How many PAR sensors do you have?

[djwain]

We are getting a new buoy. We had a PAR sensor in air and one at 2 m deep on the old buoy, and we are debating getting a second underwater one, but with the mounting arm and wiper it is another 4k, plus making the buoy more awkward for deployment with two arms. Tell me about your PAR sensor setup and if you are happy with it, plus how often you actually use the data from it!

[trexmiller]

If I ever have a PAR sensor on a buoy it is underwater at 1 m depth and I have used it (Licor) for estimating primary productivity (with DO). I did not have a wiper on it, but we cleaned it occasionally, probably not enough. I would like to regularly have them on all buoys in air and underwater, but time has not allowed it yet.

I have 3D printed adapters for Zebratech wipers to allow them to hold multiple sensors (fluorometers and PAR).

We have made PAR sensors with a color sensor that has a clear channel that reads between 400 and 700 nm. Epoxy it in PVC with an acrylic disk over the sensor for cosine correction. We are far from the first to do this... https://www.preprints.org/manuscript/202504.1750 . There are other examples of people doing it, just can't find right now. We compared it to a Licor underwater sensor and it was spot on.

[trexmiller]

Here's a better example of a DIY PAR sensor, similar to what we made.

https://www.scirp.org/journal/paperinfo ... erid=88576

[trexmiller]

Also, you shouldn't need anymore than two PAR sensors to establish the vertical extinction coefficient (K)

K = 2.3 (log I, h-log I (h+1))

l, h and I are light intensity at depths h meters and (h+1) meters