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How far away can an rfid tag be read ?

How far away can an rfid tag be read ?

What is the working principle of rfid UHF tags?


When the reader emits electromagnetic waves, the electromagnetic waves propagate in the air, the farther the distance is, the greater the attenuation, and then the electromagnetic waves reach the tag position, the tag antenna cuts the magnetic induction line to generate a pulse current, and the current is supplied to the tag chip. If this energy is not enough to activate the tag chip , the performance is that the tag cannot be read. If it can be activated, the tag will work and return a pulse current to the antenna of the tag. The antenna is converted into a pulse current to the read-write module. If the reader-writer has a high receiving sensitivity, it can detect such a small amount of energy and successfully analyze it. At this time, the tag is read out. If the energy is too weak, the reader-writer If you can't feel it, you won't read the label.



Therefore, the working distance of the RFID UHF tag is related to the reader, the RFID tag, and the application environment. Different application places use rfid equipment with different performance, and the effect achieved is inconsistent, so it needs to be purchased and configured according to its own needs.



What factors affect the reading distance?


  1. Reader: The transmitting power of the RFID reader affects the reading and writing distance. The greater the transmitting power of the reader, the greater the reading and writing distance.


  1. Antenna: The antenna gain and beam width of the RFID reader affect the reading and writing distance and range. The greater the antenna gain and the smaller the beam width, the longer the reading and writing distance


  1. Tags: RFID tags are divided into active RFID tags and passive RFID tags according to the power supply status.


Active RFID tags: It is powered by a battery, has a longer reading and writing distance, and is larger in size. Compared with passive RFID tags, the cost is higher.


Passive RFID tags: Passive RFID tags have no batteries, are low in cost, have a long service life, and have a relatively short reading and writing distance.


The size of the RFID tag also affects the reading and writing distance. In theory, the larger the size of the RFID tag, the farther the reading distance can be.


  1. Feeder: It is related to the attenuation of the feeder unit. The larger the attenuation, the closer the reading and writing distance. On the contrary, the smaller the attenuation, the longer the reading distance; it is also related to the total length of the feeder connecting the reader and the antenna. The longer the feeder, the shorter the reading distance. The shorter the writing distance, on the contrary, the shorter the feeder, the longer the reading distance.


  1. Environment: The environment mainly refers to whether there are obstacles (metal, liquid, etc.) between the RFID reader antenna and the tag, and whether there is electromagnetic interference with close frequency in the environment. The signal of the RFID tag can penetrate non-metallic or non-transparent materials such as paper, wood and plastic, and can be recognized through penetration. However, metals and liquids will affect electromagnetic waves and affect the reading and writing distance. If it passes through metal or liquid, it will affect the reading distance, or even fail to read. In this case, metal and liquid resistant labels are required.


Generally speaking, we usually say how many meters the reader can read. In fact, this is only the data measured under a specific condition and environment. Without this specific environmental condition, such a number is strictly meaningless. It can be used as a reference. In addition, UHF RFID is not only suitable for long-distance applications. In fact, it can be used from zero distance to long distance, and the closer the distance is, the easier it is to achieve, but the cost is relatively high.




How far away can an rfid tag be read ?


125 kHz and 134.3 kHz low frequency (LF) passive RFID tags


The read distance is 30cm or less - usually 10cm unless you are using very large tags, when the tag is attached to metal the read distance can be up to 2m. Several different LF 134.2 tags with a read distance of 1-2m in an industrial environment. There are also special readers that allow reading distances of 1-2 meters with standard size tags, so there is no limit.


13.56 MHz High Frequency (HF) Passive RFID Tags


Maximum read distance of 1.5m - typically under 1m, and you can use single or multi-port readers and custom antennas to extend the read range to longer tag read distances or larger RFID read areas . To get a distance above 1m you need a reader that has an RFID output power above 1 watt. We can provide up to 10 watts of RF power output for 13.56 readers for multiple antenna connections and a tag reading distance of more than 1 meter.


860~960 MHz Ultra High Frequency (UHF) Passive RFID Tag


The minimum reading distance is over 1m or 0.9m. Gen 2 tags can be 860 MHz or 902 MHz. FCC depends on labeling capabilities and other features. Second-generation semi-passive (semi-active) tags are battery-assisted and have a read range of up to 50m. Of course, for customers with specific needs, we can also provide passive and emerging semi-active readers and tags.


RTLS - Real Time Location System


Usually LF and SHF. Need to have UHF RTLS that is very accurate and can be easily controlled on a single switch within a range of 23225m2.


433 MHz Ultra High Frequency (UHF) Active RFID Tag


Using our special high-gain antenna solution, a fully adjustable read range can be achieved from 30cm to 3km. A line of 433 MHz fixed and portable readers, tags, antennas and accessories are available in the market for a wide variety of industrial, marine, healthcare, mining, vehicle, personnel and other tracking and location applications.


2.45 GHz Super High Frequency (SHF) Active RFID Tags


The maximum reading distance is 100m. There are several different modulations for 2.45 GHz. And you can also get real-time location information from these active tabs.



  How to determine the range obtained from RFID?


RFID is a radio frequency technology, usually identified by the frequency or "wave" it uses. The maximum distance you will reach is affected by:


  • The operating frequency (or bandwidth, if there are multiple frequencies) of the RFID system
  • Reader settings for RFID readers and systems
  • Antenna - type, gain (dBi), center frequency, VSWR, polarization, size, IP rating
  • Characteristics of RFID tags - size, shape, polarization, tuning
  • The thickness and material the label is attached to
  • Materials to which RFID tags are attached
  • Orientation of RFID tags and reading antennas
  • Things to attach labels to - adhesives, tape, staples, rivets, screws
  • The environment in which the RFID solution is located


...and several other factors. This kind of is why some RFID vendors offer a "free space" read distance with 12 dBi antenna gain, allowing you to get good RFID reads at "that critical distance". Any e-cloud RFID tag reading specification is based on actual RFID tags in use, not "free space" using our OEM handheld readers as "free space" and "12 dBi gain" are not at all in most RFID environments Can't be achieved.

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