Leo,
It's about "sinking" and "sourcing", and yes, it is a bit complicated, but I am not talking about sink holes here
The well at our old shop was 284 feet deep and in the Marshall Aquifer. The water coming out of that had DO at just under 2ppm, so ground water can have some DO, just not huge amounts.
The first DO meter I got was an Extech, and it measures both DO and %O2 in air. Most self calibrate in air. It was under 500.00
The unit going on my RAS in the "Master" control is made by Mettler Toledo. It is accurate in the low ppb (like 3 parts per billion) range, and will measure up to 50ppm. The sensors are rugged enough to withstand the higher pressures of supersaturating DO if I side stream Pure O2 thru a turbine pump. Although, I would place them right at the end when the water gets to the expansion chamber. Not wanting to go broke buying multiple meters, I am trying to find a remote I/O module on Modbus protocol that can handle +/- 500 nano volts. I have one at +/- 250 nano volts, but not sure how the meter converts volts in to DO. If my hunch is correct, it should work, if not, the inputs are isolated and have over voltage protection. Worst thing that could happen is wasting some time. I can't imagine hitting 50ppm (same as 50mg/l). This process requires a very thorough gas stripping of the water before injecting O2 at the turbine pump.
Interesting subject! Thanks!
