Electrical – Omron E3JK R4M1

These problems are hard to diagnose. The first thing I would do is swap the level and pressure ADC inputs to make sure that there isn't some sort of software issue. Even if you've looked at the code a thousand times I would do this.

The impedance of your sensor is pretty high to feed directly to the ADC input. I think you should add a unity gain, non-inverting buffer between the sensor and the ADC input.

Bypass capacitors may be needed. There's not enough information to tell where they should be added or what their values should be. I would be sure to bypass the 5V supply for the sensor. You could add a small capacitor to the output of the sensor as well, assuming that the pressure is not changing rapidly.

You could also try slowing the ADC clock rate to give the sample-and-hold more time to charge. Sometimes putting the processor to sleep during a conversion can reduce noise as well.

Thanks for the responses to my question. I'm answering my own question because I was able to do some further research into this specific unit. Instead of getting limited answers through the vendor's tech support, I eventually found Eaton, the company that produces this item, and spoke to their extremely helpful sensor tech support person.

So the basic answer is yes, powered separately, the unit can be used with an Arduino. I should've clarified better that I was mainly concerned about using an Arduino with the unit's outputs. He confirmed that the unit's outputs are isolated from the power supply and can work with either AC or DC, so no conversion to DC is necessary. The outputs function as a switch contact whose state the Arduino could read directly. That said, tech support did still recommend the mechanical relay version as another user pointed out. Despite isolation on the outputs, there could be some current leakage with an SSR, whereas there shouldn't be any with the mechanical relay version, and my application is not a super-high-processing environment where a mechanical version would soon fail from wear and tear on the physical contacts (using the example he gave, not a UPS shipping facility where they would need a much longer-lasting SSR-version sensor to count tens of thousands of packages a shift).