Sensors are used with a computer to measure physical aspects of the world around us such as temperature, light intensity, velocity, air pressure, and pH. A transducer is used in the device to convert the physical phenomena to an electrical current or voltage. The electrical signal is then converted to a number by electrical circuitry called an analog interface and communicated to the computer. The analog interface can be a separate piece of equipment in between the sensor and the computer or it can be built into either the sensor or the computer.