Author Topic: Recalibrated NovaLynx rain gauge  (Read 986 times)

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Offline miraculon

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Recalibrated NovaLynx rain gauge
« on: November 06, 2015, 09:42:39 AM »
I recalibrated my NovaLynx rain gauge earlier this week. My previous attempt used a 1/16 inch orifice, this time I used a #72 gas orifice which is .0250 inch according to online resources. The drain times for this smaller orifice were significantly longer than the larger one. It was pretty much an all day project, but I think that it was worth the effort. Neighbors were asking what I was doing. There go those strange looks again...

Here are the new results from part of my CoCoRaHS comment entry for today.
CoCoRaHS=0.22"; Roving 4"=0.23" (set out again for this rain event). Davis VP2=0.20" NovaLynx=0.25" (re-calibrated on 11/3 using low-flow orifice)

This is much improved from the previous results. Here is a post in the "VP2 Rain Gauge way off" thread with a very similar rain amount all around. The difference is substantial.

My readings prior to making adjustments were 1.25 inches against a 1.19 inch calibration target for 946mL (per NovaLynx). This target assumes a 1/32 inch orifice.

After a couple of stop screw adjustments, I settled out at 1.19 inches, which is right on target. Today's actual measurements seem to confirm the improvement. (although a single data point is fraught with peril, it is encouraging).

Here are some photos of the setup I used to calibrate the gauge. I added a phone connector block to the input of the counter to match the "Davis standard" rain gauge connections. Here is the rain gauge contact signal brought out to the counter connection.

Here is the low-flow orifice in a PVC "funnel" that I made out of a reducer and cap. The orifice is mounted in the bottom of the cap, kind of "self-tapped" into the PVC. It doesn't leak.

I set up the counter on a folding ladder. The counter has a fairly dim LED and was really hard to see in the bright sunlight. I made kind of a light shield around it out of a little step-stool and knee pad. I would recommend an LCD counter.

Here is a little closer view showing the counter and the beaker used to pour the 946mL into the PVC funnel/orifice.

And finally, here is a close up of the counter. It had two things going for it. It was cheap and counted properly. Aside from being almost impossible to see outdoors, it was OK.

Greg H.

Blitzortung Stations #706 and #1682
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