The linearity of a transistor amplifier comprising a plurality of transistors operating parallel is improved by reducing the odd order transconductance derivatives of signals generated by the transistors. In a described embodiment, a method of sensing multiple parameters is provided in which an interferometric fiber optic sensor is connected to a variable wavelength light source. In addition, the corrosion inhibitor provides for the attenuation of a signal used during radiography interrogation thereby providing for detection of anomalies on the surface of the substrate. The data portion of the message includes an op-code that dictates various other elements that form part of the message. The process substantially increases the net yield of iodixanol and simplifies its purification.