Sensors for the Development of the IoT – The 5th Industrial Revolution

By Cyril Robinson Azariah JJun 8 2018

We are at the start of the 5^th industrial revolution, known as the “Internet of Things” (IoT). IoT is the rise of the architecturally connected objects, which will rival past technological prodigies, such as the printing press, the steam engine, electricity, and computers. This decade of innovative technology is dedicated to recent advances in the field of sensors, interfaces, and references, intended for use in wearable and IoT applications. The contribution of sensors to the mobile communication is enormous.

Image credit: Panchenko Vladimir/Shutterstock

As these applications are usually battery powered, the crucial requirement needed is for high energy efficiency. This efficiency can then be united with competitive duty cycling to reach extremely low (nW) levels of average power. A few of the sensors for the development of IoT, contributed by various researchers across the globe, are discussed here:

1. Nick van Helleputte et al. from IMEC, Belgium, discusses progressions in the design of analog circuits envisioned for use in wearable healthcare applications. The various general trends toward multimodal sensing were examined in his work. Circuit topologies for the highest applicable sensing modalities, e.g., ExG, bio-impedance, and photoplethysmogram (PPG), were presented along with the recent state-of-the-art implementations.
    
2. Rajesh Pamula, Chris van Hoof, and Marian Verhelst, from IMEC, Belgium, carried out innovative work of an ultra-low power PPG readout circuit that exploits various mixed signal processing techniques. In particular, the use of compressive sampling (CS) allows the power consumption of its LED driver to be reduced by 30x. In the compressed domain, the heart rate information is then extracted by dodging the use of complex signal reconstruction techniques.
    
3. David Ruffieux and his team from Swiss Center for Electronics and Microtechnology, Switzerland, in their recent research define an ultra-low power (240 nA) real-time clock module that realizes a characteristic accuracy of ±1 ppm at 1 Hz over the industrial temperature range (40–85 ^oC). It syndicates a tiny 32 kHz quartz crystal and an ASIC in a mini 8-pin ceramic package. An all-digital interpolation structure permits its 1 Hz output to be pared with a resolution of 0.1 ppm, resulting in significant savings in both circuit area and power consumption.
    
4. Sining Pan and Kofi Makinwa from the electronic instrumentation laboratory, Delft University of Technology, The Netherlands, in their recent innovative research on sensors presented two resistor-based CMOS temperature sensors. Dr. Pan and his team’s first case is a Wien bridge RC filter, which has a temperature-dependent phase shift; while the other is using a Wheatstone bridge, which yields a temperature-dependent current. In both cases, continuous-time delta-sigma modulators digitize the bridge outputs. This provides a state-of-the-art energy efficiency and the low power dissipation (<200 µW).
    
5. Javier Perez Sanjurjo and his team from the electronic technology department, Carlos III University, Madrid, Spain, provided an integrating dual-slope (DS) capacitance-to-digital converter (CDC). This is accustomed to digitize the output of a pressure-sensing capacitive Wheatstone bridge. The planned CDC creates a multi-bit output with the help of time domain instead of amplitude domain methods. It also produces quantization noise shaping to reduce measurement time. The CDC achieves a capacitive sensing resolution of 5.4 aF (17-bits) while consuming only 146 µA from a 1.5 V power supply.
    
6. Shikhar Tewari and Aatmesh Shrivastava, US Boston North-eastern University Scientists, presented a 48 nW bandgap reference that can operate from supply voltages as low as 500 mV. This was achieved by using a switched capacitor charge pump, rather than resistors or current sources, to bias a pair of BJTs. The use of a charge pump also reduces the circuit’s minimum supply voltage. At an output voltage of 500 mV, it achieves a temperature coefficient of 45 ppm/^oC together with a PSRR that is well over 60 dB.

The potentials IoT embraces are not just enhancements over existing developments and commercial models; rather, they are transformational in total. The scope of this IoT economy will revolutionize the system industries' production and function. Additionally, the transformation is happening quicker than any previous industrial revolution. Simultaneously, IoT will present unique challenges across all multi-disciplinary sectors and for all industries.

As it resolves complications that have overwhelmed businesses for a significant amount of time, it will also produce entirely new problems, both procedural and ethical. Anxieties and concerns over confidentiality, cybersecurity, and privacy, as well as property and product liability, will quickly become just as robust as the opportunities IoT presents. While businesses must begin to implement IoT technology if they hope to survive over the long term, they also must implement strategies that account for the many risks associated with IoT.

Sources:

1. Van Helleputte, Nick, et al. "Advances in Biomedical Sensor Systems for Wearable Health." Hybrid ADCs, Smart Sensors for the IoT, and Sub-1V & Advanced Node Analog Circuit Design. Springer, Cham, 2018. 121-143.
2. Pamula, Venkata Rajesh, Chris Van Hoof, and Marian Verhelst. "An Ultra-low Power, Robust Photoplethysmographic Readout Exploiting Compressive Sampling, Artifact Reduction, and Sensor Fusion." Hybrid ADCs, Smart Sensors for the IoT, and Sub-1V & Advanced Node Analog Circuit Design. Springer, Cham, 2018. 145-163.
3. Ruffieux, David, et al. "A 32 kHz DTCXO RTC Module with an Overall Accuracy of±1 ppm and an All-Digital 0.1 ppm Compensation-Resolution Scheme." Hybrid ADCs, Smart Sensors for the IoT, and Sub-1V & Advanced Node Analog Circuit Design. Springer, Cham, 2018. 165-181.
4. Pan, Sining, and Kofi AA Makinwa. "Energy-Efficient High-Resolution Resistor-Based Temperature Sensors." Hybrid ADCs, Smart Sensors for the IoT, and Sub-1V & Advanced Node Analog Circuit Design. Springer, Cham, 2018. 183-200.
5. Sanjurjo, J. P., et al. "A High-Resolution Self-Oscillating Integrating Dual-Slope CDC for MEMS Sensors." Hybrid ADCs, Smart Sensors for the IoT, and Sub-1V & Advanced Node Analog Circuit Design. Springer, Cham, 2018. 201-218.
6. Tewari, Shikhar, and Aatmesh Shrivastava. "Ultra-low Power Charge-Pump-Based Bandgap References." Hybrid ADCs, Smart Sensors for the IoT, and Sub-1V & Advanced Node Analog Circuit Design. Springer, Cham, 2018. 219-236.

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