Understanding Smart Sensors - Nomads.usp

62 Understanding Smart SensorsTable 3.1Common Undesirable Characteristics of Semiconductor Sensors (After: [15])Characteristic Sensor Design Sensor Interface MCU/DSPNonlinearity Consistent ReduceDrift Minimize CompensateOffset Calibrate Calibrate/reduceTime dependence of MinimizeAuto-zerooffsetTime dependence ofAuto-rangesensitivityNonrepeatabilityReduceCross-sensitivity toCalibrateStore value and correcttemperature and strainHysteresisPredictableLow resolution Increase AmplifyLow sensitivity Increase AmplifyUnsuitable outputBufferimpedanceSelf-heating Increase Z PWM techniqueUnsuitable frequency ModifyFilterresponseTemperature dependenceStore value and correctof offsetTemperature dependenceStore value and correctofsensitivityperformance can result when the design of the sensor and the capability of subsequentcomponents that achieve a smart sensor are taken into account in theoverall design of the smart sensor. Digital logic provided by either an MCUor a DSP plays a vital role in smart sensing and in improving the sensor’sperformance.3.4 Digital Output SensorsA sensor that directly interfaces to an MCU without requiring A/D conversionsimplifies system design and reduces the cost of the MCU. Today’s sensors