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Applications Note 1-3result in a perceived signal 3.38% less than the true open circuit voltage the strain bridge wouldotherwise provide. Although the zero hertz case is useful to consider, most measurement systemsare required to measure dynamically changing inputs. In this case, equation 1-1 isextended to encompass the dynamic case by replacing resistances with impedances Z output andZ instrument .It is equally important to be aware that energy will be exchanged between the sensor and theenvironment in many different forms and via many different paths where all forms and paths ofenergy ßow must be considered for valid information to result.4. All sensors respond to all inputs; it is simply a matter of the degree of the response. If our goalis to design an accelerometer, we would, of course, set out to design the device so that it is notinfluenced by temperature, pressure, rate of temperature change, humidity, substrate strain, radiation,transverse acceleration inputs, and a host of other possible characteristics of the environment.In reality, this is not achievable. The physical constraints of having to fabricate sensorstructures with imperfect materials, having imperfectly-toleranced subcomponent parts and inusing less-than-perfect transduction methods, means that we must carefully design the sensorwith these shortcomings in mind.5. As the information provided by a sensor is conducted, conveyed, transformed into other energyforms, or interpreted, it is degraded at every opportunity. The random content of any organizedform of energy will increase at any and all opportunities. The act of amplifying a sensor signalwill undoubtedly increase the magnitude of the perceived signal but will likewise increase thepercentage of randomness or noise that is present in the amplified signal. In many ways, the tendencytowards randomness may be likened to the thermodynamic property of entropy which isthe irreversible tendency of a system or the universe toward increasing disorder.The focus of the instrument engineer is to be aware of the consequences of thepresence of the sensor within a system, to minimize the influence that the sensorwill have on the measured phenomena as well as being aware of the influence ofother aspects of the environment on the quality of the information that the sensorprovides.It is the sensor that is the source of information upon which aerodynamicists makedesign modifications, how an old bridge is buttressed, or whether the air bag in ourautomobile should initiate. It is the quality of this information that will establishour success, or in some cases, our very survivability. The strain-based sensor, themost prevalent sensor type in the world today, is the focus of the following dissertation.The Art of Practical and Precise Strain Based Measurement 2nd Edition © 1999 CHAPTER 1-11