Topic: Rain multiplier for GW1000

[canlab]

I noticed that my Ecowitt rain gauge is reading high compared to my regular rain gauge. I'm wondering what other people are using for a multiplier in the software? As well, I'm using Cumulus MX which also has a multiplier. Do I set them both the same in the Ecowitt software and Cumulus? Or will that be a multiplier on multiplier?

[doubleohwhatever]

I would set the multiplier on the GW1000 only. You need to set the multiplier based on the amount your station is over or under reporting.

What rain guage are you using as your reference?

[canlab]

I have an old fashioned manual cone shaped plastic one that you can stick in your lawn. Last night it showed a little over 9/10s. My Ecowitt showed 1.6 inches. I really feel that we didn't get that much.

[doubleohwhatever]

It definitely sounds like your Ecowitt station is over-reporting. However, before you do anything else, I would double check that the Ecowitt station is level.

Once you've ensured that your Ecowitt station is level, I would log the results of several rain events from both your reference gauge and your ecowitt station. If the difference between the two is roughly the same percentage over a number of rain events then a multiplier can be applied to resolve the problem. However, if the Ecowitt is varying wildly then there may be something wrong with it. A couple of notes:

1) Make sure that your reference gauge is accurate. If you're confident your gauge is accurate then you're all set. If not then I'd look at getting something like this: https://weatheryourway.com/collections/cocorahs-gauge-parts/products/official-cocorahs-gauge

2) Try not to use very heavy rain events or very quick rain events for comparing. Tipping buckets tend to under-report during very heavy rain events and would result in you calculating a multiplier incorrectly. Very light rain showers may only result in few tips which would not be enough for a solid comparison. A constant but meaningful rain event is ideal for comparing (won't overwhelm a tipping bucket but gives enough rain for comparing).

3) I know this sounds a bit drawn out and complicated for what it is. However, based on your numbers of 0.9 and 1.6, your Ecowitt station is over-reporting 75-80%. That's not normal. I suspect either the Ecowitt station is not level, your reference gauge is not accurate, or something is wrong with your Ecowitt station. However, if your reference gauge *is* accurate and the over-reporting percentage *is* roughly the same over several rain events, then a multiplier will solve the problem regardless of what's causing the over-reporting.

4) If your Ecowitt station is level, is still covered by the warranty, and you know your reference gauge is accurate, then I'd contact Ecowitt.

[davidefa]

You can also check that there is no dirt inside, where the tipping mechanism is, and that it moves as it should

[Rover1822]

Along with the items mentioned.

1) When comparing 2 rain gauges they need to be as close as possible to each other without interfering with each other, this includes height.

2) It is very important that the Ecowitt , and all tipping bucket style rain gauges be on a firm a mount as possible. Vibrations or movement of the pole or mount can cause the bucket to tip early as the bucket fills resulting in a higher rain total.

As far as the calibration, you shouldn't have to calibrate the rain gauge. If you do end up calibrating, do it only at the host console. Any other calibrations applied will be additive and throw everything off .

If you can, fill your manual rain gauge to a level, then very very slowly (like drip by drip) decant the manual rain gauge into your Ecowitt. Then read values. Note of course, that testing like this will affect your totals anywhere you are saving them, so only do it if that is not important.

Also what model Ecowitt rain gauge and console are you using?

[davidefa]

If you can, fill your manual rain gauge to a level, then very very slowly (like drip by drip) decant the manual rain gauge into your Ecowitt. Then read values. Note of course, that testing like this will affect your totals anywhere you are saving them, so only do it if that is not important.

This will work only if the two rain sensors have the same collecting area

[mauro63]

Along with the items mentioned.

1) When comparing 2 rain gauges they need to be as close as possible to each other without interfering with each other, this includes height.

2) It is very important that the Ecowitt , and all tipping bucket style rain gauges be on a firm a mount as possible. Vibrations or movement of the pole or mount can cause the bucket to tip early as the bucket fills resulting in a higher rain total.

As far as the calibration, you shouldn't have to calibrate the rain gauge. If you do end up calibrating, do it only at the host console. Any other calibrations applied will be additive and throw everything off .

If you can, fill your manual rain gauge to a level, then very very slowly (like drip by drip) decant the manual rain gauge into your Ecowitt. Then read values. Note of course, that testing like this will affect your totals anywhere you are saving them, so only do it if that is not important.

Also what model Ecowitt rain gauge and console are you using?

1) When comparing 2 rain gauges they need to be as close as possible to each other without interfering with each other, this includes height.

Uhm, I don't think, not too close, one of the most important error is due to the wind, if the rain gauge are too close to each other, only one of them, depending on wind direction, will have a bigger error, obviously in high wind rain events

Mauro

[Rover1822]

Grin, I should have mentioned that more explicitly when I said don't interfere

[mauro63]

Grin, I should have mentioned that more explicitly when I said don't interfere

It's okay, only a clarification, is not possible to eliminate interferences if the two rain gauges are strictly close to each other

Mauro

[Rover1822]

ACCCK I made an omission

"If you can, fill your manual rain gauge to a level, then very very slowly (like drip by drip) decant the manual rain gauge into your Ecowitt. Then read values. Note of course, that testing like this will affect your totals anywhere you are saving them, so only do it if that is not important."

Don't do this without doing the rather complicated math on both the manual and Ecowitt gauges to find out what volume equates to an inch, or amount of rain per area etc. Cone size area for both is required to come up with an equation. (you may want to just skip this altogether as far as a test).

Surprised Mauro didn't jump on me for this.

[canlab]

Thank you for the very informative information! It is an Ecowitt HP 2551 and is dead level according to the little level on top. However I may have found the problem. Upon inspecting the rain gauge I noticed a small accumulation of dirt in the bottom of the spoon. I would assume that may cause it to tip early? In your collective experiences do you consider these rain gauges to be reasonably accurate?

[Rover1822]

Thank you for the very informative information! It is an Ecowitt HP 2551 and is dead level according to the little level on top. However I may have found the problem. Upon inspecting the rain gauge I noticed a small accumulation of dirt in the bottom of the spoon. I would assume that may cause it to tip early? In your collective experiences do you consider these rain gauges to be reasonably accurate?

"reasonably accurate?" , loaded question . depends on use and individual. I do find them reasonably accurate for price point etc.

Dirt can cause it to tip early, if the dirt has a higher density than the water, as the bucket tips on weight.

[doubleohwhatever]

Upon inspecting the rain gauge I noticed a small accumulation of dirt in the bottom of the spoon. I would assume that may cause it to tip early?

Yes, that could be the culprit. Let us know how it performs after cleaning.

In your collective experiences do you consider these rain gauges to be reasonably accurate?

The accuracy of the rain guage on your Ecowitt station is specified to be plus or minus 10%. With such a small rain bucket, I'm not sure much better accuracy can be expected. I would say it is reasonably accurate for the price point.

Where the Fine Offset (Ecowitt, Friggin, Ambient, etc) really excell is in value. They make weather stations affordable for a large number of people and anything that gets people into the hobby is a good thing. However, I do firmly place them in the consumer category.

If Fine Offset were to ever create a more expensive and professional grade station, I think they would give Davis a challenge in the non-agricultural low-end professional segment.