Wireless Sensors for Monitoring IoT Connected Building Applications

Connectivity and Internet of Things (IoT) and Industrial Internet of Things (IIoT) are changing how organisations and businesses remotely monitor applications and areas within their buildings. Wireless sensors provide a low-cost way to deploy sensors rapidly and easily for a wide range of environmental factors to allow data to be collected for monitoring, analysis, reporting, alerts and where necessary, corrective, or preventative actions.

Wireless sensors can provide the information necessary for the automation and control of building management systems and processes including heating, ventilation, and control (HVAC), occupancy measurement and energy saving programs. The sensors can also be used to control smart grids and enable a move towards carbonless fuelled economies.

For a wireless sensor to report its data, requires an IoT wireless gateway.

What is a IoT Wireless Gateway?

When designing a wireless monitoring system, it is important to determine what you want to gather data on and to choose the correct sensors. Each environment monitoring system manufacturer offering IoT wireless sensors will also have a wireless gateway as part of their eco-system.

A wireless IoT Gateway is a centralised hub that connects wireless IoT sensors and devices to a cloud-based monitoring platform for data processing and analysis. The monitoring platform will typically provide a dashboard overview and allow authorised users to setup sensor ranges, alerts via email and SMS text messages and reports. Some IoT gateways allow directional data flow and automation logic functions.

The wireless gateway provides the sensors with an internet connection via a local WiFi wireless access point (WAP) or built-in 4G modem using an IoT communications technique such as LoRa. The gateway provides access and bandwidth to allow multiple IoT sensors to report their data and may include firewall capabilities.

A typical wireless gateway is the Smart Data 4G Cloud connector. This is part of the Disruptive Technologies range which also includes wireless sensor tiles. The tiles can be up to 25m from the gateway, can have a 15year battery life and are simply attached to any surface using an adhesive backing. The tiles are extremely small, measuring 19×19×2.5mm.

The 4G cloud connector relays data to a Cloud service using SecureDataShot™ technology via Ethernet or a 4G/LTE cellular connection. The gateway connector is ‘plug and play’ and does not require configuration during installation. A built-in SIM card means that the Cloud Connector can always connect to its monitoring platform and roams freely between the best mobile networks in the area. SecureDataShot™ is a proprietary Sub-1GHz wireless communication protocol, made specifically for creating a scalable network of sensors, maintaining security while using as little energy as possible.

Another approach to wireless gateways comes in the form of the AKCP sensorProbe Wireless Tunnel. The AKCP sensorprobe wireless tunnel can monitor up to 4x ACKP plug-in sensors using LoRa wireless communications over long distances up to 3km (over 1.5miles). AKCP’s proprietary Wireless Tunnel protocol provides guaranteed message delivery without loss of data and with low power utilization to help extend battery life. Data is transmitted to the sensorProbe Wireless Tunnel Server (SP-WTS). Multiple units can be monitored centrally with AKCPro Server, which can run locally or as a Cloud-base software platform.

The sensorProbe+ Wireless Tunnel is equipped with Semtech’s LoRa based radio technology and the AKCP Wireless Tunnel communications protocol. Up to four times wired intelligent sensors can be connected to a single SP-WT device. Up to 30x SP-WT devices can be connected to the sensorProbe+ Wireless Tunnel Server (SP-WTS), allowing up to 120 intelligent sensors to be monitored.

For more information on the wider research being carried out in relation to WiFi-based Wireless Sensor Networks (WSN) and their usage in IoT, smart grids, smart agriculture and intelligent envrionment protection, see: https://ieeexplore.ieee.org/abstract/document/5975693

Types of Wireless IoT Sensors

Each environmental monitoring system manufacturer will provide a range of sensors as part of their wireless monitoring solution. This allows multiple sensors to be installed for a range of environmental factors requiring monitoring. Typical examples include:

• Temperature
• Humidity
• Occupancy levels
• Motion
• Air Pressure
• Air Quality, CO2 and Volatile Organic Compounds (VoC)
• Level sensors
• Image sensors
• Proximity sensors
• Water detection sensors
• Water leakage sensors
• Touch detection sensors
• Chemical sensors
• Gas sensors
• Smoke sensors
• Infrared (IR) sensors
• Acceleration sensors
• Optical sensors

Some of these sensors are often used within computer and server rooms and data centre applications. Examples include temperature and humidity monitoring, water leakage monitoring and security aspects including motion detection. From a wider intelligent building point of view, room occupancy levels have become important as organisations strive to improve their energy efficiency and adopt hybrid working. Air quality can also be important as part of wellbeing initiatives.

Wireless Sensors for Server Rooms and Data Centres

Wireless sensors can be easily deployed in an IT environment without the additional costs of network cabling and connection points, provided there is a suitable wireless gateway and/or WiFi connectivity. The most installed wireless monitoring sensors to monitor IT facilities include:

• Temperature
• Humidity
• Water leakage
• Motion
• AC power presence with reboot
• Generator fuel levels

Additional sensors can include smoke and fire detection but often this is aspect is covered by a fire alarm system and is installed with a supporting fire suppression system.

Wireless Temperature Sensors

The ideal temperature range for a server room or data centre is 18-25°C. A wireless temperature sensor can be installed at a single point in an IT room and most often it is installed, connected to the top/side of a central server rack. In larger rooms, multiple temperature sensors may be installed. For high-end computing applications, multiple sensors may be connected in each server cabinet, and this can be up to six sensors to cover the front and back, top, middle, and bottom of the cabinets. This approach helps to identify hot spots within the server cabinet.

Wireless Humidity Sensors

The ideal humidity range for a server room or data centre is 40-60% relative humidity. Too low a humidity level can lead to a build up of static electricity. Too high a humidity can cause corrosion and moisture collection which can lead to a short-circuit and fire risk potential. Measuring how much water vapour is a server room can help to detect if there is an issue with the local air conditioning and HVAC system. An issue being a potential fault or incorrect setting.

Wireless Water Leakage Sensors

Water or any other conductive liquid presence around electrical and electronics circuits is a ‘no-no’. Water leakage in a server room or data centre can occur if there is a poorly performing air conditioning, dripping condensate/moisture onto a pool underneath or from a cracked HVAC or water pipe. Spot water sensors can detect water or liquid presence in a particular spot. Water leakage ropes can detect water or liquid presence along a length of sensor report and report its position through the wireless gateway.

Wireless Motion Sensors

Entry into any computer, server room or data centre should be access controlled. That is under the control of an access control system and requiring presentation of a secure credential to gain entry to the IT space. A credential can be in the form of an access control card, mobile phone credential or even a biometric facial recognition or finger-print reader.

Wireless motion detectors monitor for motion within a physical space and can be important if there is no access control system in place or as a double-check on an authorised entry. Motion detectors cam use passive infrared (PIR), microwave or ultrasonic detection technologies. For some IP cameras, motion detection is built-into the device. Where this is not possible a wireless motion sensor can be easily deployed.
h3. Wireless AC Voltage Presence

AC voltage sensors detect the presence or absence of an input AC (alternating current) power supply, mains power, uninterruptible power supply or generator. Whilst a UPS system and generator will incorporate remote monitoring via dry-signal contacts and SNMP, the addition of a wireless AC voltage sensor can provide a double-check on the supplies available. DC version of the sensor are also available to monitor for the presence or absence of a battery or rectifier supplied direct current (DC).

Wireless Generator Fuel Level Sensors

Wireless fuel level sensors play a vital role in when server rooms and data centres must rely on backup power from a standby power generator. Normally the runtime available from the uninterruptible power supply is only around 10-30minutes. Enough time for a generator to start-up and get to full load power; normally around 1-2 minutes. The extra battery runtime is there just in case the generator does not auto-start.

Generators are not only used to provide backup power to UPS systems and their protected loads. A generator will normally be sized to cover essential services including lighting and other data centre building managing systems including security, CCTV and HVAC systems.

A typical day tank on a generator will provide from 8-12hours of standby power. Provided there is enough fuel. Wireless fuel level sensors provide continuous fuel level readings. The sensors provide an additional layer of security to a business continuity plan and can prevent fuel tanks from going to dangerously low levels.

General Building System Wireless Sensors

Environmental monitoring can be used in a wide range of building applications including server rooms and data centres. Examples include cold-chain storage, food distribution, warehousing, industrial manufacturing plants and buildings who want to be more in control of their energy efficiency and environmental impact.

Wireless Air Quality Sensors

Wireless air quality sensors always been important to industrial site operators. In recent years, the sensors can contribute important data for employee and visitor wellbeing programs. Sensor usage has also increased following COVID-19 and the need to ensure adequate air flow and quality.

Air quality sensors can monitor for the presence of air particles that could be damaging including Volatile Organic Compounds (VoC), Metal Oxide Gasses (MOx), temperature and humidity, and Carbon Dioxide (CO2) levels.

Wireless Motion Passive Infrared (PIR) Sensors

All physical objects can generate infrared radiation which can be detected using infrared sensors. A typical example being contactless thermometers that can be used to measure nearby temperatures. Typical server room and data centre applications including temperature monitoring if IT hardware, server cabinets, air conditioning systems and electrical switchgear.

Wireless Room Occupancy Management Sensors

PIR sensors can also be used to measure room occupancy usage and levels. When motion is detected, a time can start to measure how long people are within a monitored area. The data gather from a room occupancy level sensor can impact a variety of building usage related programs including energy saving, routine cleaning and general maintenance and refurbishment.

Wireless Proximity Sensors

Proximity sensors can be used throughout a building for example to detect whether people are present or not. A typical example is a security system with a PIR (passive infra-red) sensor. There are distinct types of proximity sensor including inductive technology-type sensors that can be used to detect for metal objects, capacitive that monitor for different dielectric constants, photoelectric which used reflected light and ultrasonic that use sound-based signals.

Wireless Chemical Sensors

Using chemical sensors can help to quickly identify leaks that could be harmful to workers, the general population, and surrounding areas. This can be important on industrial manufacturing and storage sites for example.

Wireless Gas Sensors

Gas sensors can be used to monitor and detect for various gas types including combustible, poisonous and flammable. Typical gasses monitored include Acetone (used in paints and glues), Toluene (used in furniture), Ethanol (used in perfumes and cleaning fluids), Hydrogen Sulphide (present in decaying food stuffs) and Benzene (present in cigarette smoke).

Wireless Image Sensors

Image sensors collect data via digital pictures. Automatic number plate recognition (ANPR) cameras are common examples. Others including facial recognition cameras. Wireless image sensors can play a role on manufacturing sites capturing images of products on automated production lines that can be used to measure production effectiveness i.e., a surface coating.

Wireless Optical Sensors

Optical sensors can measure the light reflected from an object and be used to detect an interruption in a beam of light or a reflection caused by the movement of an object into the field of view. Typical optical sensor examples including through-beam sensors, retro-reflective sensors, and diffuse-reflection sensors.

Through-beam Sensors detect objects by the interruption of a light beam as the object crosses the path between a transmitter and remote receiver. Retro-reflective sensors combine a transmitter and a receiver into a single unit and use a separate reflective surface to bounce the light back to the device. Diffuse-reflection Sensors operate in a comparable way to retro-reflective type sensors but the object being detected serves as the reflective surface.

Wireless Pressure Sensors

Pressurised systems that store air, gas or liquids require a certain level of pressure to operate safely. Wireless pressure sensors measure the force per unit of pressure applied on to the sensor and allow alarms to be automatically generated when pressure readings drop or rise above pre-set thresholds.

Wireless Acceleration Sensors

Acceleration sensors measure how quickly an object changes its velocity, even from a zero state. Vibration and rotation can also be monitored for using Hall-effect, capacitive and Piezoelectric sensors.

Wireless Water Quality Sensors

Water quality is vital to life and many other processes. Water quality sensors can monitor water supplies for the presence of chemicals including chlorine and fluoride, measure oxygen levels, electrical conductivity (ion levels), PH levels (acid or alkaline) and even turbidity levels which measures the number of suspended solids in water.

Summary

Wireless sensors provide a way to easily install sensors around and within a building. Their deployment can be low cost if there is a suitable and cybersecure gateway and/or Wi-Fi network in place. Cabling and connectivity costs are dramatically reduced, and additional sensors can be added easily.

Sensor deployment is only one aspect of a secure and reliable environmental monitoring solution. Alerts, triggers, and actions must be configured and regularly tested to ensure that the monitoring system is providing the information and actions originally intended. This can include SNMP polling and the automatic generation of email and SMS text alerts and even phone calls to predefined user groups. This should form part of an annual business continuity review and even a simulated power or cooling system failure onsite.