Author Topic: WS-2902A Rain Gauge Calibration  (Read 607 times)

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Offline Buford T. Justice

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WS-2902A Rain Gauge Calibration
« on: November 03, 2018, 02:43:46 PM »
I have been lucky enough to have a few rain storms come through my location.  I own an official NWS rain gauge and it is very near where I have the WS-2902A sensors installed.  This allows me to tell how well the WS-2902A is measuring rain.

By default, it over-reports with the default calibration setting of 100.  I sat it down to 90 and waited for the next couple of rain storms.  This got it real close, but it was still slightly over.  Right now, I have it at 87 which seems to be the magic number at the moment.  Soon it will be snow so I will not know until next year when the rain returns.

On the calibration of the other sensors, I think these are actually perfectly fine.  I see no need to change the temperature or humidity calibrations.  The solar sensors are fine as well at their defaults.

You don't need to calibrate the barometer.  You just set it like you do with the clock via the SET button.  Once you have your MSL barometric pressure figured out, the WS-2902A really works well and agrees with nearby airports.  This has become my favorite weather station I have ever owned.

Offline tony

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Re: WS-2902A Rain Gauge Calibration
« Reply #1 on: November 03, 2018, 11:20:37 PM »
How do you calibrate the rain sensor please?


Offline tony

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Re: WS-2902A Rain Gauge Calibration
« Reply #3 on: November 04, 2018, 10:04:37 AM »
Thank you. i thought you could actually calibrate the sensor like you can on Acurite products.

Offline Buford T. Justice

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Re: WS-2902A Rain Gauge Calibration
« Reply #4 on: November 04, 2018, 02:22:26 PM »
87 appears to be too much correction so trying 88 now.

Offline platokidd

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Re: WS-2902A Rain Gauge Calibration
« Reply #5 on: February 24, 2019, 08:12:43 AM »
By how much over was your rain gauge?

Yesterday we had rain here and the ws2902a got its first real test. The total for the day was 1.75".
Checking on weather WU , most all other pws reporting had about .5".

So I'm thinking my totals for rain are way-off.

Is it possible to calibrate this enough to be in accurate?

Offline galfert

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Re: WS-2902A Rain Gauge Calibration
« Reply #6 on: February 24, 2019, 08:29:30 AM »
I wouldn't compare rain to any other station, much less what stations are on WU. If you want to calibrate then get yourself a manual rain gauge. Rain is hyper local. And most WU stations are poorly maintained and/or poorly sited.

https://www.amazon.com/d/Rain-Gauges/Stratus-Precision-Mounting-Bracket-Weather/B000X3KTHS/

I have a CoCoRah station about 5 houses down. We match rain fall to always within less than. 03 inches...and less on average and often we are spot on. I've not touched my rain calibration from factory. The difference I see could be just the difference in hyper local rainfall. If I care to know more then I'll get the manual gauge. But I'm not feeling like it is critical at this point.
« Last Edit: February 24, 2019, 08:43:54 AM by galfert »
WS-2000 & WS-2902A | ObserverIP | WeatherBridge (Meteobridge) | Ecowitt GW1000
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Tele-Pole flag pole is here (not installed yet)

Offline galfert

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Re: WS-2902A Rain Gauge Calibration
« Reply #7 on: February 24, 2019, 08:59:20 AM »
If anyone does decide to mess with rain calibration there are a few things to keep in mind. If you calibrate for a hard rain, where the tipping spoon design often has some rain loss. If you then calibrate for this loss, essentially then you are over compensating for the loss just to get the numbers you want on a hard rainfall. But then in a slow rain you'll be over reporting. So if you are going to calibrate do so on a slow or normal rainfall. Just accept that if it is hard rain then the nature of the tipping spoon is not going to be accurate and that there will be under reporting in that case.
WS-2000 & WS-2902A | ObserverIP | WeatherBridge (Meteobridge) | Ecowitt GW1000
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Tele-Pole flag pole is here (not installed yet)