Quote:
Originally Posted by Luches
There is no such thing as a "ppm test pen", at least to my knowledge. PPM of every element varies and hence cannot be measured (unlike EC) as a total concentration. PPM can only be calculated accurately from each element's molecular weight and content in a raw material or component. If you are looking for EC or TDS Meter (instrument), you should make your own online search specifically for your country, region and your own currency...
Sorry to be that blunt, Dear - but this is actually not the lazy people's hotline! 
I am willing to answer any decently formulated (and basically intelligible) question though, that can not be found or googled easily and in a minute. 
Thanks for the understanding. |
This was a VERY poor answer to the question.
To begin with EC, TDS, and PPM all measure the same thing. They measure EC. The major difference is how they report the reading. EC is EC not matter what meter you are using, whereas PPM/TDS will vary from meter to meter. There is a conversion factor involved with PPM/TDS. The 3 conversion factors are .5, .6 and .7. Mine uses a factor of .68. When a nute lists the PPM/TDS strength in their product is in important to note what factor they are using and adjust accordingly. I use GH Florenova nutes and GH's chart call for a factor of .5 my meter uses a factor of .68, so my reading will be off and I adjust according to how well the plants are doing. If I see leaf burn I will back off a little, I am growing celery in a DWC, and spinach in an E&F. i adjust the nutes to about 950-1000 PPM.
And yes they do make PPM/TDS pens I have one, it uses a factor of .5.