In the latest edition of TTP’s Inside:Technology journal, we reveal the secret ingredients that go into making our award-winning CO2 sensors! TTP – The Technology Partnership – comprises a team of scientists and engineers working together to invent, design and develop the next new big technology products and concepts.
Solid state CO2 detector
Gas Sensing Solutions Ltd (GSS) has launched a range of midinfrared light emitting diode (LED) and photodiode light source/detectors for measuring carbon dioxide emissions. What is different about the sensors is that they use solid-state light sources and detectors instead of incandescent light bulbs and pyro-electric detectors: this greatly reduces the amount of power and improves turn-on time from minutes to milliseconds.
The very fast stabilisation time means that where a measurement is only required every minute, the sensor is only powered up for 1/60 of the time (the time required to turn on the sensor from cold, stabilise, take and report a measurement, and power down again ˜1 second). By comparison, a ﬁlament bulb might take a minute to warm up, hence the solid state sensor has a radical energy advantage. A second beneﬁt is that the LEDs can be modulated rapidly, allowing high sampling rates of up to 100Hz – enabling new diagnostic applications in the medical and veterinary arena.
Novel optics design
A key aspect of GSS’s technology is the layout of the light wave guide. A long path through the gas being measured is essential for sensitive measurements, particularly at low concentrations; while shorter paths are required for very high concentrations of gas. GSS has developed wave guide designs which increase the optical path length making photo detection much more sensitive, while reducing the size. The patented optical structures enable high signal to noise ratios to be maintained at low LED power levels – further minimising the power consumption. Additionally, as the light source is a solid state component it is possible to miniaturise the PCB layout to the point where it is almost fully enclosed within the optical component’s footprint.
Advantages include the fact that when operating at 2Hz, the sensor consumes only 1.5mJ of energy per measurement, as compared with traditional sensors which typically require in excess of 100mJ per measurement. In addition, as a solid state device it has much longer life – as much as 25 years (compared with 5~15 for incandescent); this, combined with a small form factor, makes it very suitable for ‘ﬁt and forget’ applications. Thus while LED technology carries a small price premium over the incandescent lamps used in traditional sensors, total lifetime costs are improved due to the energy saving and much longer life.
Patents & IP
The company has ﬁled four worldwide patents which cover optical designs, pulse shaping and calibration techniques. There is considerable know how as well as IP in the different stages of the manufacturing process, starting with the front end epitaxy processing – where the recipe remains a closely-guarded secret. Since the company’s inception, in 2006, the efﬁcacy of the LED has been enhanced over 20 times, based on ongoing research into the III-V structures used. The calibration process is also complex, containing very signiﬁcant IP that turns a light source and detector into a highly accurate gas detector. As a result, the company’s IP position may open up interesting licensing models to pursue in the future.
The company was founded in 2006 by Alan Henderson, with initial funding provided by Tricap Investments and the Scottish Investment Bank – both of whom have continued to back the company since. Previous to the company’s formation Henderson had been working in defence offset programs with companies such as Pilkington. Soon after he formed GSS he was joined by the company’s CTO, Calum MacGregor.
The ﬁrst product – the C20 gas sensor – launched in 2007 – was able to demonstrate the low-power potential of LEDs in gas sensing. This attracted companies such as Schneider Electric to work with GSS and to focus on delivering low power sensors for wireless applications; subsequent products broadened the range, while the technology was recognised with multiple awards – including the Shell Springboard in 2012, followed by the prestigious Innovation Award from the Institute of Physics in 2014.
In 2016, the company recruited an outside CEO, Ralph Weir, in order to accelerate the company’s global expansion. Weir has a strong sales background, in addition to leadership experience. It makes his job easier he says that “the sensor’s performance knocks people off their feet”. He has to address the fact that “the business has great products which have been under-sold”. Accompanying an increased focus on selling, the company is about to expand production capacity in its Cumbernauld facility ﬁve-fold, on top of a doubling of capacity in the last six months of 2016.
Currently GSS grows the III-V epiwafers on its own MBE reactor, then despatches them to foundries which carry out further wafer processing, including metallisation & etching; other contractors then do the backend processing (dicing the wafers, and hybridisation) before shipping them to GSS for ﬁnal assembly. Other sensor components (electronics and optics) are similarly outsourced. The ﬁve-fold increase in production capacity requires doubling the production area and investment in increased automation.
CoZIR® Product Series:
The company launched its low power, CoZIR® product series in 2010.
CoZIR®: for applications such as heating, ventilation and air conditioning (HVAC), indoor air quality, and horticulture. It consumes 3.5mW in continuous operation, with two carbon dioxide measurements per second – prior to the launch of CoZIR®-LP, it was the world’s lowest power NDIR CO2 sensor; it is available with ranges of 0 to 2,000ppm, 0-5000ppm and 10,000ppm.
ExplorIR®: designed for harsh, demanding applications that require a super robust CO2 sensor. This includes process control, diving, industrial, safety and automotive applications. The robust ExplorIR® CO2 sensors are able to measure CO2 across the full range of gas concentration – from zero to 100% CO2.
SprintIR®: launched in 2015, is an ultra-high-speed CO2 sensor, which samples 20 measurements per second for applications requiring absolute real time CO2 response, such as temporal measurement of CO2 exhalation, in-ﬂow process control and analytical instrumentation.
The CoZIR®-LP was launched at the AHR EXPO in Las Vegas in January 2017. The upgraded version is intended for ambient air applications. It takes up only 15% of the physical volume of the earlier sensor and requires only 3mW of power with a peak pulse current of 33mA. It can address what GSS describe as the Achilles heel of CO2 sensors – life-time and replacement requirement; it also meets the trend for sensors to be self-powered, using power-scavenging technologies. Several customers are sampling the new sensor, including Sharp Electronics, who have demonstrated CO2 sensors running from photovoltaic cells for energy-harvesting HVAC controllers.
Air quality market
Currently the biggest market for GSS is Indoor Air Quality measurement and control, which is driven by existing and impending regulation to control and monitor CO2 emissions. CO2 gas is safe in low concentrations (typically <1,000 ppm), but prolonged exposure at moderate levels (>5,000 ppm) can lead to health related problems, such as sick building syndrome. Since products based on the GSS sensors can operate ‘autonomously’ – i.e. without hard wiring – they open up new opportunities, and in time may encourage the authorities to tighten indoor air quality legislation further. Examples of this include in the UK, BS6173 for the hotel industry, or California’s Title 24 regulations – which introduced an initial CO2 capability within Demand Controlled Ventilation (DCV) in 1996 – and have been continuously strengthened since.
Innovation in Respiratory Care
Although hundreds of millions of people globally suffer from chronic respiratory conditions, according to GSS there are currently no personal devices to help sufferers monitor their actual respiratory performance. What is happening during respiration is that the lungs inhale oxygen, the body converts it to carbon dioxide, and then the lungs exhale the carbon dioxide. Capnography, which is the measurement of carbon dioxide concentration during the respiratory cycle, is already an established technique used in critical care. To improve this GSS is working with a leading company in this ﬁeld, Cambridge Respiratory Innovations Ltd (CRiL) based on an advanced medical version of its fastest sensor.
CRiL’s respiratory sensor
CRiL’s N-Tidal personal respiratory monitor uses a bespoke GSS sensor, which due to its stability and accuracy, makes it possible to exploit an established but under-used biomarker for respiratory condition – tidal breathing CO2 waveform shape analysis. According to CRiL the ﬁrst clinical study in 2016 has delivered “hugely encouraging results, indicating that it can predict exacerbations in COPD by up to 48 hours”. GSS is continuing to support CRiL as it substantially expands its clinical research programme during 2017.
The GSS sensors offer great reliability in high-vibration environments because of their solid state components which make them largely immune to pressure variations, hence ideal for aircraft use. CO2 is used to control food ripening in transit or storage where end-user products range from packaging machines for bags of salad through to controlled-atmosphere shipping containers; in horticultural, CO2 can be used to help accelerate plant growth; it can also be used as pest control. In the diving industry, the “rebreather” is moving from professional-only use to the high-end leisure industry. “In reality, the applications are extremely diverse”, says Weir.
GSS is also considering the development of sensors for other gases, since its sensors can operate in the spectral range from 2.5 um to 6.0 um where many gases have absorption features. The range of future opportunities therefore continues to grow.
IoT Sensor Networks
GSS have been supplying CO2 sensors into wireless Building Management Systems for several years – mostly based on proprietary networks. Beyond this, IoT is opening up new thinking and new opportunities for deploying sensors cost effectively sometimes around buildings, but often around other locations. As a result demand for autonomous CO2 sensors which can work together in networks for real time, high-speed sensing and data acquisition – often integrating other sensors – is increasing. The low power of the GSS sensor is making them an early choice for IoT integrators. It therefore adds a further opportunity to expand sales signiﬁcantly over the coming years, and underlines the reason for the new CEO’s appointment.
Inside:Technology 2017: edition 1 www.ttp.com
Gas Sensing Solutions supplies the world’s fastest response and lowest power sensors for detecting CO2 gas.