Introduction to Sensors

Introduction to Sensors

Sensors are devices that are used to measure physical variables like temperature, pH, velocity, rotational rate, flow rate, pressure and many others. Today, most sensors do not indicate a reading on an analog scale (like a thermometer), but, rather, they produce a voltage or a digital signal that is indicative of the physical variable they measure. Those signals are often imported into computer programs, stored in files, plotted on computers and analyzed to death.

Sensors come in many kinds and shapes to measure all kinds of physical variables. However, many sensors have some sort of voltage output. There are a number of implications to that.

·        If a sensor has a voltage output, then it is a voltage source that is controlled by the physical variable it measures.

·        If the sensor is a voltage source, you need to remember that no physical voltage sources are  ideal, and non-ideal voltage sources are usually best described with a  Thevinin  Equivalent Circuit that contains the voltage source and an internal resistance.

·        If a source has an internal resistance, there is a possibility of loading the source. If a significant load is attached to the source, the terminal voltage will drop. At that point, the terminal voltage is not what you expect it to be (from calibrations, spec sheets, etc.)

Need of Sensors

Seismic monitors provide an early warning system for earthquakes.

The latest sensor equipment includes heart rate, electrical voltage, gas, light, sound, temperature, and distance sensors. Data is collected via the sensors and then transmitted to the computer. Up to date software is used to collect, display and store the experimental data. The computer software can then display this data in different formats - such as graphs, tables or meter readings, which make it easy for students to understand the process and bring science to life.

The significance of sensor technology is constantly growing. Sensors allow us to monitor our surroundings in ways we could barely imagine a few years ago. New sensor applications are being identified everyday which broadens the scope of the technology and expands its impact on everyday life.

In Industry

On the factory floor, networked vibration sensors warn that a bearing is beginning to fail. Mechanics schedule overnight maintenance, preventing an expensive unplanned shutdown. Inside a refrigerated grocery truck, temperature and humidity sensors monitor individual containers, reducing spoilage in fragile fish or produce.

In the Environment

Networks of wireless humidity sensors monitor fire danger in remote forests. Nitrate sensors detect industrial and agricultural runoff in rivers, streams and wells, while distributed seismic monitors provide an early warning system for earthquakes. Meanwhile built-in stress sensors report on the structural integrity of bridges, buildings and roadways, and other man-made structures.

For Safety and Security

Fire fighters scatter wireless sensors throughout a burning building to map hot spots and flare-ups. Simultaneously, the sensors provide an emergency communications network.

Miniature chemical and biological sensors in hospitals, post offices, and transportation centres raise an alarm at the first sign of anthrax, smallpox or other terror agents.