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Sensors in the IoT environment

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Industry 4.0 benefits are primarily driven by a data-driven strategy, the theory being that the more data you have, the better decisions can be made that positively affect your business. Data, in the traditional industrial sense, is driven mainly by automatic sensors that read “stuff” and is made available to a control system driven by PLCs and people. However, until recently, we have focused our efforts around the process we are trying to manage and not necessarily around other factors that might give us additional relevant data that may offer those incremental or significant improvements so necessary to drive efficiency in an ever more competitive world.

An example might be; is the operator spending the required time or taking the right breaks to ensure the highest quality monitoring of our industrial system? So monitoring humans is becoming very critical. I have yet to find a single customer that manages this.

If we work on that premise, then the new internet of things (IoT) world offers us tremendous opportunities to bring this new data into our environment. In order to make decent choices, we need to understand many factors that influence a decision, these include:

  • Technology: Does it fit into your technical and IT standards?
  • Fit for purpose: Does it meet your technical requirements?
  • Environment: Is the power required available on-site? How long is your battery backup?
  • Cost and contracts: Is there a complicated contract involved, what is the total cost of ownership (TCO)?

The IoT landscape

The IoT landscape is complex and forever changing as competitive forces jockey for position to become the network and chipset manufacturer of choice for the over 50-billion devices that are predicted to come into our lives over the next ten years. This article is not about which one is better than the other, each has advantages and disadvantages. This article is here to guide you in making your sensor choice which will ultimately influence your network choice. An industrial IoT solution will, in all likelihood, be made up of a combination of choices for both sensors and networks. In the end it doesn’t matter, it’s about getting to the solution that drives efficiencies and makes our human lives better and more comfortable.

The landscape is complex, but it forces one to ask the basic questions, and if you follow the basic questions, making decisions becomes easier.

What is the actual distance to the point of measurement?

Fig. 1 shows the distance supported and technologies within each zone. A general rule, though, is to assess how critical measurement is for the decision making. Is it just data to add to the data you already have, that can be used to better improve quality and cost? If it is critical, we are pretty much bound to the continuously powered, hard-wired sensor that is integrated into the PLC/DCS (comms could be wireless – usually some sort of WiFi standard so 8.02) where data is transmitted “instantaneously” for critical control decisions made in the control systems.

Fig. 1: The distance supported and technologies within each zone.

You can see from Fig. 1 that WiFi is rated and can be used up to 1000 m. Where you need to move into measurements in the 1 – 10 km range, it starts becoming interesting as we then start requiring decisions such as:

  • Do you install your own radio network?
  • Do you install a LoRa (long range) network?
  • Do you use the internet to act as the network?
    • LTE-M (long-term evolution)
    • NBIoT (narrow band internet of things)
    • GPRS (general packet radio services) running on GSM networks (mobile networks)
  • Do you leverage a dedicated IoT network such as Sigfox (0G Network)?

The issue, of course, is to balance the cost of deploying and maintaining your own network or leveraging the telco or IoT networks available where there is an ongoing cost of using that network.

Defining each network offering – Wikipedia

LTE-M (LTE-MTC [Machine Type Communication]), which includes eMTC (enhanced Machine Type Communication), is a type of low power wide area network (LPWAN) radio technology standard developed by 3GPP to enable a wide range of cellular devices and services (specifically, for machine-to-machine and IoT applications). Also see LTE Cat-M1.

NB-IoT is a LPWAN radio technology standard developed by 3GPP to enable a wide range of cellular devices and services. NB-IoT uses a subset of the LTE standard, but limits the bandwidth to a single narrow-band of 200 kHz.

LoRa is a long-range radio frequency technology (LoRa Technology) and is combined with low power wireless chipset that is used in a lot of IoT networks and devices worldwide. LoRa uses license-free sub-gigahertz radio frequency bands like 433 MHz, 868 MHz (Europe) and 915 MHz (North America). LoRa enables long-range transmissions (more than 10 km in rural areas) with low power consumption.

Sigfox employs the differential binary phase-shift keying (DBPSK) and the Gaussian frequency shift keying (GFSK) that enables communication using the Industrial, Scientific and Medical ISM radio band which uses 868 MHz in Europe and 902 MHz in the US. It utilises a wide-reaching signal that passes freely through solid objects, called “Ultra Narrowband” and requires little energy, being termed “low-power wide-area network (LPWAN)”.

Do you need to do control at the point of measurement?

If you need to do control at the point of measurement e.g. Switch a pump on and off based on a level or if the sensor you want to use requires permanent power, you will need power at the site. If either of these is true, you will need to put in some power infrastructure – solar, wind, generator or permanent power.

  • A PLC/RTU or some other controller needs permanent power.
  • A permanently powered sensor needs power.
  • You will also need some power infrastructure, if you choose either of the following, to send and/or receive data from the control point:
    • Radio.
    • Telecoms (modems, NBIot).
    • LoRa, if you are wanting to do control.

If you do not need control and simply want to be able to monitor and send the data back to the control point, then your decisions are about whether or not your sensor needs permanent power.

If you do not need to do control and your sensor does not need to be powered, then what choice of network do I have for my sensor?

If this is the case, then the decision needs to be made about how often you need data to be transmitted.

  • More than 140 messages a day, then your choice is to use self-powered sensors that leverage:
    • LoRa – need a dedicated network (in South Africa).
    • NBIoT – telco network.
  • Less than 140 messages a day, then your choice is to use self-powered, low power sensors that leverage:
    • Sigfox – choose a contract for 140, 75 or 2 messages a day.

Fig. 2: Different communication needs require different networks.

What infrastructure do you need for different IoT network technologies?

We are only dealing with wider area networks in this section.

  • WiFi requires WiFi points connected to a network or internet connection for backhauling the data from the sensors to the control point
  • LoRa requires private or a public LoRa network between the sensors at the control point.
  • NBIoT requires sensors that are built to support NBIoT.
  • Sigfox is granted and installed usually by a single network operator. In South Africa, the Sigfox network is handled by Sqwidnet (a division of Dark Fibre Africa).

Fig. 3: Network architecture to meet various needs.

Assuming I can use self-powered (battery) sensors, what choices do I have?

This is the interesting part. Many manufacturers of sensors allow and support various network offerings. The two big IoT networks that a lot of sensors support are LoRa and Sigfox and the internet is full of sensor offerings for either of these.

The one advantage of Sigfox, although limited to frequency and size of the message, is their sensor costs and availabilities, because of the homogeneous nature of the network and a certified sensor for a particular radio frequency licensed zone are compatible, and transportable. This means that any sensor purchased will work anywhere in the world where there is a Sigfox Network. The current sensor ecosystem for Sigfox compatible sensors comprises of over 750 products from almost 700 companies.

A huge advantage is cost, where most basic sensors cost less than R1500. Even more complex sensors like the Adroit pressure sensor can be easily deployed and integrated into the Adroit SCADA system and costs around R7500 compared to a fixed installation using standard telemetry of around R35 000 to R50 000.

In addition, we have undertaken to create an ObjectModel for any customers Sigfox sensor, free of charge, into the Adroit IoT/SCADA platform.

Conclusion

The time has never been riper to enhance your business using IIoT; sensor and network choice usually comes out in the wash. These IoT networks and sensors are reliable, cheap and can deliver massive value if deployed and used within a larger digital strategy.

Contact Dave Wibberly, Adroit Technologies, Tel 011 658-8100, info@adroit.co.za 

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