Sensors are devices that convert a physical parameter such as room temperature, blood pressure or wind speed into a signal that can be measured electrically. Other sensor outputs are equally valid (e.g. visual output from a glass thermometer), but we will confined our coverage to electrical output sensors as they are more compatible with electronic measuring devices.
Once the physical parameter has been converted to an electrical equivalent it is easily input into a computer or microprocessor for manipulating, analyzing and displaying.
By far the most common parameter measured is temperature. At present temperature is the only parameter covered in detail.
Each year hundreds millions of sensors are manufactured. They are in domestic appliances, medical equipment, industrial control systems, air-conditioning systems, aircraft, satellites and toys.
Sensors are becoming smarter, more accurate and cheaper. They will play an ever increasing role in just about every field imaginable.