Wireless Sensor Basics and Types

This page covers the basics of wireless sensors and discusses different wireless sensor types. It includes information on NFC, RFID, Bluetooth, and Zigbee-based wireless sensors.

Wireless sensors typically consist of two main parts: a transmitter and a receiver.

• The transmitter converts signals from process control instruments into a wireless radio transmission.
• The receiver converts the wireless signal into a specific desired output, such as an analog current or data.

As wireless standards continue to evolve, wireless sensors are becoming available for a wider range of applications.

Common types of wireless sensors include:

• NFC sensors
• RFID sensors
• Bluetooth sensors
• Zigbee-based sensors

Wireless Sensor Types

NFC Sensor

NFC (Near Field Communication) is a short-range wireless communication technology where the antenna size is smaller than the operating wavelength. It operates using either the electric field (E-field) or the magnetic field (H-field) and does not support electromagnetic (EM) waves.

In mobile phones, NFC technology typically uses the E-field and operates at a frequency of 13.56 MHz, with a wavelength of 22.11 meters.

NFC sensor-based devices are commonly used at ticket counters and for car parking systems.

RFID Sensor

RFID (Radio-Frequency Identification) sensors consist of a small antenna and a small chip. This technology is used to track items over a distance and is suitable for low byte data transfer.

An RFID system comprises tags attached to items and readers. The readers transmit RF waves and receive the reflected waves from the tags to determine the distance and other parameters.

RFID is used in applications like barcodes or magnetic strips on credit cards or debit/ATM cards, serving as a unique identifier.

Bluetooth Sensor

Bluetooth wireless sensors use the UHF band within the ISM (Industrial, Scientific, and Medical) frequency band. It is used to exchange data over shorter distances.

There are various classes of Bluetooth devices based on their range and power levels.

Zigbee Sensor

Zigbee wireless sensors are based on the Zigbee standard (IEEE 802.15.4). These high-level communication protocols are used to create Personal Area Networks (PANs).

Zigbee devices are low-power and typically cover distances from 10-100 meters in line-of-sight (LOS) scenarios. Zigbee routing protocols have been developed to facilitate long-distance transmission with the help of mesh network topologies.

A Zigbee network is composed of end devices, routers, and a coordinator.