Comparison Amazfit Arc vs Xiaomi Mi Band 2

Types of sports and medical data collected by the gadget (plus some features of a similar purpose, such as sleep tracking, smart alarms, stress levels and women's calendar). Note that the features from this list can be found not only in specialized fitness trackers (see "Type"), but also in more traditional devices like smartwatches. Here are the most popular options:

— Pulse rate. Heart rate is one of the most important physiological parameters of a person. So that sports training is as effective as possible, the heart rate must be in a certain range (the specific value depends on the purpose of the training and the personal data of the user). And for some illnesses and treatments, a faster or slower heart rate can be an important signal, including a warning of danger.

— Pressure (tonometer). A sensor that measures the user's blood pressure. Note that the accuracy of such a sensor is usually quite low, the measurement error can be 10% or even more; so it will not replace a full-fledged medical tonometer. On the other hand, a gadget with this feature is quite capable of detecting a critical increase or decrease in pressure, which will allow you to take the necessary measures in a timely manner.

— ECG. A sen...sor that allows you to get detailed data about the work of the user's heart. Note that such a sensor is not a full-fledged electrocardiograph — in fact, it is an advanced type of heart rate monitor that can track the features of the heart rhythm. However, even this is enough to detect some dangerous phenomena — for example, atrial fibrillation, which at first is imperceptible to a person — and take appropriate measures in time.

— The blood oxygen. A sensor (the so-called pulse oximeter) that determines the saturation of the blood with oxygen (saturation); at the same time, the measurement is carried out by a non-invasive method — without punctures and other damage to the skin. Like most medical sensors in wearable gadgets, it is not accurate and is not a full-fledged medical device, but it is quite capable of responding to a critical decrease in the level of oxygen in the blood. It is believed that the presence of a pulse oximeter is relevant primarily for certain diseases, when saturation may decrease due to the disease itself or the characteristics of the treatment being taken. However, this feature can also be useful for quite healthy users who often travel at high altitudes — primarily climbers and aeronauts.

— Body temperature. The presence of a sensor for measuring temperature allows you to take measurements without the use of thermometers. Naturally, errors can occur, so a slight deviation from the norm may not be determined, but the device will easily fix a significant increase in temperature.

— T° of the environment. Even though smartwatches are worn on the body, the built-in sensors in them are usually designed to measure the ambient temperature. This information can be useful both for a general assessment of the surrounding conditions, and for specific purposes — in particular, weather forecasting. It is not uncommon for watches with this feature to also have a barometer (see "Navigation").

— Number of steps. The traditional pedometer is a feature for counting the number of steps taken by the user. These measurements usually use data from the accelerometer, and the results are quite accurate: most modern accelerometers are well calibrated and are quite capable of distinguishing tremors during steps from hand waves and other extraneous movements. The exception is trips in land transport: many wearable gadgets perceive shaking as steps, which should be taken into account when evaluating the results.

— Distance travelled. Measurement of the total distance traveled by the user. For this, either data from a pedometer or a GPS module are usually used (see "Navigation"); each option has its own merits. So, the pedometer is cheaper, it can be used even in rooms without windows, where the signal from satellites does not reach, and on simulators like treadmills, where the user does not move relative to the ground. GPS, in turn, gives higher accuracy, especially over long distances, and is not prone to false positives in vehicles. In some advanced gadgets, these methods can be combined — this is not cheap, but it allows you to combine the advantages of both options and achieve maximum accuracy.

— Movement speed. Determining the speed of the user's movement. As with distance travelled, measurement can be done in a variety of ways; see above for more details. Also note here that many gadgets with this feature are able not only to determine the current speed, but also to constantly record its value and display various indicators: the maximum achieved speed, the average value for training, etc.

— Energy spent (calories). Measurement of the number of calories burned by the user in the process of movement. These data are rather approximate, as they are calculated by indirect parameters (speed and range of movement, personal specs of a person, etc.). However, even this accuracy is quite enough to determine the overall effectiveness of training.

— The amount of fat burned. Measuring the amount of fat burned per workout. As in the case of calories (see above), the result of such measurements is quite approximate. However, in fact, absolute accuracy is not required, and fat loss data can be a powerful motivator.

— Activity time. A measurement of the total time during which the user is actively moving. In many models, such metering may provide additional options, such as fixing several periods of activity with breaks between them and determining the ratio between the time of movement and the time of rest.

— Smart alarm. An alarm clock that monitors the user's sleep phases and gives a signal to wake up at the optimal time for this. Human sleep consists of alternating phases, and waking up in the unfortunate phase creates a feeling of lethargy and fatigue, even if there was enough time to sleep. A smart alarm clock avoids such situations; its work is based on tracking the pulse, breathing rate and other parameters that differ depending on the phase of sleep. Note that the deviation of the signal from the set time can be up to half an hour, but this is usually a deviation towards an earlier rise. As a result, the risk of being late with a smart alarm clock is close to zero, and the lack of sleep time is compensated by the optimal moment of awakening.

— Sleep tracking. Sleep quality assessment is based on data from on-board sensors of fitness trackers or smartwatches. In particular, the heart rate monitor controls the number of contractions of the heart muscle, the accelerometer controls the user's movements. A blood oxygen sensor, if available on the wearable, improves the accuracy of sleep quality data collection. According to the readings of the sensors, the moments of entering and exiting the deep sleep phase are recorded. It is during this period that the restoration of the nervous system and the accumulation of energy for the coming day take place. In deep sleep, a person can completely reboot and gain strength, while in REM sleep, brain activity practically does not differ from the state of wakefulness. The sleep quality analysis feature helps you determine the best time to go to sleep and provides personalized recommendations to improve your night's sleep.

— The level of stress. The level of stress of the body allows you to evaluate the metric that determines the variability of the heartbeat — the difference in time between successive contractions of the heart muscle. Respiration rate, maximum oxygen consumption and excess oxygen consumption after exercise are also taken into account. The stress level score gives a clear picture of the user's experience during the day, however, the value of this parameter is in determining the most optimal body regimen for training. A high heart rate variability usually indicates you are in good shape for playing sports, while a low one can indicate fatigue, dehydration, or feeling unwell. All this directly affects the ability to train effectively. There are no clear units for measuring the level of stress — in smartwatches, the parameter is usually shown as a scale from 0 to 100, often indicating the number of hours the body is under stress and the time it takes to recover to a normal state.

— Women's calendar. The tool for tracking the menstrual cycle keeps abreast of the events of the expected dates of the menstrual period, allows you to determine the most favorable days for conception, helps to notice alarming symptoms in time and prevent many diseases in case of cycle disorders. Based on your total cycle length, the device calculates a predicted date for your next period. The women's calendar records cycle dates, fertility windows, and the day of ovulation. By adding your own notes to it, you can track fluctuations in sleep, appetite, fitness, mood changes and predict well-being for a particular day.

In addition to those described above, more specific types of measurements can be found in modern wearable gadgets.

The colour of the strap that the gadget comes with. If several options are indicated in this paragraph, this, usually, means that the user can pick the colour of his choice. Other options may be envisaged — for example, the presence of several straps in the kit, or the possibility of such a set at the request of the user — but they are much less common.

The type of clasp used on a gadget's strap or bracelet.

The most common types of clasps today are the classic buckle, folding clip, folding lock, magnet, snap fastener, and Hook-and-loop. If several options are indicated in the specs at once, it means that the gadget is supplied or can be supplied with different strap options using different types of fasteners. Here is a detailed description of each type:

– Classic (with buckle). Clasp resembling a belt buckle; originally used in traditional wristwatches, but nowadays it has become widespread in smart gadgets. On one half of such a fastener there is a U-shaped or similar frame with a special pin, on the second — a row of holes. When fastening, the second half is threaded through the frame, and the pin is fixed in one of the holes. At the same time, by choosing a particular hole, you can adjust the size of the strap. In addition, the advantages of the classics are reliability, neat appearance and compatibility with many strap materials (with the exception of metal bracelets).

— Clip (unfolding). An option for metal bracelets. The most widespread type of clip, consisting of two curved plates connected by an axis. When unfastened, they open like a book, increasing the overall length of the bracelet and allowing you to easily r...emove the watch from your hand, and when fastened, they fold close to each other and are fixed, securing the bracelet on your wrist. Another, less popular variety is the “butterfly”, which has two flaps that, when opened, rise like wings. In general, the clips are very easy to use, but difficult to set up. They fasten and unfasten with literally one click, but it’s impossible to reconfigure the size of a bracelet with a clip “on the go” — you have to disconnect and reconnect special latches, which requires an additional tool and some skill.

— Magnetic. A fastener in which a strong permanent magnet plays the role of a latch. Such devices are simple and convenient both in use and in adjustment: for fastening and unfastening, it is enough to “stick” or “unstick” a magnet, and size adjustment is carried out right at the time of fastening — by tightening the strap to the desired length. The main disadvantage of such a clasp is that it can only be used with metal bracelets made of magnetic alloys — for example, steel.

— With lock. A clasp that resembles the buckle described above, but has a slightly different principle of operation. On one side of the strap with such a clasp there is a latch pin, on the other side there is a loop of a D-shaped or other shape, as well as a number of holes. When fastening, the side with the pin is threaded into the loop and then fixed in one of the holes; By choosing one or another hole, you can adjust the length of the strap. This design is especially suitable for rubber straps, it is simpler and at the same time more reliable than the buckle, which can also be used with such straps.

— Hook-and-loop. Classic hook-and-loop closure, used exclusively with fabric straps. Like magnetic clasps (see above), such clasps allow you to very accurately adjust the length of the strap right in the process of fastening. Among the disadvantages of Hook-and-loop, in addition to restrictions on the materials of the strap, it is worth noting the tendency to reduce reliability as it wears out. Therefore, nowadays, this type of fastener is quite rare, and is almost never used as the only one available — usually Hook-and-loop is supplemented with another option, for example, a latch.

— Folding lock. Clasp in the form of a detachable lock, the halves of which are on different halves of the bracelet. It is used with finely woven metal bracelets, the so-called "Milanese" ones; at the same time, one half is fixed motionless, and the second can move along its part of the bracelet — in this way the length is adjusted. A tool may be required for adjustment, but the procedure itself is simple — much easier than with clips. And the low prevalence of folding locks is mainly due to the fact that Milanese bracelets are rarely found in smart wearable gadgets.

Wrist coverage suitable for the included watch strap. Usually, the length of the strap can be adjusted, so this paragraph usually indicates not one number, but a range — for example, "130 – 200" (millimetres). If there are several straps in the kit, then several ranges are indicated in the specs, if necessary, with a clarification like “fabric: 115 – 185, metal: 130 – 220” (if the straps are made of different materials).

We emphasize that in this case we are talking not just about the length of the strap, but about the girth of the wrist, for which it is designed. Thus, by measuring your hand in an appropriate way, you can accurately determine whether a particular strap is suitable for a particular person or not. This possibility is especially important if the watch is bought for a user with a non-standard hand size — miniature or, conversely, very large.

The degree of protection against water according to the WR standard, which corresponds to the body of the gadget.

WR (Water Resistant) is a rather specific standard that was originally used in traditional wristwatches. It describes the static water pressure that the device can tolerate without consequences: for example, WR30M corresponds to a pressure at a depth of 30 m (i.e. 3 bar). However, the physical features of such measurements are such that this figure corresponds very poorly to the actual allowable immersion depth. For example, the mentioned WR30M level only provides protection against accidental splashes, while the WR50M allows you to endure maximum exposure to rain or running water when washing your hands. The lowest level that allows complete immersion under water is WR100M, but only to a minimum depth and without “extreme” like surfing or diving from a tower. And for more serious activities, like water sports or diving, you should pay attention to gadgets with water protection at the level of WR200M, and even WR300M.

In most cases, the weight of the watch body itself is indicated as the weight of the model, since the strap is removable and can be replaced with another one. However, there are also models when the weight is presented with an included strap. Anyway, if the manufacturer indicates a specific method of measuring weight (with or without a strap), we add this information.