent year round.

I would very accurately mix 5ml per litre of your veg nutes.Use that reading as full strength or whatever your bottles say to mix.Keep to that setting and your set.


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## Keesje (Jan 26, 2019)

myke said:


> My tap water is consistent year round.


I doubt this.
It is almost impossible to achieve this by a watercompany.


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## primobozo (Jan 26, 2019)

Keesje said:


> I doubt this.
> It is almost impossible to achieve this by a watercompany.


My tap water is around 118, most of the time, but I have seen it as high as 130, and as low as 86. PH is around 8 through the fall and winter, and then drops off to around 7 in spring and summer. You can contact your water company and get a readout for your water, but it'll only tell you what is in it. It helps, but not a lot.


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## myke (Jan 26, 2019)

Keesje said:


> I doubt this.
> It is almost impossible to achieve this by a watercompany.


well close enough to consitent anyway.130-170 ppm .Only time it changes is when my local river turns to choclate milk from spring run off.


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## OldMedUser (Jan 26, 2019)

Print this out and have it handy for a reference.


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## Keesje (Jan 27, 2019)

What is the reason that all the brands do not switch to EC?

Also did not understand why most countries did not change to the metric system when they could.


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## botanistprime (Feb 1, 2019)

Keesje said:


> What is the reason that all the brands do not switch to EC?
> 
> Also did not understand why most countries did not change to the metric system when they could.


Only 3 countries use standard over metric...


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## Keesje (Feb 8, 2019)

botanistprime said:


> Only 3 countries use standard over metric...


You're right.
What I meant was 'why did the countries that use standard (didn't even know it was called this) to metric when they could?'
Metric is so much easier and logic.
Even Sheldon acknowledges it


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## thekiwipablo (Apr 22, 2020)

OldMedUser said:


> Print this out and have it handy for a reference.
> 
> View attachment 4271451


hey man can you tell me if you’d use the truncheon scale if running the bluelab combo meter with the probe? do all bluelabs run at ppm700 as the standard?


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