When Electronics Meet Chemistry: A Conductivity Sensor For Liquid Solutions

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@lezbriddon 7 ай бұрын

you have standing dc potential across probes. this will oxidize the probes. it will deposit chemical metals in the liquid making a metal poison cocktail. sensing current should be ac not dc. one probe could be sinewave from opamp oscillator, other probe to high impedance input opamp feeding notch filter detector

@eleneasy 7 ай бұрын

The current involved is very low and the probe is immersed in the solution for just a few seconds, so the oxidation process is very limited. In addition, we are talking about testing solutions that are already poisonous. Nobody would ever think of drinking those liquids. We are talking about high school chemistry. Also, using alternate current would not change much from that perspective. It would only cause oxidation on both wires instead of one, don't you think?

@lezbriddon 7 ай бұрын

@@eleneasy I think AC would cause less metal deposits, which is why manufacturers invented chipsets just for this. admittedly if I was going to measure the level of water for humans, i'd go with magnets and reed switches or a float/level/magnetic hall sensor. Your diagram works, but it does have the negatives as listed. I built one very very similar (ua741 based) when I was 12, so about 1978.....

@eleneasy 7 ай бұрын

@@lezbriddon I agree, there are negatives. But the device is just for didactics purposes and will never be so intensely used to to cause any sensible metal deposits. I had to build the device in a hurry, because my wife needed it almost immediately. Moreover, she needed a number of them, not just one, so I decided to go cheap and build one with minimalistic characteristics. And considering also that she was going to use it to make her students distinguish between ionic and covalent solutions, where only the ionic solutions would have allowed current to flow, and where those solutions where already made with a base of various metals, I didn't worry too much.