Doing so requires accurate instrumentation, another area for the electrical engineer. Electrical engineers who work in this area develop electrical devices to measure quantities such as pressure, temperature, flowrate, speed, heart rate and blood pressure. Often, the electrical devices convert the measured quantity to an electrical signal that can be read by a control system or a computer. Instrumentation engineers also design systems to transmit the measured information to a recording device using telemetry. For example, such systems are needed for transmitting a satellite's measurements to the recording computers back on earth as it orbits a distant planet.
Signal processing is another area where electrical engineers are needed.
In many instances the electrical signals coming from instrumentation or other sources must be conditioned before the information can be used. Signals may need to be electronically filtered, amplified or modified. An example is the active noise control system on a stethoscope which allows a paramedic to listen to a patient's heart while in a helicopter. The active noise control system can block out the sound of the helicopter so that the paramedic can make quick, accurate assessment of the patient. Signal processing also comes into play in areas such as voice recognition for computers.