rfid faq

Is RF signal harmful for human beings and the environment?
No. The power levels used for any RFID applications are well below the power levels that prove to have any harmful effects. RFID uses the low-end of the electromagnetic spectrum and is in compliance with the Federal Communications Commission(FCC) regulation.
Does RF signal pass through walls?
RF signals easily pass through walls. Tags can also be read through a variety of substances such as snow, fog, ice, paint, grease, oil, etc. and other visually and environmentally challenging conditions, where barcodes or other optically read technologies would be useless. The signal strength of RF falls off inversely to the distance travelled and is further degrade by passing through walls or reflecting off metal fixtures.
How does an Passive RFID system work?
The RFID system consists of an tag, which consists of a microch ip with a coiled antenna, and an interrogator/reader with an antenna. The reader emits electromagnetic waves that form a magnetic field when they “couple” with the antenna on the RFID tag. A passive RFID tag powers the microchip’s circuits by drawing the power from this magnetic field. The microchip then modulates the waves that the tag sends back to the reader and the reader converts the new waves into digital data.
Is RFID better than using bar codes?
The two are different technologies which have some common applications. The biggest distinguishing factor between the two is bar codes are line-of-sight technology which require the bar code to be oriented towards the scanner for it to read.Radio frequency identification doesn’t require line of sight. RFID tags can be read as long as they are within range of a reader. Bar codes have several other shortcomings as well. If a label is ripped, soiled or falls off, there is no way to scan the item.Standard bar codes can identify only the manufacturer and product, they donot have a unique ID. The bar code on one medicine bottle is the same as every other, making it highly impossible to identify which one reaches its expiration date first.
Will RFID replace bar codes?
No. RFID and bar codes will have to coexist.
How much does an RFID tag cost?
The Passive tags cost a magnitude less than Active tags. The Passive tags can cost as little as 30 cents or even less if bought in bulk Active tags – those with a battery – can cost far more. Some Active tags even come with temperature or pressure sensors built in, which cost more than $100.
Does RFID work around metal and water?
Radio waves cannot pass through metal,it bounces off metal and are absorbed by water at higher frequencies. This makes tracking metal products or those with high water content difficult, but with a good system design and engineering these problems can be easily overcomed.
What is the difference between passive, semi-passive and active tags?
Active RFID tags have a battery, which is used to run the microchip’s circuitry and to transmit a signal to a reader. Passive tags have no battery. They draw power from the reader, which sends out electromagnetic waves that induce a current in the tag’s antenna. Semi-passive tags use a battery to run the chip’s circuitry, but communicate by drawing power from the reader. Active and semi-passive tags are useful for tracking /location of high-value goods that need to be scanned over long ranges, but they are costly, making them very expensive to put on low-cost items. The read range for Passive tags is less than ten feet. In case of Active tags the read range is 100 feet or more. Passive tags are far less expensive than active tags and require no maintenance.
How much data can be stored in a tag?
It depends on the vendor and the application, but typically a tag would store around 2KB of data which is good enough to store some basic information about the item it is on.
What is the difference between read-only and read/write tags?
Microchips in RF tags can be read-write or read-only. With read-write chips, information can be added to the tag or write over existing information when the tag is within range of a reader/interrogator. Since the Read-write tags are expensive they are used only in some specialized applications. Some read-only microchips have information stored on them during the manufacturing process. The information on such chips can never been changed. With a EEPROM(electrically erasable programmable read-only memory) the data can be overwritten using a special electronic process.
How does tag collision occur?
Tag collision occurs when more than one tag sends back a signal at the same time, confusing the reader. Different vendors have developed different systems for having the tags respond to the reader one at a time.
What are the different read ranges for a typical RFID tag?
The read range for a passive tag depends on a lot of factors i.e the frequency of operation, the power of the reader, interference from metal objects or other RF devices. In general, low-frequency tags are read from a foot or less. High frequency tags are read from about three feet and UHF tags are read from 10 to 20 feet. Where longer ranges are needed, active tags are used to boost read ranges to 300 feet or more.
Are there any standards for RFID?
Yes. There are number of standards that define the various aspects of operation of the RFID Technology.Some of them are:The Auto-ID standard set up by Uniform Code Council(UCC) and EAN International, and promoted by the Auto-ID consortium.At present, the UCC standards offer the most compatible technology for RFID systems, and are the de-facto standards for all commercial implementations