Interference between pH and DO sensor

Other Hardware Sensors
1

So I've been trying to setup the pH Meter Pro from Dfrobot aswell as their Dissolved Oxygen Meter.

After a lot of tinkering around with it I was finally able to find the issue that's causing the two sensors not to work together in the same container.

The DO sensor causes a voltage between water and arduino ground of 0.6V as soon as I insert the sensor into the water. This makes it impossible to get any useful readings from the pH sensor. When I remove the DO sensor again the voltage slowly drops back to 0 and the pH readings recover.

Is this intended behavior of the DO sensor? And is there a way I can get both sensors to work in the same container?

2

Sounds like a problem with the DO sensor probe. The connections to the probe are properly grounded, according to the amplifier/interface schematic.

Don't use the two probes in the same water sample, or separate them by a grounded plate.

3

So I tried putting a steel mesh, connected to ground, into the water. This dropped the voltage to about 0.25 (slightly increasing over time). The DO sensor didn't seem to be influenced by that but the voltage is still too high for the pH sensor to give me any accurate readings.

4

How, exactly, are you measuring the "solution voltage" with respect to Arduino ground? What are the various probe positions?

It is really hard to imagine that a grounded conductive mesh won't fix the problem.

5

That grounded mesh itself is likely to interfere with the sensors... as both are trying to produce an electrical potential.

Having the sensors on electrically separate circuits is the most reliable way of not having interference, not straightforward to do.