Talks

Hayden Callow

KONGSBERG MARITIME

Seabed mapping with HISAS –
a synthetic aperture sonar

A brief history of synthetic aperture sonar at KM will be presented with real world data.  
We will describe the challenges of making highly sensitive sensor systems that operate robustly under all conditions.  
HISAS combines sensor data from vertically stacked arrays to create precise bathymetric measurements needed for accurate imagery.  
High-resolution acoustic imagery of shipwrecks may be difficult to interpret and challenge fundamental assumptions of side-looking sonars.  
We explore ways of computing and visually presenting the full picture of the seabed.

Ola Nilsen

UNIVERSITY OF OSLO

ALD as a key enabler of novel materials in MEMS-sensor application

The talk will describe how one of the world's smallest pressure sensors is now being brought from R&D to a commercial product that will improve diagnostics for millions of people around the world who struggle with bladder problems. Being able to monitor bladder pressure over time based on natural filling cycles is expected to be a gamechanger in the field of urology.

Henrik Jacobsen

USN

History and Perspectives for high performance Piezoresistive Silicon Pressure Sensor Technology for World Niche Markets

The discovery of piezoresistive effect in 1954 paved the way for production of silicon-based sensors. In Norway we started research on the piezoresistive effect in silicon around 1960 and the first industry products was developed and set into small scale production by Advanced Micro-Electronics (AME) less than 10 years later. There has been a continuous development of silicon sensors in Norway since then, and a variety of successful products have been developed. This presentation will give an historic overview of early work on silicon sensors in Norway and on the sensor technology that has been developed by Sensonor AS from 1985 and optimized and refined for a variety of demanding niche applications. Today this technology is used in a variety of high-performance applications worldwide. More than 1 bill. tire pressure sensors have been delivered and used in passenger cars all over the world during the last 20 years. New and more optimized versions of this technology is now under development and industrialization by MEMSCAP AS and Sensonor for manufacturing of ultra-high accuracy sensors and transducers for new profitable niche aerospace, industrial and medical applications.

Matthieu Lacolle

SENSIBEL

Applications of high-SNR optical MEMS microphones

sensiBel is a scale-up company commercializing an optical MEMS technology that originated from SINTEF and was developed further at sensiBel during the last five years. The company’s first product is a MEMS microphone offering true studio-qualityaudio in a small-size MEMS package, basically matching the performance of a high-end professional microphone, a combination that is enabled by the interferometric optical readout that is at the core of sensiBel’s technology. In this presentation, we will describe the key performance parameters of the SBM100 series of optical MEMS microphones, as well as how these can benefit a variety of audio applications.

Christopher Dirdal

SINTEF

Reconfigurable metasurfaces for next generation integrated photonic devices

What if we could make optics in the same way that we make electronics? The development of Silicon technology for batch processing of electronic circuitry has since the 1960s allowed for exponential growth in computation power while simultaneously causing prices to drop like a stone. Few back then would have imagined the computational power currently carried around on our wrists in the form of smart watches at price points relevant for the annual Christmas or birthday gift. A similar revolution is currently happening today with the emergence of metasurfaces, a recent development within nanophotonics which is transforming both the capabilities of miniature optical sensor and imaging systems and how they are fabricated.  They consist of resonant plasmonic or dielectric nanostructures which are tailored to give unprecedented control of reflected and transmitted light. Among almost ten thousand publications[1] on the topic of metasurfaces since 2010 a myriad of optical functions has already been demonstrated, including gratings, lenses, mirrors, holograms, waveplates, polarizers, and spectral filters[2]. A significant advantage of metasurfaces is that they can be multifunctional[3]: integrating several functionalities into a single surface where conventional optical systems require several. Furthermore, metasurfaces can be subwavelength thin and can be batch processed using standard micro- and nanofabrication techniques at potentially low-cost. These properties combined make metasurfaces suited for ultracompact optical devices, e.g. through integration into the production lines of e.g. image detectors and light sources such as LEDs and VCSELs. For this reason, miniature metasurface lenses were recognized as one of top ten emerging technologies by World Economics Forum[4] in 2019.
So far, the vast majority of publications on metamaterials consider systems that are static – i.e. the optical functionality is locked after fabrication. A form of tunability which can be integrated into silicon processing technology is offered by Micro-Electro-Mechanical-Systems (MEMS). These allow for electrically controlled mechanically moveable parts in a chip-based sensor or imaging device.  With integration into silicon technology, MEMS are compatible with the high-volume batch processing needed for reducing size, cost and weight of the optical systems. Recently MEMS actuation have been added to metasurfaces enabling for instance tunable lenses[5],[6], as also we have done in our current article. Our contribution in this respect is to introduce a new form of MEMS actuation to metasurfaces: Thin-film piezoelectric film actuation with lead zirconate titanate (PZT). This allows for twice the displacement at a quarter of the voltage, compared to state-of-the-art5: 7.2µm displacement at a voltage application of 23V. Furthermore, thin-film piezo-MEMS actuation is fast (>kHz) and low power, thereby relevant for a wide range of mobile applications. 

Karl Henrik Haugholt

SINTEF

Custom-designed Flash LIDAR for 3D measurements underwater and in Space

The background and history of flash lidar activities at Sintef will be presented. A flash lidar is a 3D camera using a short or modulated laser pulse to do time of flight measurements. 

The uniqueness of our system is that the sensor can be made with standard CMOS processes and it has megapixel resolution. The range can be in the range of metres to kilometres, with resolution in the cm range. The high computational power available today allows advanced algorithms to be implemented.   

  

Our first flash lidar for under water applications was realised in the EU project UTOFIA (www.utofia.eu[eur03.safelinks.protection.outlook.com]) together with several international partners. The UTOFIA unit is 7 litres and 9 kg. It typically has a range of 10 meters, and gives 3D images at 10 Hz. UTOFIA was designed as an underwater camera for 3D imaging of aquaculture or seabed subjects at close range. For this application, sub-centimetre resolution was obtained, corresponding to <100ps resolution of pulse arrival time. Considerable effort went into developing hardware and algorithms that could deliver such accuracy. Some performance examples will be shown.

 

The success of UTOFIA led to a project for ESA to adapt the system to space applications. Current space applications require much longer distances. To address this, we apply our experience in handling in low SNR conditions in underwater applications. The main challenge is to deliver sufficient precision in position and velocity at > 1 km range. The UTOFIA system was selected by ESA as a potential candidate to meet performance requirements for future exploration missions.

Balpreet Singh Ahluwalia

UiT

On-chip super-resolution optical microscopy: The Big Picture

Seeing is believing, since its discovery optical microscopes have been the backbone of life sciences and medical biology. Recent advances has allowed researchers to acquire super-resolution images of nanoscale biological phenomena, using an optical microscope, albeit at a high-cost and with a low-throughput.  Here, we present activities from our group where we harness photonic integrated circuits to deliver on-chip super-resolution optical microscopy with 100X large throughput enabling researcher to draw statistically relevant biological conclusion to have the big picture! 

Peter James Thomas

NORCE

Distributed fibreoptic sensors and their applications

Distributed fibre optic sensors possess a unique set of characteristics, making them particularly suited for harsh environments and applications where providing power and communication for large numbers of individual sensors presents a challenge. This talk presents some of NORCE's activities in technology development and applied research towards distributed fibre sensors, covering applications including renewable energy, environmental monitoring, transport, and oil & gas. 

Angela Kok

SINTEF

Silicon microdosimetry for radiation therapy and radiation protection

New cancer treatment like proton and heavy ion therapy are highly localised and is essential to combat the continued increase of cancer cases worldwide. The localisation significantly reduces the received dose in healthy tissues surrounding a cancerous tumour, thus providing improved prognosis for cancer patients.  The use of this type of advanced therapy, however, comes with new challenges in treatment planning and QA.  Using a combination of modern micromachining techniques and radiation sensor technology, sensitive volumes that mimic biological cells have been designed, prototyped, and demonstrated to be an attractive candidate for providing improved dosimetry in particle therapy.  The technology has also raised high interests for radiation protection in harsh environment such as lunar exploration.  This talk will discuss the core of this unique sensor technology and their potential applications in radiation therapy and radiation protection.

Trond Løke

NEO

Quality leading hyperspectral systems from Norway

For the last 20 years, NEO has been leading in designing and developing hyperspectral imaging systems through their brand HySpex. Spectral fidelity per pixel is imperative when designing trustworthy and reliable systems for the remote sensing industry (field, UAV and airborne), laboratory use and industrial application. The requirement for quality to solve real-world applications is demanding and requires the supplier to take a high degree of care from the design process through production. This presentation will focus on key aspects of hyperspectral imaging technology as well as NEO and HySpex’ journey in this marketplace, how we have positioned ourselves in the market space and what we have done to get where we are today.

Benoît Piro

UNIVERSITÈ DE PARIS CITÈ

Electrochemical sensors

Among many different kinds of electronic transducers for bioprobe-biotarget interactions, field-effect transistors (FETs) are among the most promising candidates. ISFETs were largely applied for monitoring biological events, e.g. pH changes produced by the activity of an enzyme. However, organic electrochemical transistors (OECTs) and electrolyte-gated organic field effect transistors (EGOFETs), transistors where the dielectric material is replaced by an aqueous solution and operating voltages of a few hundreds of mV, opened the way for applications in water or even in or on living organisms. Just as examples, such transistors are able to transduce capacitive events occurring whether at the electrolyte/semiconductor interface or at the gate/electrolyte interface, such as antibody/antigen interactions or DNA aptamers/small organic molecules or proteins. We also demonstrated that a water-gated OFET is able to amplify the current coming from a microalgae’s photosynthetic activity placed on the gate electrode; a property that can be applied for monitoring the action of pesticides on living organisms. In the meantime, driven by the development of new functional inks, inkjet-printed electronics has reached several milestones, so that it is now possible to fabricate these transistors by mean of printing.

Svein-Erik Hamran

UNIVERSITY OF OSLO

The RIMFAX radar on board the NASA Perseverance Mars rover

The NASA rover Perseverance landed in Jezero Crater on Mars February 18, 2021. The main objective for the rover mission is to search for possible ancient life on Mars and to collect rock samples for return to Earth. The University of Oslo operates the RIMFAX ground penetrating radar onboard the Perseverance and is using it to study the Martian subsurface.

Svein-Erik Hamran is Professor at the Department of Technology Systems and Director of the Center for Sensors and Systems – CENSSS at the University of Oslo. He is the Principal Investigator of the RIMFAX Ground Penetrating Radar on the NASA Mars 2020 Perseverance Rover Mission.

Lasse Vines

UNIVERSITY OF OSLO

Quantum sensing using defects

Using quantum phenomena to measure a physical quantity may enhance both sensitivity and precision. Such quantum sensing (QS) has become a distinct and rapidly growing branch of research within the area of quantum technology, promising applications including magnetometry, electrometry, thermometry, and chemical sensing. Prominent platforms for QS are superconducting junctions, trapped ions, and semiconductors hosting quantum dots or point defects, where the latter offer a wafer platform suitable for scaling, miniaturization, and room temperature operation, and is therefore of particular interest. The most developed point defect candidate for QS applications, and QT in general, is the nitrogen-vacancy (NV) color center in diamond, but quantum defects in industrially friendly materials like silicon and silicon carbide are rapidly gaining ground. In this presentation, the use of point defects in semiconductors for sensing application will be discussed.

Ivar Kristian Waarum

NGI

Smart AUVs for efficient marine environmental monitoring

Autonomous Underwater Vehicles (AUVs) may seem like the silver bullet that allows to increase the scope and ambitions for implementation of offshore environmental monitoring – they can cover large volumes of water, do surveys that last for days, weeks and months and carry a steadily growing number of different sensor technologies. However, a key to successful implementation of an environmental monitoring system, is to understand which parameters are important to monitor, their short- and long-term natural variability, and not least how the sensing technology works and is affected by the environment and method of deployment. Through the last decades, NGI has led or been involved in several marine environmental monitoring projects where chemical, acoustic and oceanographic sensors have been deployed offshore and nearshore. Based on experiences from these projects, we point to challenges that has to be overcome and benefits that can be reaped with the realisation of truly autonomous – or smart – AUVs as a sensor platform. The presentation highlights some aspects of deployment and operation of selected sensor technologies on stationary and mobile sensor platforms, and how the type of sensor platform affects sensor performance. We identify some features of AUVs that are steps towards smart AUVs and a sketch of how these features will be realised in an upcoming project to be particularly useful for environmental monitoring of offshore CO2 storage and leakage detection from legacy wells.

Torstein Dalen-Lorentsen

SINTEF

Use of sensors to monitor load and enhance performance in elite sports

The use of sensors to monitor activity and recovery has become an integral part of everyday life in elite sports. Data from sensors is used to support decision making to increase performance and prevent health problems. This talk will discuss the current use and the future potential of sensors to influence performance and prevention, as well as the transferability to other research and business areas.

Espen Eek

NGI

Why in situ sensing of trace chemicals in natural media is so hard: Examples of progress using a novel sensor system and the combination of existing sensors

Real-time sensors have become more and more important in our everyday life as sensors to record many physical parameters have become increasingly matured technology. Such sensors are therefore integrated in everyday products as well as in many industrial processes. Real-time sensors for measurements of chemical parameters have also existed for decades. However, while methods for laboratory analysis have been developed for determination of numerous micro-pollutants in environmental media such as air, water and soil, very few real-time alternatives exists for these parameters. 
This presentation will discuss the challenges of real-time sensing of chemical micro-contaminants in the environment as well as potential solutions by miniaturization of selected separation and concentration processes used in laboratory methods as well as the gains of using different sensors in combination. Results from real-time in situ measurement of ng/L PAHs in the sea outside a produced water discharge in the North Sea will and improved leakage detection using be presented.  

Ørjan Grøttem Martinsen

UNIVERSITY OF OSLO

Impedance based sensors for biomedical applications – from mHz to GHz

The passive, electrical properties of biological materials are highly influenced by the anatomy and physiology of the tissue and bioimpedance measurements can hence be used for characterization or diagnostication. This lecture will give a brief introduction to electrical bioimpedance and then give examples from different biomedical applications. A particular focus will be put on recent developments in microwave relaxation spectroscopy for label free detection of polar, non-electroactive molecules.  

Guido Sordo

SINTEF

High performance MEMS strain gauge sensor for structural monitoring

The presentation will focus on ongoing research activity carried out at SINTEF Digital on MEMS strain gauges. Extending the lifecycle of an asset, and also ensuring that the asset functions efficiently and without failure for most, if not all, of this lifecycle, is a key concern for many businesses. This is now turning into an expanding market for condition monitoring sensors. Among the various parameters that could be monitored, strain is one of the most interesting since it is strongly connected to most failures affecting the reliability of infrastructures. However, such mechanical measurement is extremely challenging since the sensor needs to be in close contact with the element to be monitored, which imposes constraints in terms of packaging and materials. The strain measurement from a single position is valuable, but monitoring the distribution of strain over the structure would increase this value many times over. This can be accomplished by using a distributed sensor network which would enable more advanced and effective analysis of the mechanical element. However, a network of nodes introduces challenges in terms of data collection and synchronization among nodes. In specific applications of interest, e.g. offshore infrastructures, the energy usage within the network also needs to be addressed at all levels.

Erik Johannessen

USN

Current trends in BioMEMS

This talk will offer a perspective on BioMEMS ranging from early work on protein based devices such as enzyme sensors and associative volumetric memories to more recent lab-on-a-chip and microfluidic systems governing the behaviour of protozoans. Examples of the use of microsystems designed for a generic high-density primary screen assay of bioactive compounds using mammalian cells will be explored. Autonomous systems based on radiotelemetry devices (electronic pills), and point of care devices designed to perform real time measurements in the human body will also be presented. Concluding remarks will offer a perspective on future and emerging trends to come.

Chi Kwong Tang

TOMRA

From LED to reverse vending machine; Optical systems, component scarcity, tuneable LED and production

TOMRA Collection design and builds reverse vending machines that facilitate the collection of used beverage containers. The focus on competence in research and development ensures rapid adaptation of new systems, using mainly basic components. Even in a time of component scarcity, a new method for tuneable LED is developed and successfully launched. The stories from design to test and production of different optical systems are reviewed in the light of an unusual year

Jenny Picalausa

SONY

CMOS image sensors designed for Automotive Cameras

Automotive cameras capture high quality video to extend visibility and enhance the safety of the driver. These cameras are used to assist the driver for parking, for accident avoidance, for night vision, and to gather critical evidence. This presentation will focus on the image sensor technologies and design techniques used to meet thechallenging requirements of the automotive industry, for instance the need for extremely high dynamic range (120-140dB) compared to regular cameras.

Martin Ingvaldsen

ZIVID

High performance 3D imaging for automation and inspection

We provide an overview of 3D measurement technologies and their applications within automation, and presents the rationale of Zivid choosing structured light as their core technology for factory automation. We present some of the core challenges that must be managed in order to create a high-precision, reasonably priced 3D camera for the automation industry. We also outline how 3D cameras fit into the overall value chain of automation.

Thor Bakke

TUNABLE

Tunable MEMS filters and their applications in infrared spectroscopy

Microchips that provide wavelength tuning of infrared light will be presented. Key qualities of these MEMS filters include tuning range, precision, and robustness, making them ideally suited for various applications in infrared spectroscopy, such as miniaturized multi-gas analyzers. 

Jens Petter Wold

NOFIMA

Design of spectroscopic smart sensors for quality assessment of heterogeneous foods.

Representative sampling is often a limitation with spectroscopic methods regarding heterogeneous foods. Surface measurements work well on continuous streams, but when single products need to be characterized, such as chicken fillets, fish fillets or crabs, we meet challenges due to heterogeneity of the products. The surface is usually not representative for the interior of the sample. In this talk I will present and discuss the challenges of heterogeneity and how they can be solved by novel and tailor-made instrumentation. Some of the presented examples are now well working smart sensors in the food industry.

Anders Hansen

SINTEF

Novel Sensors for Quality Classification of Strawberries in the Field

Strawberry horticulture is rapidly becoming a worldwide industry, but short maturation windows, limited shelf life, and vulnerability to pests are major challenges to yield and profitability. In the NRC-funded project MålBær, Saga Robotics in collaboration with SINTEF, Nofima and NMBU is developing sensor solutions that will monitor the quality of strawberry plants during growth and harvest. The goal is to quickly detect and remove diseased berries, and to ensure that healthy berries are harvested at optimal ripeness. In this talk, we will present the enabling sensor technologies for achieving this.

Dirk Meier

IDEAS

Multi-spectral Microbolometers

Integrated Detector Electronics AS, IDEAS, develops in collaboration with partners a multi spectral room temperature thermal infrared image sensor. 
As part of this collaboration IDEAS develops the SPEKTIR A2V12 (IDE5201), a carrier ASIC for a 640x480 microbolometer array (MBA). 
The 12 um pixel sensors are based on MEMS microbolometer technology developed by our partner which allows tuning the response to specific parts of the spectrum. 
The MBA carrier is developed in 180nm CMOS technology with a passivation module specialized to support MEMS manufacturing.
Wafer shot-maps and die layout can accommodate both wafer scale and chip scale vacuum packaging.
 
The carrier ASIC hosts a digital sequencer, and analog circuits (bias, references, column integrators, column CDS and multiplexing). The chip has 2 analog outputs providing pixel data at 10 Msps, supporting full-frame rates up to 60 fps. The target power consumption of the in-development ASIC is approximately 35 mW. 
 
A major challenge for thermal image sensors is to achieve the required figure of merit, that is the Noise Equivalent Temperature times the readout speed.  A design goal for this ASIC is to minimize power consumption but keep it as stable as possible to avoid temporal thermal fluctuations. The core array has several peripheral pixel rings to support removal of background signals, this includes blind pixels and skimming pixels to assist in removal pixel self-heating effects.

Patrik Johansson

CHALMERS

Nano-Plasmonic Battery Sensing and Monitoring

To enable more efficient usage of batteries, proper assessment of e.g. state of charge and state of health are crucial. Today the battery management system uses estimates based on external temperature, voltage and current. Sensors based on nano-plasmonics do open the path towards internal cell measurements. At the proof-of-concept level I will here show both how we can assess different electrolytes ex situ, how the sensor can be included in a coin-cell, and finally operando correlation between optical and electrochemical signals, monitored simultaneously in real time.

Magnus Wines

NOVELDA AS

Human presence detection using UWB sensing technology

Human Presence Detection (HPD) is an important feature of smart environments and user interfaces. The ability to seamlessly interact with smart infrastructure and devices using minimal effort is highly desirable in this context. Ultra-wideband (UWB) sensing technology offers unique features enabling non-contact and robust detection of human presence through measuring very small movements combined with accurate ranging. This presentation will give an introdution to UWB technology as an electromagnetic sensor including its fundamentals properties and how the wide bandwidth of the transmitted radio pulse converts into accurate range and velocity. A highly miniaturized and low-cost UWB HPD sensor for mass-market applications will be introduced along with selected use-cases examples. Future direction and new emerging applications will also be covered. 

Martin Peacock & Even Zimmer

ZIMMER & PEACOCK

Electrochemical Biosensors, the technology between biology and digitization

Electrochemical biosensors are the purest technology bridge between the real world in which we live in and the digital and information world in which we work and make decisions. An electrochemical biosensor can be fabricated to be sensitive and selective to the biology of interest, whilst the direct output of an electrochemical biosensor is an electrical signal be it a potential (voltage), current, or impedance (resistance. The flow of signal to information in electrochemical biosensing follows the same path irrespective of the actual electrochemical modality, where the generic path is: raw electrical signal, analogue measurement, conversion to digital data, transmission of digital data to the Cloud, conversion of the data to information in the Cloud, contextualisation of information with other data streams, transmission of contextualized  information to smart system or end-users via application programme interface (API). ZP will be presenting modern electrochemical biosensing from MedTech to AgTech.

Ann Elisabeth Albright Blomberg

NGI

Vibration monitoring in Narvik- using multi-sensor data in real time to optimize industrial operations (VIBMON)

LKAB is an international mining group committed to providing carbon-neutral steel production by 2025. While most of the mining takes place in Kiruna, steel pellets are transferred by train to the small town of Narvik and temporarily stored in silos extending 40-60 meters vertically into bedrock. The process of pellets being released from the freight train into the silos below, and further from the silo onto a transportation system directly below the silo, causes vibrations that reach and sometimes disturb the local community. There is a great interest in understanding the cause and nature of these vibrations so that they can be avoided or reduced to acceptable levels. An advanced vibration monitoring system (VIBMON) has been designed by the Norwegian Geotechnical Institute (NGI) in close collaboration with LKAB and is currently being installed in Narvik. The VIBMON system consists of 25 tri-axial accelerometers installed in 55 m deep boreholes, in tunnels below and beside one of the silos, and in nearby housing areas. Data is acquired continuously at a sample rate of 1 kHz from all 75 channels, and embedded processing ensures that key parameters are computed allowing operators to interpret the data in real-time. Trigger functionality ensures that undesired vibrations are identified, and high-resolution data stored for subsequent analysis. The system is designed for a lifetime of at least 20 years. In this talk we present the VIBMON system and discuss some of the significant challenges encountered when installing a monitoring system of this scale in a harsh environment. 

Knut Aasmundtveit

USN

Infrared cameras: SLID Intermetallic bonding for wafer-level vacuum sealing of MEMS bolometers 

MEMS bolometers for infrared cameras require vacuum sealing for accurate operation. Cu-Sn Solid-Liquid Interdiffusion (SLID) bonding is well suited, as the bondline consists of thin, well-defined layers of Cu and intermetallics, surviving the high post-processing temperatures typically used for getter activation. SLID bonding is compatible with wafer-level processing, allowing efficient manufacturing. The talk will show USN’s contributions to the EU project “APPLAUSE”, as well as an overview of SLID material systems, properties and applications. 

Ingelin Clausen

INVIVO BIONICS

MEMS pressure sensor revolutionizing insight into bladder function for millions of people

InVivo Bionics has a patented solution for continuous long-term bladder pressure monitoring. The technology is based on more than 10 years of R&D at SINTEF. 

Roy Grelland

MEMSCAP

Ultra high stability pressure sensors for the aerospace market

Based on the early development of piezoresistive sensors in the late 1060s, Memscap has been on a constant journey to optimize and develop products for the highly competitive aerospace market. Reilability and ultra high stability are the key requirements, and combined with an industry that is very conservative when it comes to changes and new technology, this talk will describe Memscap’s path through the development stages leading up to todays status where Memscap is in the forefront when it comes to offering ultra high stability solutions for this demanding market.

Geir Bjørnsen

USN

Manufacturing of Piezoresistive Pressure Sensors

Piezoresistive Pressure sensors have been developed and produced in Norway for more than 30 years. Such sensors consist of a thin silicon membrane with implanted resistors and conductors. They can be absolute or relative, depending on the sensor design and the integration method. This talk will give a brief description of different manufacturing processes of such sensors and some examples of packaging to have a stable sensing system.