Getting a Conditional Controller to regulate EC and pH working

Did you remove all electrical devices and probes from the liquid you’re trying to measure, as @dookaloosy suggested to do? Easiest testing setup is a glass of water beside the tank.

Also, I can’t find you mentioning it, but are you using an appropriate probe for the measurement range you’re calibrating to?

yes i have done all test in a pot of water,
the calibration values are ok,
but the measured water values are absolut wrong.
I have another ec meter from bluelab to check the values

Also, I can’t find you mentioning it, but are you using an appropriate probe for the measurement range you’re calibrating to?

the values with calibration solution ok, so the probe and sensor can read the range i want to use

Please provide a link to the exact EC probe you’re using.

It is the Gravity TDS meter
https://www.dfrobot.com/product-1662.html

do i need this one ?

Analog Electrical Conductivity Sensor /Meter V2 (K=1)

Just curious, what pH probe are you using?

I will say it’s a TDS probe so you’re kinda on your own, but the good news is that the underlying principles are the same, which means that calibration would likely take care of any offsets. From your observations, I am almost certain that you have some other electrical connection in your measurement fluid causing galvanic effects with your TDS probe (such as a pH probe, or a capacitive level sensor, a flow gauge with metallic parts, or even a ground wire dipping into the liquid). Any other electrical probes inserted in the system WILL affect the measurement, if you haven’t done the capacitor hack modification I showed. All that being said, @Roberto has been using the same hacked probe with good results and reported them here.

Did you remove all electrical devices and probes from the liquid you are measuring? Not just for the calibration? It is important to identify the source of the galvanic offset!

I have done all test in a separate box, no other parts inside.

The ph probe is atlas scientific ezo ph with isolation carrier board,
Now i have ordered a gravity ec meter set and hope to get better results.
The atlas ec kit is really expensive, so i will test the gravity ec set.

Did you type in “1413” and “12880” while calibrating? The calibrated values seem to show you typed in “0.1413” and “1.288”:
image

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Hello, after changing the tds to ec meter the values now ok.
I have calibrated the ec sensor and the measured ec value is the same
i can measure with my bluelab ec meter.
The next thing i have to do is isolate the sensor from the other sensors ( ph and temperatur) to get the real values. If the sensor is in a glass the alues correct. When i put it into the tank, values are crazy.
The value in a glas with nothing else is 1600.345
The same solution in the reservoir shows 83456.873
How can i isolate the ec sensor ?

I hae found this little board, but it is very expensive with postage


DFR0504 - Analoger Signalisolator, Gravity,

@dookaloosy mentioned a simple modification:

@bartonio I’m not convinced my capacitor hack is adequate, so I will recommend for now that you look at the Analog Signal Isolator boards from dfrobot (where you are buying your probes from). I am ordering a few to try.

My capacitor hack does indeed work at galvanically isolating the EC probe but it appears to insert impedance to the sensing circuit which affects the accuracy of the readings. Will report back shortly as I get more clarity.