EC value fluctuation

Hi currently, I have this issue with the EC value as it keeps fluctuating. As you can see from the graph, the peak value is ~3700 uS/cm and the bottom value is ~1700uS/cm. The actual value is ~1600 when I measure with an EC meter so i dont know why it overshoot heavily like that.
The sensor I used is an analog sensor (Seed Studio ModBus EC Sensor) , I used a voltmeter to measure the output and it is stable at 0.155V for a good period of time i.e I did not see any oscillation
Any suggestion for this behaviour ?

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Have you tested removing all other devices from the water being measured?

I tried for 5min, took out the pH and temp sensor but the fluctuation is still there.

And those are the only things in the water? No pumps or other electrical devices?

yes i removed the pump as well but it is still fluctuating. I also try to turn OFF the power supply but the reading is still fluctuating. I believe there is sth wrong with the sensor? May be do another calibration?

Does it have the same behavior if you move the probe into a glass of water?

Hi Kyle, I decicded to wait for one day and see what happen. When I check the sensor, the reading actually stabilize after ~20hours but in wrong value (value = ~2300 but actual measure = ~ 1600). The odd thing is that when I take the sensor out t fresh water, the reading oscilate again

You can see the oscillation happened when I put the sensor in water but it stopped when I put the sensor back in the reservoir lol.

I think the probe might have issue but not sure

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You would probably have better luck contacting the manufacturer for support.

Hi Kyle, after some debugging, turn out the GND connection between the EC sensor and the ADS1115 module was loose, so they did not share the same GND, which explains the fluctuation. I reconnected it and the sensor reads perfectly now ^^

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