What is RFID

An RFID system has three parts: a tag, a reader with one or more antennas, and software that decides what the reads mean.

A passive tag has no battery. The reader transmits radio energy through its antenna, the tag harvests that energy, wakes up, and transmits its number back. This is why passive tags last for decades and cost a few rupees — there is nothing in them to wear out.

An active tag has a battery and transmits on its own. That gives far greater range, tens of metres rather than a few, at a much higher cost per tag and with a battery to replace every few years.

Because the exchange is radio rather than optical, nothing has to be seen. A tag reads inside a carton, through shrink wrap, in a pocket and on the far side of a stack. That single property is what makes RFID different from barcode, and it is the reason a carton can be verified without opening it.

LF, 125 kHz. A few centimetres of range. Tolerates metal and water better than the others. Slow, one tag at a time. Used in older access cards, animal microchips and industrial environments where nothing else survives.

HF and NFC, 13.56 MHz. Up to about ten centimetres, one tag at a time. Every modern smartphone can read NFC, which makes it the choice when a person deliberately taps something — access cards, transit, tap-to-pay, product authentication.

UHF, 865–867 MHz in India. Several metres of range and hundreds of tags per second. This is the band for counting things without handling them: warehouse pallets, retail stock, jewellery trays, linen trolleys, library shelves.

2.45 GHz active. Tens of metres, battery powered. Used for vehicles, containers and high-value assets where the tag cost is small against the item.

The Indian UHF allocation is 865 to 867 MHz. Readers sold for other markets may be configured for 902 to 928 MHz, which is not permitted here. Check this before buying imported hardware.

Passive tags cost from a few rupees, have no battery, last as long as the item they are attached to, and read from a few centimetres to about ten metres depending on the band and the antenna. They are the right answer for almost everything.

Active tags cost hundreds of rupees each, contain a battery good for three to five years, and read from thirty to a hundred metres. They are the right answer when you need to locate something in a large open area — a vehicle in a yard, a container in a stack — and the item is valuable enough to justify the cost.

Battery-assisted passive tags sit between the two: a battery powers the chip but the reply still uses the reader's energy, giving longer range than passive at a lower cost than active.

Most projects that think they need active tags actually need better antenna placement.

Five questions decide the tag:

What is the surface? Metal detunes a tag and stops it working. On-metal tags have a ferrite layer that solves this. Liquid absorbs UHF energy, so a tag on a full bottle behaves differently from one on an empty bottle.

What is the environment? Industrial wash, high temperature, outdoor UV, chemicals and freezer storage all need specific tag constructions. A paper label will not survive a laundry.

What range do you need? Range comes from tag antenna size as much as from reader power. A small jewellery tag will never read at eight metres, and it does not need to.

How is it attached? Adhesive, sewn in, moulded in, riveted, cable-tied or hung. This often narrows the choice more than the electronics do.

How long must it last? A shipping label lasts a week. An asset tag lasts a decade. A laundry tag has to survive 200 wash cycles.

Then test. Take two or three candidates, read them on your actual item in the actual orientation, and measure. This is the single most valuable day in an RFID project.

Fixed readers are mounted where things pass and read continuously without anyone doing anything. Use them at dock doors, gates, conveyors and shelves — anywhere the counting must happen whether staff remember or not.

Handheld readers are rugged Android devices with a UHF reader inside. Use them for counting a room, auditing a yard, or finding one specific item. They are also how you cover the ninety per cent of a site where a fixed reader will never be justified.

Antennas matter more than the reader. Gain, polarisation, beam width and mounting angle decide what actually gets read. Circular polarisation reads tags at any orientation, which suits mixed goods. Linear reads further but only when the tag is aligned, which suits a controlled conveyor.

Ports and power. A four-port reader driving four antennas covers a standard dock door. More ports let one reader cover several doors, which is often cheaper than several readers.

Read rate is an installation property, not a product property. The same reader will give 92% or 99.9% depending on tags, antennas, placement and tuning. Buy the commissioning, not just the box.

Barcode is cheaper per item — effectively free if you are already printing a label. It needs line of sight, it reads one item at a time, and a scratched or dirty code does not read at all.

RFID costs a few rupees per tag. It needs no line of sight, reads hundreds of items at once, works through packaging, and survives dirt.

The decision is not ideological. Use RFID where reading many items at once, or reading without handling, saves real time — warehouse receipt, stock counting, asset audit, linen, jewellery, libraries. Use barcode where items are handled individually anyway — a retail counter, a pharmacy sale, a laboratory tube.

Most real deployments use both, and there is nothing wrong with that. Our software accepts RFID reads and barcode scans in the same flow, so a site can choose per item type rather than per system.