Calibration of PPM/ph meters, general hydro info

[cherrycherry]

Hey I just wanted to start a general thread regarding feeding your plants hydroponically. I know this may seem like a very basic question but it I'm new here and it's somewhere to start: Okay so I purchased a PPM meter and I want to feed my plants some nutrients at say 400 ppm. My tap comes out at around 400 ppm anyway so do I add nutrients to make it 800 ppm then feed to my plants?

Okay so if this is true here is a follow up question. Should I set my ppm meter to reflect the NPK (nutrient salts I AM ADDING, this would read 400ppm after I added) or the total of my hard water and nutients (reading 800ppm)

I guess I am confused because if this is what growers do whats the deal with calibrating your meter using the two different ppm calibration solutions that come with the meter. Does the meter eventually start reading false and needs to be calibrated? This is the impression I am under. Also do electronic PH meters need to be calibrated often or will they read true (right out of the box? after a couple grows?) When should I be calibrating my meters if at all?

 

[fatman7574]

The meter should be calibarted with know ppm calibration fluid and not adjusted from that point. Adding a 400 ppm solution to a 400 ppm solution soes not necessarilly give you a 800 ppm solution. As an example a nutrient solution may have 200 ppm of three different fertilzers added to it but the final nutrient fertilizer ppm will not necessarily be 600 ppm.
For an example, this is the Lucas method combination og 1 Part G Floramicro and 2 Parts Florabloom:
Nitrogen 167
Phosphorus 333
Potassium 397
Magnesium 100
Calcium 215
Sulfur 133
Iron 3.33
Manganese 1.67
Boron 1.67
Zinc 1.00
Copper .33
Molybdenum .03

Added up it contains what one would think would produce a reading of 1353 ppm. However it produces a reading of 1904 ppm. That is a difference of 71%

While the differences would not be near as great in your situation if it would still have an effect. A solution of 400 ppm with nutrients added to it to bring the ppm up to 800 ppm would contain a different amount of nutrients than desired. You would nearly always end up with a weaker nutrient solution than say making up a solution by adding twice as much to a measured anmount of RO water then diluting it with an equal amount of tap water. The second approach would be the safer way to mix your nutrients. Or just buy a single gallon of RO water and mix your nutrients and compare the different tds readings to the same mount added to a gallon of tap water.

 

[cherrycherry]

Hey thanks man I have to be honest I don't completly understand. To be honest I had just read the thread on a chart for PPM during the different growth stages. I have heard it is deadly for a plant to absorb water that is 1600 PPM or over is this true? Also I would like to pose a question for all you hydro gardeners out there: What is your basic routine for obtaining water and giving it to your plants. I also want to ask what is the average tap PPM people are experiencing and how many of you (Pro or not) use an RO filter!

I just checked my bathtub tap (what I use to water my plants) and its at 515 ppm! My sink right next to the bathtub is reading 505 ppm! This is also over the US EPA's max contaminant level. What should I do? What are you doing? Very curious!

 

[cherrycherry]

But ya fatman I do understand what you are saying about my meter and about how PPM is not linear. But say I add the same amount of nutes to a gallon of tap and a gallon of RO. The RO is presumably zero ppm? So I added the amount of nutrients until the meter hits (say Im trying to make an 800 PPM light veg solution). Then I add the SAME amount to the tap and take the reading to establish what I should be giving my plants? Yes this all makes sense! So the other dissolved salts from my tap are simply impurities or just non-benificial to the plant?

So lets say my second nute solution (in the tap water) reads 1300. I give my young vegging plants this water that reads 1300 PPM and it will not harm it? What about when Im in late veg and I want to give my plants 1600ppm solution of nutrients should my meter potentionally reads near or over 2000 ppm after it is added to the tap? Is this common or should I definatly not give my plants water that is at 2000 ppm ever?

 

[fatman7574]

Nearly always the bulk of the TDS in tap water is solubale calcium. This can be removed by heating the water and while the water is hot running the water through a foliter, such as several coffee filters. If the water is allowed to cool the calcium goes back into solution. You must filter it ut as a particulate (calciunm carbonate) while it is still hot. The reamnder is usually about 9o0 to 95% crabonates with magnesium, potassium, phosphorus and iron. They will seentially do nothing but act as buffers. They will not readily break doown into their original parts but yes they will cause a higher TDS/EC reading. With ions the readings are never linera as new compunds are always forminf tec and the EC is not the msmae. A TDS meter is really justa EC mter that give a read out in a ppm taht is a mathematical approximation derived from the EC reading it not a reading., therefore if the EC is not really accuratte the TDS is not either. A laboratory would actually go through a tr hree step or four step procedure to calculate TDS. Ie weigh container with water, remove filterable solids, then evaporate away the water and subtract the weight of the dry solids and the container and therefore be left with the weight of the Total Dissolved Solids. An TDS/EC meter is just a best guess method of approximation based on the ability of ionic salts to carry an electronic charge.

 

[cherrycherry]

Very interesting you seem to be very knowledgably fatman and I thank you very much for your input. So I now understand that TDS and EC are not exactly in themselves as they are read on an electric meter. What I still need clarification on is if I am trying to never excede a nutrient level of 1600ppm (I burnt my plants last grow which was my second grow ever using hydro) and 1600ppm is what I have heard plants burn at from some videos I downloaded... I am just wondering if this is true and given that fact I am using tap water should I expect my reading to be slightly higher OR should I keep them the same and I simply cant feed my plants as much bc my water too dirty!

 

[fatman7574]

Burn is caused by major nutrients not calcium. There are a huge number of people who grow with nutrients formulated for tomatoes that has calcium at a 500 to 600 ppm level. I myself do not adovocate high EC nutrients. I run a TDS of only about 500 to 600 with RO water as a base water. Meaning I would likely run likely about 1200 to 1400 if using a water starting with a TDS of 500 to 600 ppm. If I do not see signs of a phophorous deficiency I don't worry about my TDS but just add water daily as needed, add fertilizer to restore the EC every day and change out the nutrient reservoir once per 7 to 10 days. And keep the PH within an acceptable range depending on your system type.

 

[algy1943]

Hey I just wanted to start a general thread regarding feeding your plants hydroponically. I know this may seem like a very basic question but it I'm new here and it's somewhere to start: Okay so I purchased a PPM meter and I want to feed my plants some nutrients at say 400 ppm. My tap comes out at around 400 ppm anyway so do I add nutrients to make it 800 ppm then feed to my plants?

Okay so if this is true here is a follow up question. Should I set my ppm meter to reflect the NPK (nutrient salts I AM ADDING, this would read 400ppm after I added) or the total of my hard water and nutients (reading 800ppm)

I guess I am confused because if this is what growers do whats the deal with calibrating your meter using the two different ppm calibration solutions that come with the meter. Does the meter eventually start reading false and needs to be calibrated? This is the impression I am under. Also do electronic PH meters need to be calibrated often or will they read true (right out of the box? after a couple grows?) When should I be calibrating my meters if at all?

hi guys , I have been trying to calibrates my ppm meter, but I cannot find any 130ppm liquid, anyone know where I can locate some?

 

[budman111]

hi guys , I have been trying to calibrates my ppm meter, but I cannot find any 130ppm liquid, anyone know where I can locate some?

Best to use tap water to calibrate, mines rarely changes from 20ppm so i use this to calibrate but if you dont know your tap waters ppm to start with it a problem.

 

[superstoner1]

Best to use tap water to calibrate, mines rarely changes from 20ppm so i use this to calibrate but if you dont know your tap waters ppm to start with it a problem.

another bad advice post. you always use calibration fluid to calibrate. you have to use the one your meter is designed for, but i have never heard of 130ppm calibration fluid.

 

[budman111]

another bad advice post. you always use calibration fluid to calibrate. you have to use the one your meter is designed for, but i have never heard of 130ppm calibration fluid.

I dont understand? bad advice in what way? my tap water is always say 20ppm, give or take a few ppm so if my meter is 'drifting' i 'tune' it back and has never failed me yet...bountiful harvests with very little nute burn so long story short, im not the fool buying ppm fluid 'bling bling' with my boosters