SKY: power save mode = 2yrs+ battery life

Years of electrical, hardware, and software engineering has gone into the design and development of SKY to allow our precision sonic anemometer to operate on battery power alone. (Go ahead, do a google search for sonic anemometers – vast majority are wired and required external power.) No wires means better siting. Better siting means better data. In normal operating mode, SKY samples and reports the wind every 3seconds. With eight AA Lithium batteries, the power consumption curves should allow for 8-14 months continuous operation.

For those who want longer battery life, we’ve recently added the ability to toggle SKY into a power saving mode that samples and reports wind every 15seconds. This leads to roughly a 3 - 4X increase in expected battery life – which translates to 2yrs+ on a single set of AA batteries.

To enable power save mode:
App > Settings > Stations > [select station] > Manage Devices > [select SKY] > Advanced > Toggle on Power Save Mode


Please clarify if it’s 15 or 20 seconds.

Power Save mode is currently set at 15second sampling intervals. There was a previous thread where I mis-stated at 20sec.


Thank you. 15 seconds is actually better for us.

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How do we know when the Sky has low battery? The air has a panel in the app to see voltage, is there some kind of indicator for the sky?


on the webpage you should get a battery card for each with the voltages, same for the app

if not present, try toggling on and off the battery card option under advanced section of the station via the app.

@wxbrad App > Settings > Stations > select station > Advanced > toggle the ‘Hide Battery Card’ option.

PS - your SKY batteries are holding steady at ~3.4V. :slight_smile:

Just so I understand, does Power Save mode change how often the Sky ‘measures’ the wind or just how often it ‘reports’ to the Hub what it has measured ?

I notice that (in 3-second mode) rapid_wind data for max/min line up exactly with what the 60-sec obs_sky wind data reports, so other than making a cool gauge spin rapidly in gusty conditions, I’m thinking of going to power-save mode here maybe too.

In gusty conditions will obs_sky report the same wind values for that 60-sec observation period regardless of whether we set rapid_wind to work on a 3-second or 10-second period ?


According to what David has told us, it wakes up every 15 seconds, senses, transmits and goes back to sleep.

The 1 minute readings are based on the 3 or 15 second readings though I have not taken the time to actually use the 15 second readings to calculate the 1 minute reading.

A very good question and I look forward to David’s answer.


In default mode: SKY will wake up, measure the wind every 3 seconds, and send the instantaneous observation to HUB. HUB collects and pushes each 3sec ob to the WF cloud services. Then every 1min, HUB reports the lowest observed value as the lull, the highest observed value as the gust, and the average is calculated from the twenty obs the previous minute. This 1min data is stored in the WF cloud services whereas each 3sec ob is not stored.

In power save mode: SKY measures and reports wind obs every 15 seconds. HUB collects and pushes each 15sec ob to the WF cloud. HUB then uses the four obs collected in the previous minute to calculate and publish the 1min data which is stored by WF.

There are some other fancy algorithmic quality control checks that happen…but that’s another topic.


ok - bottom line is it wakes up every N seconds and measures, and the obs_sky is the reduced min/max/avg of what it observed. N is 3 seconds normally (20 measurements/minute) and 15 seconds (4 measurements/minute) in power-saving mode.



12 posts were split to a new topic: Power drain or weak batteries?

Which means people need to realise that in power saving mode the range of wind speeds between max and min each minute will be narrower due to less opportunity to detect the lowest lull or the strongest gust. I just thought that I would try the power saving mode between about 9:49 and 10:01 of this graph. (there is a slight delay before it actually changes mode)

It would also be simple to do a mathematical comparison to demonstrate the difference.
cheers Ian :slight_smile:


So are u losing hi wind gust putting it in power save mode ??

Hi @caredlands,
If you read the wind speed in normal mode every 3 seconds there are more readings to choose from. If you read the wind speed every 15 seconds in power saving mode there are only 4 readings to choose from. From those 4 readings which ever reading is the maximum will be the maximum reading for that minute. So if a gust of wind occurs at 9 seconds past the minute it will be recorded in normal mode but it will not be recorded in power save mode. So technically I would respond to your question with ‘yes’ you loose the hi wind gust.
BUT if the gust occurs at 15 seconds past the minute then you would not loose it.
Here is a video which demonstrates the 3 sec readings as a gust hits my Sky. If the 43 knot gust did not coincide with a 15 sec reading in power saving mode, then it would have been lost.

Does that help?
cheers Ian :slight_smile:

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so with 15 second interval your only getting 4 samples in a 1 minute period – so 1:00pm 00 seconds 1:00pm - 15 sec 1:00pm-30 sec 1:00pm- 45 sec as compared 3 second intervals you would get 20 samples in one minute

so it takes a reading every 3 seconds – like 1-2-3(reading) 4 - 5 - 6 (reading) 7 - 8 - 9 (reading) – so if at first 3 seconds gust is 15mph - however at 2 seconds a 25 mph gust occurs – only the 15mph will be recorded and the 25-mph will be lost is this correct

That is correct. It’s like taking a photo every 3 seconds.

so its better to set at 3 second sampling if its really windy – maybe power saving if its real still ----- how can u tell if you set it in power saving mode – is the bubble/circle pushed all the way to right or left — after setting – how long does it take effect – being put in or out of power save mode

Hi @caredlands,
If you wish to have the best quality wind data regardless of strength, for example I like to know ‘gust factor’ because it tells me how constant the wind is for my paragliding. During the sunny part of the day thermals cause gusts, and depending on your siting you may get turbulence gusts from obstacles up wind. And what is most informative to me is the maximum speed rather than the average. If your Sky is not high enough to clear upwind turbulence you might find the maximum speeds are closer to the actual wind speed than your average. So I use 3 second sampling to get a more accurate maximum gust speed. But if your Sky is difficult to lower from your pole you can decide to use power saving mode so that you dont need to replace the batteries so often.
You can tell when it is in power saving mode because the wind speed chages every 15 seconds. If it changes every 3 seconds it is in normal mode.
It takes a few minutes from changing the setting to when it changes its mode. Sometimes 2 minutes.
So it is possible to leave it in power saving mode until you need to know more accurate wind speed readings and change it. I hadnt thought of doing that. It might be a handy option because I only need accurate readings during daylight hours.

cheers Ian :slight_smile: