Airborne Systems

A wide variety of sensors (also known as transducers) are used to measure and acquire a physical property’s value. It is up to the instrumentation engineer to select the device to meet the environmental, response, accuracy, size, and cost specifications for the application. Signal conditioners serve as the interface of the data acquisition system from the transducers. Many transducers require ac or dc power (e.g., thermistors, strain gages, and linear variable differential transformers - LVDTs) while others generate signals (tachometers, thermocouples, and piezoelectric strain gages). They provide excitation (power), network calibration, signal amplification, and filtering.

In airborne data acquisition, sensor output characteristics must be transformed, filtered, or modified for compatibility with the next stage of the system. The absolute relationship between the output and the actual property value of the measurand may vary with time, altitude, pressure, temperature, etc. Therefore, signal conditioners also incorporate calibration features to assist in defining the relationships.

A system under test may be subjected to known physical characteristics and the output measured to ascertain and verify the relationship between the sensor and its output. For example, when on the ground, an airplane’s flaps may be moved at known angles, while measurements are taken on sensor or airborne system output. The plot of angle vs. output will be used by the ground system for real-time data display in engineering units.

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