TDS meter question...

R3dima

R3dima

Active Member
I just purchased a TDS-3 meter (HM Digital). I was curious is to how to get a breakdown on using the meter with my nutes, and if there is a conversion ratio that works with each specific model? or is it just the same.

Cause since I am having the yellowing issue with my plants and I am trying to address that with the deficiencies and Ph levels. But I want to get some knowledge on how to understand PPM and using my TDS meter. If anyone has some good links or some info I would greatly appreciate it!
Thanks
 
R3dima

R3dima

Active Member
endofwed said:
First off, have you calibrated your meter yet?


Click to expand...
The company said it was calibrated out of the factory with NaCI 342 ppm solution.
The other thing I was a little puzzled by is that my Aquasana filter read out 129ppm and the regular tap water read out 121ppm... I am confused...sounds like some trace minerals have been added and could be whats causing the deficiencies on my plants that are yellowing and seem to have a iron and zinc deficiency. I am thinking that they are using just a carbon filter with a softener. I am going to contact the company either tomorrow or this week and just get an RO unit under the counter, this way my nutes will be at a proper ppm...

If what I am saying sounds off please let me know...also I saw that chart, and I don't know what to read off it since my unit just says HM digital...
Thanks look forward for more info! :mrgreen:
 
endofwed

endofwed

Active Member
Sorry, I misread your first post and I thought it said you bought a hanna ppm meter, so i posted that since it could of been of some help. As for your HM meter, a lot of companies claim to be precalibrated but I think a lot of users will agree you will have to calibrate it yourself with solution to get a correct reading.

Im not too sure about the zinc deficiency. It would help a lot if you posted a description of your set up (lights, res gallons, ph..etc) along with how much nutes your adding and someone might be able to help you
 
patlpp

patlpp

New Member
click on: http://www.tdsmeter.com/products/tds3.html

Note in SPECS it says .5 conversion, therefore your meter converts the actual EC value to PPM by a factor of .5. Look on the chart you will see under HANNA in the first row ".5".

EXAMPLE: Look at the chart and find EC = 2 ms/cm (.002 siemens) which equates to 2000 uS/cm (2 ms/cm times 1000 because PPM is parts per MILLION) Than you take this 2000 us/cm number and multiply by .5 (your meter conversion factor) which equals 1000, that is the PPM value.
If you have a meter with .7 conversion, you just multiply the EC by .7 instead of .5 in the example, 2000 * .7 = 1400 ppm

Beware of feed charts that state a PPM value but fail to disclose the conversion factor or the corresponding EC value. I usually can tell what factor they use by looking at the PPM values in heavy bloom. If they go into the 1300 or on PPM value, most likely they convert @.7. A normal EC for bloom is ~ 1.8 - 2.4 EC

To convert from PPM to EC, take the PPM and divide by the conversion factor: 1000/.5 = 2000 us/cm or 2 ms/cm
 
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