Data geeks unite!
So for DO probes, there are two primary types. Polarmetric and luminescent(LDO). The preferable type is luminescent. Polarmetric is touchy, sensitive to solution velocity, and drifts. But, it also the least expensive.
What I have is a Hatch LDO probe along with a Hach meter. Their stuff is very expensive although, by being patient, these can be had via Ebay. I ebay'ed a used LDO probe and simply purchased a new LDO "cap". From what I recall, I was able to get the probe for ~$100, the replacement cap ~$100, and the meter for ~$200. So, yeah, even used it is pricey. If you are willing to spend some sweat equity, industrial meters/probes can sometimes be had on the cheap.
A polarmetric Milwaukee DO probe + meter are available for under $200. There are downsides to the polarmetric method but may be perfectly suitable depending on how it's going to be used.
For on-line process, the newest generation of LDO require no calibration ($$$), Hach LDO® Model 2. But, money to burn?
For what I'm doing, the probe needs to stay stable for long periods of time while submersed. LDO is better for that. And, I can say that DO probes in general are a bit tricky to use/understand in practice.
That would be excellent. If we can get folk with various set-ups measuring the DO %, rates, plants in-situ / ex-situ, we'll have data that well exceeds what is currently available on the interwebs.
Understanding, measuring this is fairly difficult and expensive. It requires a certain amount of data geeky-ness to get sensible results. Right now, viewing the past experiments available from other sources, I feel their results may be a bit "misleading" as they avoid looking at things like saturation rate, etc. A comparison using an improved experimental methodology would be valuable.