I have tried most of the ways mentioned elsewhere here to calibrate tipping buckets: comparison, Novalynx calibrator, burettes, syringes, etc. and have written about some of them
A while back I looked at my pile of tech and set up a little demo using a peristaltic chemical feed pump and plastic calibration column to deliver a steady known rate to a tipper. I think I posted about that, too.
Lately, out in the Think Tank, I have thought of ways to leverage that and some other tech and a little programming to see what I can do to automate the process and get better results.
Here is what I have come up with.
The Stenner pump and 100 ml calibration column.
A RUG9 controller (this could be done with any suitable controller, I think)
A relay output to control the pump
A digital input to count tips
Suitable programming.
So far, the plan is to have the pump controlled by the controller, on and off, and have each tip logged to an array or table, along with the duration since the last tip.
I think I will also program it to shut off the pump immediately after the last tip that would empty the column. This avoids the Novalynx problem of "untipped" water in the last bucket.
For instance, for the 100 ml column, a and a Davis tipping bucket requiring 5.44 ml per tip I would shut off the pump after the 18th tip, leaving a theoretical 0.38 ml in the column. Maybe I better start by shutting off after the 16th tip.
Knowing the initial position of the tipper ("left down" or "right down", say) and logging each tip and interval to the table means that I should be able to import the data to Excel, and separate out "left" tips from "right" tips, getting a better idea of which side needs adjusting and by how much.
Also, the Stenner pump has a 20:1 turn down, to make testing at other rain rates easy.
After a few test runs, a bench test on a VP2 with one dirty bucket and probably slightly off level shows that the pump at hand, with a #1 tube (3GPD), wide open produces about a 1"/hour rate. (100 ml, 19 tips, 5.26 ml/tip, 10.95 minutes). I think I have one #2 tube around here that should produce about a 3" per hour rate.
Time to start a little programming.
