First, i test the sleep tracking using an eeg monitor. Second, i test the heart rate accuracy and finally, i take a look at the spo2 sensor. As always, i do not want to waste your time, so timestamps are in the description below and also on the timeline, hello, everyone for those of you that are new to the channel. My name is rob and im a postdoctoral scientist specializing in biological data analysis. The redmi watch 2 light just got released in europe and just looking at the device and interacting with it, the bigger screen and better touch screen make it feel slightly more premium than the original mi watch light. However, how good is it attracting different health features? In my test, the mi watch light was mediocre at best showing some issues in heart rate tracking and also not including ram sleep tracking. Luckily, the new redmi watch – 2 lite does include rem, sleep tracking, so lets take a look and see if its any good for the sleep test. I wore the redmi watch 2 light to bed for 3 nights and at the same time i also wore this eeg device called the dream. 2 headband and finally, i recorded myself using an infrared camera. Now the eeg device can actually measure your brain waves and is therefore ideal for measuring your sleep stages. Additionally, a scientific paper showed that the dream to headband is good at measuring your sleep stages. Lets take a look at those results.

Lets start by checking if the redmi watch too light predicts the correct sleep stages at the right time, and that is what is displayed here. On top, we have the sleep stages according to the eeg device and on the left, the sleep stage, according to the redmi watch 2 light. Now each column here sums to 100, meaning that we can see what percentage of each of the actual sleep stages was recorded. As the sleep stage by the redmi watch, 2 light ill highlight all of the stages that are correctly predicted in green as im explaining the results. First of all, we see that 98 of what was deep. Sleep was also predicted as being deep sleep by the redmi watch to light so thats pretty good. Almost all of the deep sleep was also detected as being deep sleep. Take this example knight, for instance, with the four deep sleep segments i had marked them purple. On top, you can see the sleep stages as they were recorded by the eeg device on the horizontal axis. We have the time of night and on the vertical axis, are the different sleep stages that being deep sleep, light sleep, rem, sleep and awake on the bottom. You can see a similar plot, but now for the sleep stages as they were recorded by the redmi watch 2 light. Here we see that the redmi watch 2 light did indeed detect all of my deep sleep. However, it also predicted some extra deep sleep.

While i was actually in light sleep for the most part, however, all in all this doesnt look too bad. Now this is his second night, and here we again see that all of my deep sleep was detected. However, we also see that a lot of extra deep sleep is detected usually in moments when i had light sleep – and we see the same for this final night right here. Basically, all of my deep sleep is detected, but also a lot of extra deep sleep is recorded. While i was actually mostly in light sleep next looking at light sleep, we see that about half of the light sleep i had was correctly detected as light sleep. However, a lot of it was actually detected as being deep sleep. This reflects what we saw for the individual nights, where we saw that a lot of extra deep sleep was detected now rem, sleep detection does not seem great. With less than half correctly predicted ram, sleep was actually quite often confused. With light sleep, we see the same thing looking at the individual knights. However, interestingly, the positioning of the ram segment seems to be quite okay with all four ram sleep segments here detected to some degree, and we mostly see the same for the second knight right here. With a rough agreement in the positioning of the ram sleep segments of the redmi watch, 2 light and the dream to eeg headband only for this third knight right here was it a bit more off.

So we actually see a lot more missing ram sleep for the redmi watch, 2 light for this knight. Now, because the positioning of the ram sleep segments is quite ok, we can also often roughly see the sleep cycles based on just the data from the redmi watch to light to see the sleep cycles. I added non rem, sleep in blue and again marked ram sleep in red. Each sleep cycle starts with a combination of deep sleep and light. Sleep together called non ram and always ends in ram and, as you can see here for this night, the cycles roughly agree. We see the same thing for the second night, where we can mostly see the sleep cycles based on just the data of the redmi watch 2 light only for this third knight right here would, i say, its a bit more difficult to see. Awake detection is quite okay, with about 70 of my awake moments correctly detected. If they were confused, they were mostly confused with light sleep, which makes sense since light sleep is the closest sleep stage to being awake thats. Also, what we see when we look at the individual nights here we see that most of my long awake moments were indeed correctly detected, though, for the second night right here, surprisingly, one of my awake moments was actually detected as deeply by the redmi watch. 2 light for this final night, the results are much better again with most of my awake moments correctly detected.

So how do these results? Compare to the results i got for the original mii watch light when i tested it. Lets have a look that is displayed right here on the left. We have the results we just saw and on the right we have the results for the original me watch light. As you can see, the mii watch light could not detect ram sleep. Deep sleep detection is a lot better for the new mi watch light, though light sleep protection is actually possibly a bit worse and though awake detection has a slightly lower percentage. I expect it to be roughly the same. I think the main improvement is the inclusion of ram sleep and the results actually make some sense. We can see a lot of the sleep cycles based on just the data of the redmi watch 2 light and, of course, the bigger screen of the redmi watch. 2. Light looks a lot better than the screen of the original mi watch. Light next lets put all of this into context by comparing the redmi watch 2 light to some of the other watches i tested in the past. That is displayed right here now. This graph contains a lot of information, so let me try to explain what you see along the horizontal axis. We have the average accuracy over the four different sleep stages, that being deep sleep, light sleep, rem, sleep and awake along the vertical axis. We have the accuracy of the worst sleep stage at a distance.

Many devices compromise the accuracy of one sleep stage to benefit the accuracy of the others. This graph uses a dream: 2 headband as a reference and a better device, the more to the top right in this graph. It is, as you can see, based on these metrics. The best devices are different: fitbits, the whoop, strap 3.0 and 4.0, and the within sleep analyzer. The redmi watch 2 lite, definitely underperforms a bit when it comes to these best devices. However, its not terrible for the price it performs about equally well as the ordering when it comes to sleep tracking. However, unlike the ordering, it is able to track my sleep cycles, at least for the most part, so this is looking okay for the redmi watch. 2. Light for the price, its honestly, not bad. Next lets take a look at the heart rate: accuracy to test the heart rate, accuracy ill. Compare the redmi watch 2 lite to the polar h10 ecg chest strap, which is generally considered one of the most accurate consumer devices available for hardware measurements lets start with the accuracy during spinning. Here i displayed an overview of the heart rate accuracy during a total of three spinning sessions. Each dot here is a single heart rate measurement with long the horizontal axis, the value according to the polar h and hg chest strap along the vertical axis, the value according to the redmi watch too light, the blue line indicates perfect agreement, so any measurement along this Line at roughly the same value according to the polar h10 chest strap and the redmi watch 2 light the more measurements there are in a certain area, the darker black, the color, and, as you can see, the redmi watch to light mostly agrees with the chest.

Strap, as most points are along the blue line. However, there are also quite a few points away from the blue line and we see the same if we look at the individual spinning sessions along the horizontal axis. Here we have the time and my heart rate is along the vertical axis in blue. I uploaded my heart rate: according to the polar h10 ecg chest, strap and in red is my heart rate. According to the redmi watch, 2 lite, as you can see, overall, the devices agreed pretty well. The redmi watch to light often has a slight delay in picking up my increase and decrease in heart rate for the second ride. We see mostly the same thing. There are slight delays in picking up decreases and increases in my heart rate, and there might be a bit more instability in the higher heart rate ranges and thats also what we see for the third ride, overall, decent agreement with some instability and some delays. Overall, these results are not bad. Next lets take a look at cycling outside which i recorded whilst commuting to and from work. If i cycle outside, there are many more bumps which might also influence the accuracy of the redmi watch. 2 lite lets have a look here. We see an overview of those measurements similar to before. However, now there are quite a few more points below the blue line indicating that the watch detected the too low heart rate.

If we look at the individual bike rides, we indeed see that the redmi watch to light after detected to low heart rate. We see the same thing for the second right right here, where the heart rate is almost always too low. Now this third ride is a bit better. There are still plenty of moments where it struggles thats. Also what we see for this fourth route right here, sometimes theres, a good agreement, and sometimes the agreement is less good. Next lets take a look at a weightlifting session. Now weightlifting is one of the hardest things for watch to accurately track since theres much more tension on my arm and wrist. As you can see, in this overview in the higher heart rate ranges, there are quite a few points below the blue line, which means it detected it too low heart rate, when my heart rate is actually quite high. We see the same in this example weightlifting session. You can see that the devices do not agree very well. The redmi watch 2 light is not able to pick up on the increases. In my heart rate, the company said that i did – and we can see the same in this second session right here, where it was able to follow the general patterns, but not the peaks. In my heart rate, the heart rate tracking of the redmi watch 2 light appears to be okay. It works well enough during relatively static cardio exercises.

However, where theres more movement involved, it struggles quite a bit more next lets take a look at the oxygen saturation measurements in really simple terms. Your oxygen saturation or spo2 is the percentage of red blood cells in the bloodstream that contain oxygen. Normal ranges are generally between 95 and 100 percent, and these are the values you should normally have at ground level to test that over the last few days, i took a total of 19 measurements of my spo2 levels, with both the redmi watch 2 light and the Dedicated spo2 monitor in the morning and in the evening the results are displayed here on the left are the values measured by the redmi watch 2 light and on the right. The value is measured with a dedicated finger pulse exhibitor. As you can see, the redmi watch 2 light detected much lower spo2 values than the dedicated oxygen saturation sensor. It even had some values at or below 95, which i generally do not have at ground level. All in all, i would not completely trust the values reported by the spo2 monitor of the redmi watch 2 lite, at least not by measuring relatively normal values in previous videos. I also tested the spo2 accuracy of different watches in a low oxygen environment, which is a test id also like to do for the redmi watch too light in the future. All in all, i was not disappointed by the redmi watch 2 light, but also not blown away.

It performed okay at sleep tracking and was significantly better than its predecessor. The heart rate tracking was not amazing and can only really be used during static, cardio workouts. The spo2 sensor is something i would not rely on personally, however, for the price overall, its not bad, it looks and feels better as a bigger screen and a more responsive touchscreen than the previous mii watch light. Every interface still feels kind of sluggish when using it, and the watch also has a slight delay when turning on the screen out of sleep mode. So should you buy the redmi watch 2 lite? Well, that really depends if you just want to track some basic sleep and heart rate parameters. I think it might do the job. However, you should not expect the same smartwatch performance of more premium watches like garmin and apple, and you will also not get the sleep tracking quality of fitbit. I personally still prefer the me watch over the redmi watch 2 lite, and if you want to see that review check out this video right here, as always, it helps the channel.

https://www.youtube.com/watch?v=MlMFRveZHUk