Measurement accuracy
The maximum error (error) in the distance data issued by the parking sensors during operation. Simply put, this is a plus or minus figure that must be assigned to the indicator data in the practical application of the radar (if a digital indication is provided at all, see "Functions / Capabilities"). For example, if an accuracy of 5 cm is specified, then if the display reads 50 cm, the actual distance from the sensor to the obstacle can be anything between 45 and 55 cm inclusive.
Note that there is nothing wrong with the very existence of an error — it cannot be completely eliminated even in the most advanced devices. Therefore, we are only talking about its meaning: the smaller the number indicated in this paragraph, the more accurate the readings of the parking sensors will be. High accuracy is especially important if you have to manoeuvre in very tight spaces where distances often approach the value of the minimum detection distance (see below). In this regard, also note that the claimed error values are relevant only for the operating range of distances.
Scan distance
Working distance range of parking sensors; in other words, this is the interval from the response threshold to the smallest distance at which the device is still able to provide sufficiently reliable data on the distance to the obstacle.
The threshold of operation of modern devices usually does not exceed 3 m, and more often it is in the range of 1.5 – 2.5 m; the sensors themselves are capable of providing a longer range, but in fact there would be little benefit from this, but there are plenty of reasons for unnecessary worries. The minimum distance, usually, is 0.1-0.3 m (10-30 cm); a closer entrance is usually perceived by the device as a close approach, with a corresponding indication (for example, the transition of the sound signal to continuous). And if the response threshold is more of a reference value, then you should pay closer attention to the minimum distance, especially if you often have to deal with cramped conditions (for example, manoeuvring at a difficult entrance to a small garage). Indeed, in such cases, it is important that the parking sensors retain the ability to accurately indicate the distance for as long as possible, without switching to the “close” mode.
Indication
A way to display information about the distance to obstacles, as well as about some other aspects of the parking sensors.
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Sound only. The simplest and least visual type of indication — data on obstacles are given in the form of an audible signal. Most often, these are intermittent signals that become more frequent as the sensors approach an obstacle and turn into a continuous squeak when approaching a dangerous distance (less than the minimum detection distance, see above). Audible-only models are inexpensive and also easy to install because the signal box does not need to be placed directly in front of your eyes. However, on their own, they provide only very approximate distance data and are more suitable as additional collision insurance than as a full-fledged “parking aid”. Therefore, many models of this type provide the ability to connect an external monitor (see "Functions / Capabilities"), which expands the display options. And options without such an opportunity are quite rare, mainly among low-cost models.
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LED bulbs. Indication using a set of LEDs (LED — light emitting diode); it can be not only spotlights, but also luminous indicators from rectangular blocks. Nevertheless, the general principle of operation is the same everywhere: the smaller the distance to the obstacle, the more lights are on; and in many models the indicators can be made in different colours, with those
...closest to the minimum distance usually made red. Such informing is much more visual than sound: usually, each light on / off indicator means a change in distance by a strictly defined value, which allows you to fairly accurately assess the situation. In addition, many of these models can be equipped with digital indicators (see "Functions / Capabilities"), and they are relatively inexpensive. As a result, LED bulbs are one of the most common types of indicators, especially in mid-range models.
— Display. The most advanced type of display, which implies the presence of a full-fledged screen. Parking sensors of this type are the most expensive, however, their functionality is very wide: after all, a wide variety of information, both digital and graphic, can be displayed on the screen, up to the “picture” from the reversing camera. However full-fledged displays (as in TVs, GPS-navigators, etc.) are the prerogative of premium-class devices. Simpler models usually have a design based on the so-called banners — ready-made inscriptions, pictures, etc., which are highlighted ("light up") in appropriate cases.
Note that the last two types of indication can be supplemented by a sound signal (and most often they are supplemented), and displays can be combined with LED indicators; in such cases, belonging is determined by the most advanced type of indication provided for in the design. It must also be said that the already mentioned digital distance indicator does not by itself turn the LED indicator into a full-fledged display — this requires other additional features.
