Any instrumentation system can be described as having three fundamental components: a sensor, a signal

processor, and a display and/or storage device. Although all these components of the instrumentation system

are important, the sensor serves a special function in that it interfaces the instrument with the system being

measured. In the case of biomedical instrumentation, a biomedical sensor (which in some cases may be referred

to as a biosensor) is the interface between the electronic instrument and the biological system. There are some

general concerns that are important for any sensor in an instrumentation system regarding its ability to

effectively carry out the interface function. These concerns are especially important for biomedical sensors

because the sensor can affect the system being measured and the system can affect the sensor. Sensors must be

designed so that they minimize their interaction with the biological host. It is important that the presence of the

sensor does not affect the variable being measured in the vicinity of the sensor via interaction between the sensor

and the biologic system. If the sensor is placed in a living organism, that organismwill probably recognize it as a

foreign body and react to it. This may change the quantity being sensed in the vicinity of the sensor so that the

measurement reflects a reaction to the foreign body rather than a central characteristic of the host.