Cumulus Support

This was unexpected!

I finally got round to mounting the WS80 on top of my 10 metre pole along with the VP2.

I was expecting the WS80 gust values to exceed the VP2, however this is what I am getting - I have deliberately chosen a day where there was a calm period over night. As you can see the VP2 is consistently measuring higher gust speeds than the WS80. It is only when the wind dropped below 4 mph that I see the WS80 consistently giving higher values.

Next looking at the average speeds for the same day, the WS80 is reading quite a bit lower than the VP2. That is until the wind speed drops below 2 mph, when the WS80 again tends to give higher values. Finally I did a sanity check that the WS80 wind speeds being recorded by CMX agreed with those on Ecowitt.net.
You can see that they agree, within the bounds of Ecowitt.net using a 5 minute average period, and CMX using a 10 minute average. I'm not sure what to make of this yet, but I thought it was sufficiently interesting to share these early results.

Indeed, interesting and unexpected.

I never had both running side by side and always had the feeling the WS80 was too high and it took me 6 months before I settled with the device and agreed with the data. I must say the storms we had this year did not help: since the first storm we had a lot of wind on average and though it felt as a lot of wind I had a difficulty believing the numbers. Switching the devices around that time did not help

This exercise helps in accepting the ws80.
I must say that the 'flatlining' and other errors which needed to be fixed did not help. Good to see everything is a bit calming down and that the numbers are OK.

Thanks for the exercise

I have also seen cases where the WS80 seems to give higher gust values than the VP2, these results have now sown the seeds of a thought that they may be inconsistent?

One thought was that the calibration of the WS80 was out, but the fact that it reads higher speeds in near calm conditions seems to rule that out, you expect it to drop to zero like the VP2 if it were under reading.

The low speed response is fantastic - no more worries about the physics of inertia!
Your other findings are, as you say, unexpected. Do you have a correction factor on the mechanical sensor? If not, then the only reason I can think of is that the software within the ultrasonic device needs calibrating.

mcrossley wrote: ↑Mon 09 May 2022 4:12 pm One thought was that the calibration of the WS80 was out, but the fact that it reads higher speeds in near calm conditions seems to rule that out, you expect it to drop to zero like the VP2 if it were under reading.

Not necessarily, as the measurement is software calculated it could easily have different calcs for different speed ranges. We would need to see the software to know that.

freddie wrote: ↑Mon 09 May 2022 4:50 pm The low speed response is fantastic - no more worries about the physics of inertia!
Your other findings are, as you say, unexpected. Do you have a correction factor on the mechanical sensor? If not, then the only reason I can think of is that the software within the ultrasonic device needs calibrating.

Not sure how to calibrate the software but it would not surprise me if Ecowitt would fine-tune its firmware and we would see some upgrades in future (as we had already)

freddie wrote: ↑Mon 09 May 2022 4:50 pm The low speed response is fantastic - no more worries about the physics of inertia!
Your other findings are, as you say, unexpected. Do you have a correction factor on the mechanical sensor? If not, then the only reason I can think of is that the software within the ultrasonic device needs calibrating.

No calibration factors in place for either device - other than a 180 direction shift for the WS80 as it has to stick out the south side of my pole. But that means it is clean air for our predominately S-SW winds.

Firmware upgrades on the WS80 are something I'd dread, I hate working at height on a ladder with no protection! They would also mean unbolting the WS80 and bringing it indoors to update via USB - a major undertaking, so I hope they do not update too often!

And to complete the set, here is a comparison of the average wind direction (10 mins) for the VP2 and WS80...
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Interesting exercise Mark. I suspect many of us who have our anemometer positioned on the roof would love to have one that never needs attention.

But if firmware updates can only be applied to the sonic version by accessing it where is the advantage? The latest Hall-effect anemometer with a cartridge replacement is the best yet and hopefully will last a very long time. But it will need some attention from time to time so both of them require access for different reasons.

What’s the advantage of the sonic over the current model? It’s lost on me.

RayProudfoot wrote: ↑Wed 11 May 2022 5:20 pm What’s the advantage of the sonic over the current model? It’s lost on me.

No moving parts.
Excellent low speed response.
Theoretically will record more accurate gust speeds.

freddie wrote: ↑Wed 11 May 2022 6:49 pm No moving parts.
Excellent low speed response.
Theoretically will record more accurate gust speeds.

That wasn’t obvious in Mark’s evidence. Is the response time better than the conventional anemometer of 2.5 secs. That would be of interest.

RayProudfoot wrote: ↑Wed 11 May 2022 6:58 pm

freddie wrote: ↑Wed 11 May 2022 6:49 pm No moving parts.
Excellent low speed response.
Theoretically will record more accurate gust speeds.

That wasn’t obvious in Mark’s evidence. Is the response time better than the conventional anemometer of 2.5 secs. That would be of interest.

If you're thinking of the Davis 2.5 second polling time, then no that won't change. It's more to do with the frictional effects at low speeds, and more accurate gusts due to absence of any inertial physics effects.

Thanks Freddie.

The WS80 updates every 4.75 seconds, the new WS90 updates every 8.8 seconds (it's not clear to me yet if the WS80 will be discontinued when the WS90 is generally available).

For me I think the VP2 cups are a better option. No batteries to change, recalibration, or firmware updates required.

I thought Ray was talking about the Davis ultrasonic anemo?