# TDS meter calibration



## grodude (Feb 17, 2015)

I understand that for PH meters there are ph 4.0 and 7.0 to calibrate the solution. I am looking at a TDS meter and would like to know what I need to keep it calibrated. I saw a brand that had 1000ppm and 342 ppm solution. I then wanted to see the General Hydroponics version as they are usually more affordable and found only a 1500ppm solution. Can anyone help me with this? Thanks


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## Dman1234 (Feb 17, 2015)

Theres all kinds, mine is 1383 ppm its just to verify your accuracy, having a hi and a low does seem beneficial though, like ph 7 and 4.


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## MR1 (Feb 18, 2015)

This is from Zem, you could give it a try. 





> My meter has written near the calibration screw "calibrated with NaCl" AKA salt. 1 gram of salt in 1 liter of water is 1000ppm. when I got it it was calibrated and i have a gold weight scale so i got 1 gram of salt in 1 liter distilled water and tested it, it was like 990 or so, but it was calibrated to 350ppm so i calibrated it to 1000 and it works great and i have a 1liter bottle of 1000ppm solution


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## zem (Feb 18, 2015)

:yeahthat: although there is the possibility of it being 10ppm+ or - but then again, any reading is not 100% accurate, and such accuracy is not needed imo. no one can precisely tell what exact ppm the plant wants in the first place. i tried this meter with bottled water with labeled ppm and get very close readings even at low ppm


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## Dman1234 (Feb 18, 2015)

Good info.


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## Hushpuppy (Feb 18, 2015)

All TDS meters read in EC which is electrical conductivity. But most of the American used meters are translated from EC to PPM. There is an algorithm (actually 3 different algorithms) that the meter has in its circuitry that changes the EC reading to PPM. Different meter brands use a different algorithm. It is important that you get the calibration fluid that matches the meter because of the 3 different calibrations for the meters that read in ppm. If you use the calibration fluid that is set for a different algorithm then your meter will not read right once calibrated with the wrong fluid.


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## grodude (Feb 18, 2015)

Hushpuppy said:


> All TDS meters read in EC which is electrical conductivity. But most of the American used meters are translated from EC to PPM. There is an algorithm (actually 3 different algorithms) that the meter has in its circuitry that changes the EC reading to PPM. Different meter brands use a different algorithm. It is important that you get the calibration fluid that matches the meter because of the 3 different calibrations for the meters that read in ppm. If you use the calibration fluid that is set for a different algorithm then your meter will not read right once calibrated with the wrong fluid.



Are you saying I should not use the salt trick and get the branded solution?


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## Dman1234 (Feb 18, 2015)

Hushpuppy said:


> All TDS meters read in EC which is electrical conductivity. But most of the American used meters are translated from EC to PPM. There is an algorithm (actually 3 different algorithms) that the meter has in its circuitry that changes the EC reading to PPM. Different meter brands use a different algorithm. It is important that you get the calibration fluid that matches the meter because of the 3 different calibrations for the meters that read in ppm. If you use the calibration fluid that is set for a different algorithm then your meter will not read right once calibrated with the wrong fluid.



Good info again.


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## MR1 (Feb 18, 2015)

A good average is .7  x ec= ppm.


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## Kraven (Feb 18, 2015)

This might be helpful


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## Hushpuppy (Feb 19, 2015)

I can't say don't use the salt trick or not because it totally depends on the algorithm used by your meter. The manual should tell you which it uses to calculate ppm. Just like the above chart shows, there are 3 different calculations used. One is with 500, the other is 700, and the other is 640. But if your pen is calibrated with the 500 and the salt sets up a ppm that is ffound with the 700 calculation algorithm then using the salt will make your pen read wrong. However, if the salt is found with the 500 algorithm and the meter uses the 500 as well, then you could use the salt. Its easier to just get the calibration solution that goes with that meter as you will not need much because TDS pens don't generally need to be re-calibrated very much iff at all.


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