As you know, all of these wearable devices are functional and powerful. So, how are so many functions integrated in such narrow space of wearable Device. And What technologies are used in it? Now let me show you the answers about them.
First, how does it track your steps?
A wearable tracker continuously senses the movements of the body on a 3-axis accelerometer. The data of movement is recorded all the time. All this data is stored in the tracker for further processing.
The figure below shows a typical pattern of x-, y-, and z- measurements corresponding to vertical, forward, and side acceleration of a running person. no matter how the tracker is worn, at least one axis will have relatively large periodic acceleration changes. So, analyzing this data and detecting the acceleration period will give you accurate steps. Once it is worn and powered up, the tracker traces movement condition all the time, no matter the individual is walking forward, running fast, or even standing still.
Second, what technology are used to measure your heart rate?
The heart rate monitor on wearable Device is based on the technology called photoplethysmography. As the heart beats, it causes that volume of blood rises and falls in vessels as time go on. So, the heart rate can be monitored by measuring changes of blood’s volume.
And the frequency of the changes can be measured by photodiode and laser diode. As the light enters the skin from the laser diode, the photodiode gets reflection from blood. Because the strength of reflection changes as the blood’s volume, the monitor will get a time variant signal whose frequency is same as the heart rate.
So, this explains how the heart rate monitor works.
And third, how does wearable device assess your sleep quality?
Assessing sleep quality is much more complicated than measuring heart rate and motion. In order to evaluate sleep quality, it is necessary to know first what data the sleep quality is related to. So, a lot of information related to sleep should be gathered, including:
- Heart rate
- Body movement
- Muscle activity
- Brain waves (EEG)
- The movement of your eyes
- So on
But, Currently, most of wearable device can only monitored heart rate and body movement by the heart rate monitor and accelerometer. Wearable device will make analysis based on the heart rate data and body movement’s condition to assess person’s sleep quality.
Because the lack of data related to sleeping quality, the result of analysis about sleep, is not accurate enough and it is suspicious. If someone need to make a sleeping quality evaluation accurately, it is essential to seek doctor for help.
What’s more, there are other technologies applied in wearable device, such as：
- Wireless LAN
- Cellular network
- Beidou navigation
- NFC(Near Field Communication)
- So on
All of these technologies who I mentioned above, have a common point that they are not new technologies. But they are combined and used for new products and new scenarios.
So， old technologies get newborn.
下图显示了与正在运行的人的垂直，前方和侧面加速度相对应的 x，y 和 z 测量的典型模式。无论跟踪器如何磨损，至少一个轴将具有较大的周期性加速度变化。因此，分析这些数据并检测加速时间将为您提供准确的步骤。一旦佩戴和通电，追踪器就会随时追踪运动状态，无论个人是向前走，跑得快，甚至站立不动。