Does anyone Have a conversion table From 700 ppm to 500 ppm scale?

I can’t seem to find a conversion table that converts the 700 ppm scale to the 500 ppm scale. Can anyone help? @dbrn32 @Myfriendis410 @MeEasy

500 is on the left (Hanna), 700 is on the right (truncheon)


Thanks Man!

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But you would HAVE to know what scale your meter is using, correct ? My cheapo vivosun 3 in 1 does not say, nor could I find anything at all about it via google. I just this am ordered value series apera.

@pr No you can use the chart to determine your meters scale. Test your tap water and compare to the chart. Say your tap is 200ppm. If you switch to ec, if it says .4 then it’s a 500 scale meter. If it says something like .28 then it’s 700 scale.

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So I tested my tap water, my meter says 280 ppm. Confused how that tells me my scAle of my current meter.

Switch to EC and see what it reads. Should have a mode button that switches between ppm and EC

My current meter only ppm and ph modes. Have ordered the apera, value series, tds and ph meters. 2 separate meters.

The cheap TDS/ppm meters made for the US market are normally 500 scale.

Ive been trying not to ask you, but im getting the apera value tds20 meter. With that, being in ocean forest, and using gh maxi grow, what is it I need to know?? Scale gh uses? For some reason ive gotten myself totally confused again. Like my vivosun tds meter says my runoff this am was 980, but I don’t know what scale it is, if that makes any sense. @Hellraiser

You can use the tds meter to help you figure out when to start feeding, check runoff and when it gets under 1000 ppm, then start feeding with your GH nutes. The vivosun tds is on the 500 scale, I used to have one.

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Or say if my vivosun is 500 scale, and read 980 ppm, is it really a different # ??

I guess my main question is this. If the vivosun meter is 500 scale, and reads 1000 ppm, and if it weren’t 500, it was 700 scale, and read 1000 ppm, what’s the difference???

The difference is the solution tested (runoff or nute mix) would not be as strong or concentrated as you would think it is. If the vivosun was 700 scale and reading 1000 ppm on runoff, you might think you don’t need to feed yet, but in reality you would want to feed as it’s at 714 ppm using the 500 scale. The US uses 500 scale, Europe uses 700 scale, mostly. That’s why I went with an EC meter, no confusion, EC is the same worldwide.


Wish I would of known before ordering tds instead of ec. So the Apera tds20 is 500?

TDS is total dissolved solids which is read in ppm (parts per million) AND ec (electric conductivity). EC is universal. Think of EC like the temperature. Then you have different ways to read temperature. Celcius and Fahrenheit (700 scale and 500 scale). Some of the apera meters can switch between 500 and 700 scales.


No biggie, TDS is fine as long as you are aware of the different scales and know what scale your device is.

I believe the Apera can do the different scales but should come defaulted to 500 scale since they are a USA company.

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Good info and clarification from you and bobby digital. Thanks. Been driving me nuts. On the plus side, alls good in the tent. Will post in the am. Much more picturesque after being up for 12 hrs as opposed to just waking up. Thanks again to both of you.

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