Thousands of everyday appliances utilize pressure sensors, although they are not used directly in all these devices and are often indirectly used in the measurement of fluid/gas flow, speed, water level and altitude. Pressure sensors are among the most widely used electronic sensors and are manufactured by more than 300 companies worldwide. There are at least 50 different technological methods, all varying in design, performance rating, efficiency, cost and output method. Advanced pressure sensors include the dynamic sensor category, where very high speed changes in pressure are measured, and they are manufactured from non-conventional materials such as quartz. Some pressure sensors, such as those used in industry, act as a binary switch.