ALL ABOUT: Barometer – Why is it in smartwatches?

Tags: Technology and concepts | Smart

1.11.2021 | 5 MIN

It hung on the wall at your grandparent's house, and quite possibly it still hangs somewhere in your cottage. But what is this device doing in smartwatches?

What is a barometer?

Let's start with the basics... Barometer measures atmospheric pressure. The device was primarly used for forecasting the weather. Higher pressure usually signifies clear skies, when it slowly lowers, clear skies can turn into rain, and when the pressure drops quickly, we can expect a storm.

How does a barometer measure pressure?

The most commonly used barometer is the aneroid, also called the spring barometer. It was invented in 1843 by Lucien Vidi, and the principle is that it records the deformation of an air-empty box.

During pressure changes, the air vacuum shrinks and expands. Nowadays, of course, the display of values ​​is no longer analogue, but digital.

What is a barometric altimeter?

This device's name is usually shortened to just an altimeter and it serves to calculate the altitude of an object above a fixed level. A disadvantage of the barometric altimeter is its dependence on the weather (air pressure), so it is always necessary to enter a reference value (ideally the altitude at which you are currently).

Now we have specified what a barometer is, but let's focus on a barometer in smartwatches.

Only with a barometer can the watch record altitude meters in real time

This is probably the biggest reason why you should have a barometer in  a smartwatch.  If you hike or trail run and want to know about the ascended/descended meters in real-time, a barometer is a necessity. In other words – only a watch with a barometer will show you the ascent and descent from the start of the sport activity to its finish. Plus, if you are in a place with a bad GPS signal, barometer is much more reliable.

But be careful, it is necessary to calibrate the barometer before its every run. That can be done either manually (enter the current altitude according to the signpost, information board and others) or using GPS. The watch therefore finds out the current altitude using GPS data and takes this value as a reference.

How does a barometer record ascended and descended meters?

It is simple. The higher you are, the lower the pressure is. In laymen's terms, there is less air above you, and that is why the pressure is lower. So, as you ascend, the pressure drops, and the altimeter converts pressure changes to altitude meters. The same thing is happening when you descend. The altimeter converts the increase in pressure to descending meters. To give you an idea, air pressure averages 1013 hPa at sea level. In contrast, on Lysá hora at an altitude of 1323 meters, the air pressure is 872 hPa.

Is GPS enough to record the altitude?

Yes and no. But let's adjust the question a bit. Is GPS enough to measure the altitude in real-time? No. The point is that the elevation profile is analyzed only after saving the activity to the phone. Without the barometer, you won't be able to see the altitude in real-time. After you finish your sports activity, the data gets saved to your phone and analyzed, and only after that it tells you how many meters have you ascended and descended. But the analysis happens after the data gets saved and an internet connection is a necessity. Only with the barometer will you have real-time altitude meter data.

A watch with a barometer records the flights climbed during the day

Flights climbed is one of the most favorite lifestyle functions. It records floors by using a barometer, which based on the change in pressure recognizes climbing and then uses it to calculate the floors, where every 3 meters equals one floor.

Using the barometer to predict the weather

Yes, this utilization is actually the primordial and yet still current function of the barometer. You can predict the change in weather based on pressure changes.

What do the individual barometer values ​​mean:

• More than 1020 hPa – Constant, dry and sunny weather
• 1000-1020 hPa – Unstable weather, variable clouds with the possibility of precipitation
• Pod 1000 hPa – Expect rain, the lower the pressure, the more constant rainy weather
• Rapid drop in pressure is accompanied by stormy weather

It is the rapid drop in pressure that some smartwatches can detect and activate the storm alert. When the pressure drops quickly, the watch alerts you to the incoming storm.

If the pressure drops, how can I know if it's a climbing or a change in weather??

The question arises: When I climb to a higher altitude, where the pressure is lower, how do I know if its that the weather is getting worse or the pressure is just dropping because of the climb?

Most smart devices can convert air pressure to sea level. Meaning, it doesn't matter if you are on Mount Blanc or at the beach. The watch can recognize the altitude and take this value into account. If the watch doesn't recalculate this value, the universal rule is used, where every 100 m.n.m. is equal to 8 hPa.

So, if you are at the top of Lysá hora and the air pressure is 872 hPa, take the calculator and enter 13.23 x 8 and add this value to the original 872 hPa.You get a value of 977.84 hPa. So you can expect rainy and variable weather (as is often the case in the mountains).

But, as I said, most smart devices take the current altitude into account and recalculate the air pressure.

Is it worth having a smartwatch with a barometer?

You can get a record of altitude meters from a watch with or without a barometer. The only difference is that a barometer can record the altitude right when the activity is on. A watch without a barometer can do it only after the data is saved in the mobile app. So if you want to have an overview of the ascent, acclimatization or weather during the activity, it is useful to have a watch with a barometer.

Another factor is that the barometer always measures accurately regardless of external conditions. In contrast, the GPS receiver relies on signal range, which can sometimes be insufficient and deviations can occur (especially in dense forests and similar places).

Is it worth having a barometer in a classic watch?

I have decided to include this question because I know some people might be interested in it.  In most cases (in classic watches), the barometer appears in the Japanese brand Casio. The watches can measure the current air pressure, but cannot recalculate it to the current altitude. Therefore, it is a little more difficult to use the barometer in classical watches, as you have to know the pressure recalculations and at what altitude you currently are.