The SENSORS which we dealt with till now, are capable of manipulation and computation of sensor derived data. They read the parameter for which they have been made , measure and present it in analog or digital format using an ADC converter. Depending on the need , the data may be fed to a microcontroller or any other device for performing specific tasks or calculations.
However , a SMART SENSOR can be seen as a level upgradation to the functionalities of SENSOR.
Simply , SENSOR + INTERFACING CIRCUIT = SMART SENSOR ;
A smart sensor is an analog or digital transducer combined with sensing and computing abilities. It consists of a transduction component, signal conditioning electronics, and a processor that supports some intelligence in a single package. This integrated device sensor, which has electronics and the transduction element jointly on one Si wafer, is known as system-on-chip.
Some of the enahanced capabilities of a smart sensor compared to a normal sensor is as follows :
MULTISENSING : A single smart sensor can be engineered to measure presseure, temperature, humidity , gas flow etc.,.
COMPUTATION : One can obtain average , variance , standard deviation for given set of sensor data.
SELF-CALIBRATION : Adjust deviation of output of sensor from desired value .
COST-EFFECTIVE : Possess less hardware with advanced functional capabilities making a smart sensor cost effective ..
Now comes the main part. Let us get to know the technologies involved in making the sensor ‘smart’ and ‘intelligent ‘ ..
WORKING OF A SMART SENSOR :
The most significant and essential component of a smart sensor system is its microprocessor. They carry out a large multitude of functions such as ADC conversion of sensor data , its processing , runs algorithms , modifies / delete any part of the data at periodic intervals to minimize power consumption and for long-term storage.
There are many other technologies that are incorporated and function along smart-sensor system that is responsible for providing the smart sensor its upgraded functionalities and miniaturisation. However, the key technologies responsible are :
MEMS – MICRO ELECTRO MECHANICAL SYSTEM :
It is the system of miniaturised mechanical and electro-mechanical elements that are made using techniques of microfabrication. The whole smart sensor is miniaturized using mems which also at the same time senses, processes and stores large amount of data. The major advantages of MEMS technology include minimizing energy and materials, enhanced reproducibility, improved accuracy as well as increased sensitivity and selectivity.
VLSI – VERY LARGE SCALE INTEGRATION TECHNOLOGY :
VLSI is the process of miniaturization of computer chips and engineering large number of transistors gates on a single silicon semiconductor wafer. VLSI has many advantages such as reducing the size of circuits and the cost of the devices, increasing the operation speed of the circuit and handling complex logics efficiently.
A single smart sensor system may have various functional sensors whose operating parameters are set by the microprocessor/microcontroller.
SMART SENSOR SYSTEM COMPONENTS :
The components of a smart sensor system as depicted in Fig below include sensors, power signal, communication incorporated, and signal processing typically provided by a microprocessor. One of the most significant recent advances include enabling sensor systems to function remotely on very little power. There are many examples of technological advancements in sensors, power, and communications that can enable future smart sensor systems. The ideal goal is to have a self contained system that is capable of reading data from sensor ,process and calculate associated parameters and notify using an interfacing system, all of this possible with low battery power.
SOME EXAMPLES :
An simple and real example of smart sensor systems is shown in Fig,. This family of “pocket” size gas detectors can detect and quantify several gases including hydrogen, hydrogen sulfide, carbon monoxide, and ozone with selectivity, and operate on a single small battery (used in watches) for a year or more. These systems are specifically designed to be low-cost, low-power, and have a long battery life. Included within the systems are loud alarms, a digital display, as well as computed features such as temperature compensated signals, time-weighted average dosimetry, data/event logging, and a wireless data download capability in a package weighing less than one ounce. Being able to integrate all of this within a single package is only possible through the integration of sensor and microprocessor technology and the limiting factor on battery life is typically how often the alarms are enabled, i.e., the sensing for these target analytes takes only micro-watts of power.
A second example of a smart sensor system is the “Lick and Stick” leak sensor system. This is a multifunctional system with a microsensor array fabricated by microfabrication (MEMS) based technology engineered and designed to detect hazardous conditions due to fuel leaks. The whole system posses only three sensors, signal conditioning electronics, power, data storage, calibration tables, built-in self-test, telemetry, and an option for self-power in the surface area comparable to a postage stamp.
The approach is to be able to place sensors in a vehicle, like postage stamps, where they are needed without rewiring or drawing power from the vehicle. The electronics can be programmed to provide the user with certain information required on a regular basis, but much further diagnostic information when needed. The ability to have one “Lick and Stick” sensor system send data by telemetry, as well as have several “Lick and Stick” sensor systems sending data to a central processing hub, has been demonstrated. Smart sensors systems using this “Lick and Stick” system as a core have been adapted to applications as broad as fire detection, breath monitoring, environmental monitoring, and operation on rocket engine test stands.