What is RFID?
RFID (Radio-Frequency Identification) is a technology in which a reader uses radio waves to wirelessly read the unique identity and any stored data of an RFID tag: a small label with a chip and an antenna attached to an object, product, carrier or person. Unlike a barcode, no line of sight is needed, and one reader can register dozens or even hundreds of tags at once. RFID is used in logistics, manufacturing, retail, healthcare and access control, and in factories it often forms the bridge between the physical product and systems such as MES, WMS and ERP.
🧠 How does RFID work?
An RFID system consists of four parts:
- RFID tag (transponder) - a chip with a unique ID and sometimes extra memory, connected to an antenna. The tag sits in a label, card, key fob, screw-in housing or glass capsule.
- Reader antenna - generates the radio field that addresses the tag and, for passive tags, powers it.
- RFID reader - sends commands to the tag, captures the response and decodes it. A reader with several antennas can cover an entire dock door or conveyor.
- Middleware and back end - filters duplicate reads, links the ID to an object and passes the event on to, for example, a PLC, MES or WMS.
At LF and HF the coupling is inductive: reader and tag behave like the two coils of a transformer, which limits the range to centimetres or at most about one metre. At UHF the tag uses backscatter: it reflects part of the reader’s radio signal and modulates its answer onto it. That gives a range of metres. An anti-collision protocol keeps tags from talking over each other, so a full pallet can be counted in a single pass.
🏷️ What is an RFID tag and which types exist?
An RFID tag is the carrier of the identity: a microchip for storage and processing plus an antenna for communicating with the reader. By power source there are three types:
| Tag type | Power | Typical range | Characteristics |
|---|---|---|---|
| Passive | Draws energy from the reader’s field | Centimetres (LF/HF) to several metres (UHF) | Cheap, maintenance-free, usable for years; by far the most common form |
| Semi-passive (battery-assisted passive) | Battery powers chip and sensors, communication via backscatter | Longer than passive | Suited to sensors, for example temperature logging in the cold chain |
| Active | Own battery and transmitter | Tens of metres to a hundred metres or more | More expensive, battery needs replacing; for containers, vehicles and large assets |
The memory of a UHF tag following the EPC Gen2 standard is divided into four memory banks: Reserved (kill and access passwords), EPC (the object’s identification code), TID (a chip ID fixed by the manufacturer) and an optional User bank (free memory). Sizes vary per chip; one chip has 512 bits of user memory, another has none at all. Industrial HF tags can hold several kilobytes, for instance FRAM memory that can be written quickly and often.
Note the difference with a tag in SCADA or a PLC: that is a named process variable in software, not a physical label.
📡 Which RFID frequencies are there?
| Band | Frequency | Range (passive) | Key standards | Applications |
|---|---|---|---|---|
| LF | 125–134.2 kHz | Up to approx. 10 cm | ISO 11784/11785 (animals), EM4100 cards | Animal ID, simple access badges, immobilisers |
| HF | 13.56 MHz | Up to approx. 10 cm (ISO 14443) or approx. 1 m (ISO 15693) | ISO 14443, ISO 15693, NFC (ISO 18092) | Payment and transit cards, libraries, tool identification |
| UHF | 865–868 MHz (EU), 902–928 MHz (US) | Several metres, approx. 10 m in favourable conditions | EPC Gen2 = ISO/IEC 18000-63, ETSI EN 302 208 | Pallets, clothing, stock counts, gate detection |
| Active | e.g. 433 MHz and 2.45 GHz | Up to 100 m or more | e.g. ISO/IEC 18000-7 | Vehicle and container tracking, outdoor yards |
In Europe, ETSI EN 302 208 governs use of the 865–868 MHz UHF band at up to 2 W ERP. Readers and tags for the US use a different band, so for international supply chains you choose tags that support both. Passive UHF is also marketed as RAIN RFID.
🏭 What is RFID used for in industry and logistics?
| Application | How RFID is used |
|---|---|
| Product carriers in assembly | An HF tag on each carrier tells the station which product and variant is arriving; the MES sends the right recipe |
| Tool identification | A tag in the tool holder stores ID, dimensions and tool life; the machine reads it at every tool change |
| WMS and logistics | A UHF gate registers every case on a pallet at receipt and dispatch, linked to the SSCC |
| Inventory management | Handheld readers count an entire warehouse or shop shelf in minutes |
| Retail and apparel | A tag on each garment enables fast stock counts, replenishment and theft detection at the exit |
| Tracking and Tracing | Every process step is recorded with a timestamp for traceability and recalls |
| Healthcare | Tags on medical devices support registration and locating equipment alongside UDI codes |
| Asset Management | Moulds, roll cages and measuring instruments stay traceable in the asset inventory |
| TMS and transport | Automatic recognition of vehicles or load carriers at docks and gates |
📦 What is the difference between RFID and a barcode?
| Aspect | RFID | Barcode (EAN-13, GS1-128, QR Code) |
|---|---|---|
| Line of sight needed? | No, the tag can sit inside the packaging | Yes, the code must be visible to the scanner |
| Read range | Centimetres (LF/HF) to metres (UHF) | A few centimetres to several metres, depending on scanner and code size |
| Several at once? | Yes, bulk reading through anti-collision | No, one code per scan |
| Writable? | Many tags are (EPC and user memory) | No, the content is fixed when printed |
| Cost per label | Higher: chip and antenna | Very low: printable |
| Sensitive to | Metal and liquid (UHF in particular) | Dirt, damage and poor print quality |
Because RFID reads automatically and in bulk, it gives real-time visibility of stock and location with fewer manual errors, which supports process automation in the warehouse and factory. RFID rarely replaces all barcodes. In the GS1 world the same identity can be held in a barcode, a DataMatrix and an EPC tag: the GS1 EPC Tag Data Standard describes how, for example, a product number with a serial number is encoded in the EPC bank.
🔧 How do you integrate RFID into an OT environment?
Industrial RFID readers speak the language of automation. Common connections are:
- IO-Link - simple HF readers deliver the tag ID as process data through an IO-Link master. No RFID-specific programming in the PLC is needed.
- ProfiNET and Ethernet IP - more capable readers are fieldbus devices in their own right, with function blocks for reading and writing tag memory.
- OPC UA - the companion specification OPC UA for AutoID Devices defines a uniform information model for RFID readers, barcode scanners and similar identification devices.
- MQTT or REST - UHF readers in warehouses often send read events straight to middleware, an edge platform or a Unified Namespace.
A practical step-by-step plan for an RFID project:
- Define the goal and read distance - one carrier at 30 mm calls for HF, a pallet in a dock door for UHF.
- Test on the real material - metal reflects and liquid absorbs UHF energy, which can make an ordinary label unreadable. Use on-metal tags with a spacer, or choose HF.
- Decide the data structure - only an ID on the tag with everything else in the database, or data on the tag itself (useful when the connection to the back end drops).
- Design reader placement and filtering - stop a reader picking up tags from an adjacent lane.
- Connect to existing systems - decide which system owns the event: PLC, MES or WMS.
🔐 How secure is RFID?
RFID was designed for identification, not automatically for security. The main risks:
- Cloning - many 125 kHz cards of the EM4100 type repeatedly transmit the same fixed 64-bit code (containing a 40-bit unique number) with no encryption or authentication at all. With cheap hardware such a badge can be copied in seconds. Never use LF badges as the only factor for access to control rooms or server rooms.
- Broken cryptography - in March 2008 researchers at Radboud University Nijmegen found a flaw in MIFARE Classic, the chip used in, among others, the Dutch OV-chipkaart transit card. Manufacturer NXP tried to stop publication through summary proceedings, but the court in Arnhem allowed it. Modern cards use stronger cryptography such as AES.
- Spoofing and tampering - writable tags without an access password can be overwritten, feeding a production process the wrong data. EPC Gen2v2 (2013) added optional cryptographic authentication and an untraceable feature.
- The network side - a reader is a network device with firmware and a web interface. Place readers in the right zone following network segmentation and manage them like any other OT component.
- Privacy - tags that can be linked to people fall under the GDPR (in Dutch, AVG). In Recommendation 2009/387/EC the European Commission advised carrying out a privacy impact assessment before deployment; EN 16571 describes that process and EN 16570 the information sign and the details you give to the people concerned. Apply privacy by design, for example by deactivating tags at the checkout.
❓ Frequently asked questions
What is the difference between RFID and an RFID tag?
RFID is the technology as a whole: reader, antenna, tag and software that identify objects via radio waves. An RFID tag is only the label with chip and antenna that sits on the object. Without a reader and back end, an RFID tag does nothing.
What is the difference between RFID and NFC?
NFC is a form of HF RFID at 13.56 MHz with a very short range of a few centimetres, based on ISO 14443 and ISO 18092. NFC also supports two-way communication between two devices, such as a phone and a payment terminal. RFID in general also covers LF and UHF, with ranges of several metres.
How far can an RFID reader read a tag?
The range of RFID depends on frequency, tag type and environment. LF and HF usually reach no further than 10 cm to about 1 m, passive UHF reaches several metres and around 10 m in favourable conditions. Active RFID tags with their own battery reach 100 m or more.
Does RFID work on metal and near liquids?
Ordinary UHF RFID tags perform poorly on metal and near liquids, because metal detunes the antenna and water absorbs the radio energy. Special on-metal tags with a spacer layer solve this. HF RFID is also less sensitive and is therefore often chosen for metal tools and product carriers.
Is RFID more expensive than a barcode?
An RFID tag costs more than a printed barcode, and readers and integration require a larger investment. In return, RFID reads without line of sight and in bulk, which cuts manual work and counting errors. Whether RFID pays off depends on the number of read points and the value of real-time visibility.
Can an RFID badge be copied?
Simple 125 kHz RFID badges without encryption can be copied with cheap equipment. Cards with modern cryptography, such as AES-based HF cards, are much harder to clone. Combine RFID access to critical OT rooms with a PIN or a second factor.
📌 In summary
RFID identifies objects wirelessly through an RFID tag and a reader. The choice between LF, HF and UHF determines range, speed and sensitivity to metal and liquid. In the factory, RFID links the physical product to MES and WMS via IO-Link, PROFINET or OPC UA; across the supply chain it enables tracking and tracing and fast stock counts. Security and privacy belong in the design from day one.
RFID makes objects recognisable automatically and without line of sight, but it only delivers value with the right frequency, properly tested tags and a secure connection to OT and IT systems.