5 research outputs found
A 0.18µm CMOS DDCCII for Portable LV-LP Filters
In this paper a current mode very low voltage (LV) (1V) and low power (LP) (21 µW) differential difference second generation current conveyor (CCII) is presented. The circuit is developed by applying the current sensing technique to a fully balanced version of a differential difference amplifier (DDA) so to design a suitable LV LP integrated version of the so-called differential difference CCII (DDCCII). Post-layout results, using a 0.18µm SMIC CMOS technology, have shown good general circuit performances making the proposed circuit suitable for fully integration in battery portable systems as, for examples, fully differential Sallen-Key bandpass filter
reliable and inexpensive solar irradiance measurement system design
Abstract In this work, we present an innovative low cost sensor and algorithm for the monitoring and measurement of solar irradiance. This parameter is usually estimated using pyranometers, often based on thermopile. They are quite expensive, also because need additional hardware for data acquisition and manipulation as well as non-negligible installation costs. The system architecture and novel algorithm here proposed employ small PhotoVoltaic (PV) cells and a digital sensor interface. Moreover, the logic section permits to tilt the sensor allowing to track the sun with improved accuracy
Dynamic Study of Flexible Sensors to Reduce Motion Artifacts
The field of wearable electronics is changing healthcare and increasing possibilities for human-machine interfaces. Soft electronics stretch with the skin to monitor long-term heart rate trends or direct the motion of smart prosthetics. The capabilities are only as good as the signal quality. A significant challenge for these devices is that by their very definition – wearable – these flexible sensors suffer from motion artifacts not previously found when measured in a stationary setting. This thesis investigates three significant sources of motion artifacts for flexible sensors: relative motion between sensor and signal source, the unique challenges of skin strain, and change in contact impedance. Relative motion is not a unique problem for wearable electronics. Still, human tissue's elastic nature means that most body-mounted sensors undergo more relative motion than on a comparable rigid machine. Device design and placement are analyzed to reduce the movement between the sensor and signal source. Dynamic effects of jogging are numerically simulated for a chest-mounted device showing a small form factor, and lightweight designs reduce device motion. Human skin is an unstable platform to mount devices. Skin strain causes device movement and changes the biopotential during measurement. Experimental examples show material and design solutions to increase adhesion, reduce strain within the device, and maintain breathability for long-term recordings. Flexible sensors measuring biopotential are susceptible to changes in contact impedance. Skin strain and vibrations create motion artifacts that can mimic or disrupt many biosignals, making them hard to filter out. A prototype device is presented that uses a strain isolating layer to reduce skin strain at the electrode, which stabilizes contact impedance and reduces motion artifacts. Experimental data from the device compensating for these three sources of motion artifacts is presented for quantitative comparison.M.S
A Photoplethysmography System Optimised for Pervasive Cardiac Monitoring
Photoplethysmography is a non-invasive sensing technique which infers instantaneous
cardiac function from an optical measurement of blood vessels. This
thesis presents a photoplethysmography based sensor system that has been developed
speci fically for the requirements of a pervasive healthcare monitoring
system. Continuous monitoring of patients requires both the size and power
consumption of the chosen sensor solution to be minimised to ensure the patients
will be willing to use the device. Pervasive sensing also requires that
the device be scalable for manufacturing in high volume at a build cost that
healthcare providers are willing to accept. System level choice of both electronic
circuits and signal processing techniques are based on their sensitivity to
cardiac biosignals, robustness against noise inducing artefacts and simplicity
of implementation. Numerical analysis is used to justify the implementation
of a technique in hardware. Circuit prototyping and experimental data collection
is used to validate a technique's application. The entire signal chain
operates in the discrete-time domain which allows all of the signal processing
to be implemented in firmware on an embedded processor which minimised the
number of discrete components while optimising the trade-off between power
and bandwidth in the analogue front-end. Synchronisation of the optical illumination
and detection modules enables high dynamic range rejection of both
AC and DC independent light sources without compromising the biosignal.
Signal delineation is used to reduce the required communication bandwidth as
it preserves both amplitude and temporal resolution of the non-stationary photoplethysmography
signals allowing more complicated analytical techniques to
be performed at the other end of communication channel. The complete sensing
system is implemented on a single PCB using only commercial-off -the-shelf
components and consumes less than 7.5mW of power. The sensor platform
is validated by the successful capture of physiological data in a harsh optical
sensing environment
A Photoplethysmography System Optimised for Pervasive Cardiac Monitoring
Photoplethysmography is a non-invasive sensing technique which infers instantaneous
cardiac function from an optical measurement of blood vessels. This
thesis presents a photoplethysmography based sensor system that has been developed
speci fically for the requirements of a pervasive healthcare monitoring
system. Continuous monitoring of patients requires both the size and power
consumption of the chosen sensor solution to be minimised to ensure the patients
will be willing to use the device. Pervasive sensing also requires that
the device be scalable for manufacturing in high volume at a build cost that
healthcare providers are willing to accept. System level choice of both electronic
circuits and signal processing techniques are based on their sensitivity to
cardiac biosignals, robustness against noise inducing artefacts and simplicity
of implementation. Numerical analysis is used to justify the implementation
of a technique in hardware. Circuit prototyping and experimental data collection
is used to validate a technique's application. The entire signal chain
operates in the discrete-time domain which allows all of the signal processing
to be implemented in firmware on an embedded processor which minimised the
number of discrete components while optimising the trade-off between power
and bandwidth in the analogue front-end. Synchronisation of the optical illumination
and detection modules enables high dynamic range rejection of both
AC and DC independent light sources without compromising the biosignal.
Signal delineation is used to reduce the required communication bandwidth as
it preserves both amplitude and temporal resolution of the non-stationary photoplethysmography
signals allowing more complicated analytical techniques to
be performed at the other end of communication channel. The complete sensing
system is implemented on a single PCB using only commercial-off -the-shelf
components and consumes less than 7.5mW of power. The sensor platform
is validated by the successful capture of physiological data in a harsh optical
sensing environment