I understand that the pH probe and other probes can get disturbed from each other, and output inaccurate and off readings, when they're in the water.
Does anybody have expirience with this and how to solve it if it is a big problem.
Best Regards Victor.
Best solution: put the pH probe on a fully isolated circuit. So isolated power supply & isolated communication.
I just finished designing a board that should be able to do pH and EC... two isolated circuits, two MCUs & two optocouplers to get the data out... hope it's finally going to work this time around. Not easy or straightforward to do.
So an arduino for each? and is it only the pH probe or is it altso other probes?
And why do you use the optocoupler when you have two MCU, an powersupplys?
@wvmarle and could u make alle of the sensors work on one arduino using the optocoupler on everyone?
sry for all of the questions
That optocoupler is to totally electrically isolate the MCU that reads the sensor from the outside world. No electric connections whatsoever.
You can accomplish the same by running the Arduino off batteries, and make sure the only electrical connection (including signal wires via other peripherals) to the water is the pH probe. Or mains powered and have absolutely nothing else to do with electricity touch the body of water you're measuring.
Okay, so even the Ground from a heater fx could affect it? Og they’re plugged in to the same extension cord?
Is it the same with temperature and ec?
And Can u send power thru the optocoupler?
victorlh:
Okay, so even the Ground from a heater fx could affect it? Og they’re plugged in to the same extension cord?
Yes. Depends on how the heater is constructed.
Is it the same with temperature and ec?
EC is less sensitive (at least my sensor is not too sensitive, but it will still be affected). EC and pH do affect one another.
victorlh:
And Can u send power thru the optocoupler?
No. Just data.
Alwrigt, thank you!
EC is what? Electrical conductivity?
pH and conductivity can be measured successfully in water by keeping everything separate.
Individual pH and conductivity meters, portable, battery powered will work without interference provided they are not connected through common grounds.
A pH probe with a FET amplifier will run on a battery for a long time. Conductivity ideally needs an AC source but for short periods, DC will do. A couple of stainless steel probes on a multimeter in resistance mode will work.
Water quality monitoring equipment routinely has anything up to six probes in a single "head".
A lot more difficult if you are working with a common power supply.
Yes, EC is electric conductivity, a measure for the amount of fertiliser (mineral salts) in the solution.
If your period is shorter than about 1 ms, DC should indeed give you a reliable reading. After that, the conductivity starts to drop rapidly as the ions move around and electrolyses starts.
Commercial instruments more often than not use graphite electrodes - stainless steel, especially grades like 304 are pretty durable.
For a DIY setup, I wonder if there is any mileage in trying something like pencil leads? A softish grade - B - from something like a carpenters' pencil that has large diameter (actually oval or rectangular) leads might work.
Commercial probes have several concentric graphite electrodes like a stack of Polo mints, embedded in in insulating material like Tufnol.
Electric motor graphite brushes might be another source.