n4alpaca
Active Member
I think that it would be feasible that if one had a good multimeter, it would be possible to tell the ppm and EC of a nutrient solution or even tap water after receiving the impedance (resistance) readings and using a little math. Starting with the electrodes exactly (or as exact as one might get the electrodes) one cm apart we stick the electrodes into solution very quickly and wait until we have a semi stable measurement (you can see a pattern in how the numbers increase) and then pull them out as to cause as little degradation of the electrodes as possible and to make an attempt at keeping net ion movement to a minimum (hopefully +/- 1 ohm accuracy). now we have an number in K ohm or ohm. Conductivity = 1 / R so divide one by the resistance. This will give us a measurement in Siemens/meter so... hopefully the number will be similar to the EC reading if you divide by 0.000001. Multiplying by 500 (conversion factor for NaCl calibration) should give a TDS type reading (hopefully). The deviation caused by the temp can maybe be figured out by replacing R with R(T)--- > R(T) = R1 [1+alpha(T-Tr)] where R1 is the resistance (ohm) at T or the temperature of the reservoir and Tr is a reference temp. which should be specified by alpha (oh yeah... everything has to be done in Celsius) I'm not sure yet. Unfortunately one should not yet do these calculations as we are missing the alpha. If this interests you please help me with this part. Alpha here is used to denote resistance change per deg c also it is said to be linear. So if you wanted to try to help this is kinda hard to do, but Measure the temp as exactly as you can and the measure the resistance as fast as you can and do it as many times as it entertains you. Generally 4-10 data points would be nice to have (one of which is at room temp). Alpha will be different for everyone. Unfortunately my Multimeter is crap and I haven't gotten around to getting a better one yet, so if someone finds this interesting again, please try it just keep in mind that this is very theoretical.
also just if anyone might wonder conversion to ohm from k ohm is k ohm*1000.
also just if anyone might wonder conversion to ohm from k ohm is k ohm*1000.