RFID reader FAQ

- Jan 27, 2019-

The receiving range of the reader is affected by many factors, the frequency of the radio wave, the size and shape of the tag, the energy of the reader, the interference of metal objects, and other radio frequency devices. In general, low-frequency passive tags are received within one foot of the distance, three-foot for high-frequency passive tags, and ten to twenty feet for UHF tags. For semi-active and active tags that use batteries, the reader can receive signals of three hundred feet or more. For low frequency and high frequency RF, if the tag is the same size as the reader antenna, the receiving distance can be calculated by multiplying the diameter of the antenna by 1.4. This rule applies to diameters within thirty centimeters.

What do LF, HF, UHF stand for?

As with the radio we listen to, the RF tag and reader must be modulated to the same frequency to work. LF, HF, UHF correspond to RF at different frequencies. LF stands for low frequency radio frequency, around 125KHz, HF stands for high frequency radio frequency, around 13.54MHz, UHF stands for UHF radio frequency, in the range of 850 to 910MHz.

Why use different frequencies?

There are 4 frequency bands in operation, low frequency (125KHz), high frequency (13.54MHz), ultra high frequency (850-910MFz), microwave (2.45GHz). Each frequency has its characteristics and is used in Different fields, so to use correctly, you must first choose the right frequency.

Do all countries use the same frequency?

No, UHF in Europe is 868MHz, and in the US it is 915MHz. Japan does not currently allow UHF to be used in RF technology. The government also limits its impact on other devices by adjusting the power supply to the reader. Some organizations, such as the Global Business Promotion Council, are encouraging governments to lift restrictions. Label and reader manufacturers are also developing systems that can use different frequency systems to avoid these problems.

How do we know which frequency is right for our product?

Different frequencies have different characteristics, so their uses are also diverse. For example, low-frequency tags are cheaper than UHF tags, save energy, and penetrate scrap metal objects. They are best suited for objects with high water content, such as fruits. UHF has a wide range of functions and transmits data quickly, but they are more energy-intensive, have less penetrating power, and do not have too much interference in the work area. They are suitable for monitoring items transported from the harbor to the warehouse. When making a choice, it is best to consult the relevant experts and suppliers to select the correct RF.

I have heard that radio frequency technology is not working properly with water or metal. Does it mean that it cannot be used to monitor canned or high water content?

no. The metal reflects the radio frequency and the water absorbs the radio frequency, so in this case the function of the tag is functioning properly. However, the designed system is very good at avoiding these problems.

What is a reader conflict?

One problem encountered with RF technology is the reader conflict, where the information received by one reader collides with the information received by another reader, creating an overlap. One way to solve this problem is to use TDMA technology, which is simply that the reader is commanded to receive signals at different times, rather than at the same time, thus ensuring that the readers do not interfere with each other. However, items in the same area will be read twice, so it is necessary to establish a system to avoid this.

How does a passive reader work?

RF readers transmit information in a variety of ways and tags. The reader uses the antenna to form a magnetic field around it. The passive tag receives energy from the magnetic field and sends the signal to the reader. The reader converts the information into electronic information—label electronics Product Code.

Can all readers support different kinds of labels?

Not yet. Many companies produce readers that support the RF technology of new tags used in existing supply chains. Some readers only support new electronic product codes, and some only support specific tags produced by some manufacturers.

What kind of reader do I need?

Like the tag, the reader has to decide the type and quantity of use by researching the supply method. For example, the requirement is to manage the inventory in and out of the warehouse, and the reader can be installed on the door of the terminal where the goods enter and exit. If the requirement is to manage the product for a particular customer, then the reader should be installed not only on the hatch, but also on the truck. If the requirement is to control the retail shelf, a fixed or handheld device can be used to facilitate automatic outbound logging and counting.