22-05-2014, 02:45 PM
SMART SENSORS
[attachment=63535]
Abstract
This report discusses general architecture of smart sensor and the usefulness of silicon technology in smart
sensor. This report also pays attention to the importance and adoption of smart sensors. In addition to this
an effort is made to present the design consideration of smart sensor as per the functions performed. The
discussion will conclude with some examples of smart sensor.
Introduction
The advent of integrated circuits, which became possible because of the tremendous progress in
semiconductor technology, resulted in the low cost microprocessor. Thus if it is possible to design a low
cost sensor which is silicon based then the overall cost of the control system can be reduced .We can have
integrated sensors which has electronics and the transduction element together on one silicon chip. This
complete system can be called as system-on-chip .The main aim of integrating the electronics and the
sensor is to make an intelligent sensor, which can be called as smart sensor. Smart sensors then have the
ability to make some decision. Physically a smart sensor consists of transduction element, signal
conditioning electronic and controller/processor that support some intelligence in a single package [1]. In
this report the usefulness of silicon technology as a smart sensor, physical phenomena of conversion to
electrical output using silicon sensors, characteristics of smart sensors. A general architecture of smart
sensor is presented.
Usefulness of Silicon Technology in Smart Sensor
There are very convincing advantages of using silicon technology in the construction of smart sensor. All
integrated circuits employ silicon technology. A smart sensor is made with the same technology as
integrated circuits. A smart sensor utilizes the transduction properties of one class of materials and
electronic properties of silicon (GaAs). A transduction element either includes thin metal films, zinc oxide
and polymeric films. Integrating electronics circuits on the sensor chip makes it possible to have single chip
solution. Integrated sensors provide significant advantages in terms of overall size and the ability to use
small signals from the transduction element [1]. The IC industry will get involved in smart sensor if a very
large market can be captured and the production of smart sensor does not require non-standard processing
steps.
Signal conversion effects
We know that silicon shows a suitable physical signal conversion effect. Many of the physical effects of
silicon can be used in making sensors. Based on these effects, different types of sensors can be constructed
which can be used for measuring different physical and chemical measurand.
Table1 below shows how different non electrical signal in which we can classify different measurand and
Table 2 shows the physical effects for sensors in silicon [2].
Description of Smart Sensor Architecture
Architecture of smart sensor is shown. In the architecture shown A1, A2...An and S/H1, S/H2...S/Hn are
the amplifiers and sample and hold circuit corresponding to different sensing element respectively. So as to
get a digital form of an analog signal the analog signal is periodically sampled (its instantaneous value is
acquired by circuit), and that constant value is held and is converted into a digital words. Any type of ADC
must contain or proceeded by, a circuit that holds the voltage at the input to the ADC converter constant
during the entire conversion time. Conversion times vary widely, from nanoseconds (for flash ADCs) to
microseconds (successive approximation ADC) to hundreds of microseconds (for dual slope integrator
ADCs). ADC starts conversion when it receives start of conversion signal (SOC) from the processor and
after conversion is over it gives end of conversion signal to the processor. Outputs of all the sample and
hold circuits are multiplexed together so that we can use a single ADC, which will reduce the cost of the
chip. Offset compensation and correction comprises of an ADC for measuring a reference voltage and other
for the zero. Dedicating two channels of the multiplexer and using only one ADC for whole system can
avoid the addition of ADC for this. This is helpful in offset correction and zero compensation of gain due to
temperature drifts of acquisition chain. In addition to this smart sensor also include internal memory so that
we can store the data and program required.
Conclusions
In conclusion, silicon is very suitable material for fabrication of smart sensors. But still a lot of research is
required to get benefits of the smart sensor, but from the experience of already existing devices, we can
expect that in the coming decade a large number of successful smart sensors will emerge.
[attachment=63535]
Abstract
This report discusses general architecture of smart sensor and the usefulness of silicon technology in smart
sensor. This report also pays attention to the importance and adoption of smart sensors. In addition to this
an effort is made to present the design consideration of smart sensor as per the functions performed. The
discussion will conclude with some examples of smart sensor.
Introduction
The advent of integrated circuits, which became possible because of the tremendous progress in
semiconductor technology, resulted in the low cost microprocessor. Thus if it is possible to design a low
cost sensor which is silicon based then the overall cost of the control system can be reduced .We can have
integrated sensors which has electronics and the transduction element together on one silicon chip. This
complete system can be called as system-on-chip .The main aim of integrating the electronics and the
sensor is to make an intelligent sensor, which can be called as smart sensor. Smart sensors then have the
ability to make some decision. Physically a smart sensor consists of transduction element, signal
conditioning electronic and controller/processor that support some intelligence in a single package [1]. In
this report the usefulness of silicon technology as a smart sensor, physical phenomena of conversion to
electrical output using silicon sensors, characteristics of smart sensors. A general architecture of smart
sensor is presented.
Usefulness of Silicon Technology in Smart Sensor
There are very convincing advantages of using silicon technology in the construction of smart sensor. All
integrated circuits employ silicon technology. A smart sensor is made with the same technology as
integrated circuits. A smart sensor utilizes the transduction properties of one class of materials and
electronic properties of silicon (GaAs). A transduction element either includes thin metal films, zinc oxide
and polymeric films. Integrating electronics circuits on the sensor chip makes it possible to have single chip
solution. Integrated sensors provide significant advantages in terms of overall size and the ability to use
small signals from the transduction element [1]. The IC industry will get involved in smart sensor if a very
large market can be captured and the production of smart sensor does not require non-standard processing
steps.
Signal conversion effects
We know that silicon shows a suitable physical signal conversion effect. Many of the physical effects of
silicon can be used in making sensors. Based on these effects, different types of sensors can be constructed
which can be used for measuring different physical and chemical measurand.
Table1 below shows how different non electrical signal in which we can classify different measurand and
Table 2 shows the physical effects for sensors in silicon [2].
Description of Smart Sensor Architecture
Architecture of smart sensor is shown. In the architecture shown A1, A2...An and S/H1, S/H2...S/Hn are
the amplifiers and sample and hold circuit corresponding to different sensing element respectively. So as to
get a digital form of an analog signal the analog signal is periodically sampled (its instantaneous value is
acquired by circuit), and that constant value is held and is converted into a digital words. Any type of ADC
must contain or proceeded by, a circuit that holds the voltage at the input to the ADC converter constant
during the entire conversion time. Conversion times vary widely, from nanoseconds (for flash ADCs) to
microseconds (successive approximation ADC) to hundreds of microseconds (for dual slope integrator
ADCs). ADC starts conversion when it receives start of conversion signal (SOC) from the processor and
after conversion is over it gives end of conversion signal to the processor. Outputs of all the sample and
hold circuits are multiplexed together so that we can use a single ADC, which will reduce the cost of the
chip. Offset compensation and correction comprises of an ADC for measuring a reference voltage and other
for the zero. Dedicating two channels of the multiplexer and using only one ADC for whole system can
avoid the addition of ADC for this. This is helpful in offset correction and zero compensation of gain due to
temperature drifts of acquisition chain. In addition to this smart sensor also include internal memory so that
we can store the data and program required.
Conclusions
In conclusion, silicon is very suitable material for fabrication of smart sensors. But still a lot of research is
required to get benefits of the smart sensor, but from the experience of already existing devices, we can
expect that in the coming decade a large number of successful smart sensors will emerge.