The smartwatch and fitness bands are very popular gadgets nowadays, they can do something more than just showing you a time such as they help us track our fitness activities, heart rate and sleep monitoring. But when it comes to heart rate monitoring, one question is always blowing in my mind: How does smartwatch measure heart rate? Or how smartwatch works to measure heart rate.
So, in this article, I’m going to share with you a piece of information about how smartwatches and fitness bands measure heart rate.
So with no further ado, let’s get started!
Before we dive in deeper, let’s understand what is heart rate?
In simple terms, a heart rate is a specific number of times your heart beats in a minute. It depends on what you are doing, if you are resting, it beats slower or if you are doing exercise; it beats faster. As you get older, changes in the rate and regularity of your pulse may change and may mean heart disease or some other condition that needs to be treated.
How Smartwatches or Fitness Bands measure Heart Rate?
If you are using the smartwatch of a fitness band, you might have noticed the green light and photo plethysmogram (PPG) sensor on the device. This green light and PPG sensor play’s vital role in measuring the heart rate.
Our red blood absorbs the green light and reflects red light, that’s why we see that most of the smartwatches or Fitness bands have green LED lights on the back of the device.
When the blood flows in hand, the smartwatch or fitness band flashes LED green lights hundreds of times per seconds, meanwhile the PPG sensor measures the number of heartbeats (heart rate) per minute.
Are you wondering how this PPG sensor works? Next, let’s understand how this PPG sensor works.
Photo plethysmography (PPG) is the process or technique to be used to detect the volume of blood flow in order to understand the change in heart rate through the skin. Traditionally, ECG (ECG) sensors have also been used to measure heart rate and detect rhythms, but ECG sensors are a bit bulky and cannot be used to detect heart rate when the body is moving. ..
Principles of photo plethysmogram (PPG)
As mentioned above, PPG uses low intensity infrared green (IR) light. As light passes through living tissue, it is absorbed by bone, skin pigments, and both venous and arterial blood.
Light is absorbed more strongly by the blood than the surrounding tissue, so the PPG sensor can detect changes in blood flow as changes in light intensity.
The voltage signal from PPG is proportional to the amount of blood flowing through the blood vessels. This method provides greater accuracy because even minor changes in blood volume can be detected.
How does this technology work?
According to the Valencell, the smartwatches or fitness bands use four major components :
Optical emitter
Digital Signal Processor (DSP)
Accelerometer
Algorithms
Optical emitter The optical emitter typically includes at least two LEDs that transmit light waves into the skin or wrist. Due to the enormous differences in skin tone, thickness and morphology associated with the diversity of consumers, most OHRMs use multiple wavelengths of light that variably interact with different levels of skin and tissue.
Digital Signal Processor (DSP)
When the light transmits into the wrist through the smartwatch, some lights reflect towards the sensor which includes the Digital Signal Processor (DSP) that that detects the light and converts those signals to another zero which can be measured into meaningful data of the heart.
Accelerometer
Accelerometers measure motion and input to the PPG algorithm along with DSP signals.
Algorithms The algorithm processes exercise-tolerant heart rate data such as VO2, calories burned, RR interval, changes in heart rate, blood metabolism levels, and blood oxygen level signals from DSPs and accelerometers.
Are Smartwatches accurate for heart rate?
The smartwatches or fitness bands are most likely they are not accurate as compared to professional medical devices. But they will be nearly closer to measuring the heart rate, not precisely accurately. So it is recommended for you to not rely completely on this kind of device for critical monitoring instead of the doctor.Most of the time smartwatches and fitness bands fairly measure accurate heart rate, but it is not a means to use this device for critical heart rate monitoring. You can use these kinds of wearable devices as features, not for the medical equipment. I hope this piece of information helped you understand the functionality of the smartwatch and fitness tracker’s heart rate monitoring.
