user47444: I have a water level sensor and a PH sensor connected to my nodemcu via an ADS1115 . When I insert only the PH sensor into the water then everything works fine. But when I insert the waterlevel sensor into the same container the PH sensor seems to shortcircuit and I get 5V no matter the actual PH level. Is there anything im missing or a way to prevent that from happening?

user30198: That water level sensor uses bare metal which is in contact with the water. The PH sensors are sensitive for that kind of voltage in the water, even if it would be 0V.
There are isolated PH sensor amplifier modules. On forums are often discussions whether to ground an aquarium or not for a PH sensor. With a isolated PH sensor, you avoid most of those problems.
There are also non-contact water level sensors. For example capacitive sensor or even sensors that can be attached on the outside. Some sensors use the water pressure, but I don't know if this one is isolated: https://www.sparkfun.com/products/10221

47444: <p>I have a <a href="https://www.amazon.de/Sharplace-Wasser-Sensor-Modul-Arduino-Rot/dp/B075VHRGND/ref=sr_1_1?ie=UTF8&amp;qid=1529326945&amp;sr=8-1&amp;keywords=water%20level%20sensor" rel="nofollow noreferrer">water level sensor</a> and a PH sensor connected to my nodemcu via an <a href="https://www.adafruit.com/product/1085" rel="nofollow noreferrer">ADS1115 </a>. When I insert only the PH sensor into the water then everything works fine. But when I insert the waterlevel sensor into the same container the PH sensor seems to shortcircuit and I get 5V no matter the actual PH level. Is there anything im missing or a way to prevent that from happening?</p>
 30198: <p>That water level sensor uses bare metal which is in contact with the water. The PH sensors are sensitive for that kind of voltage in the water, even if it would be 0V.</p>

<p>There are isolated PH sensor amplifier modules. On forums are often discussions whether to ground an aquarium or not for a PH sensor. With a isolated PH sensor, you avoid most of those problems.</p>

<p>There are also non-contact water level sensors. For example capacitive sensor or even sensors that can be attached on the outside. Some sensors use the water pressure, but I don't know if this one is isolated: <a href="https://www.sparkfun.com/products/10221" rel="noreferrer">https://www.sparkfun.com/products/10221</a></p>
