A solenoid-operated valve with DC resistance of about 10.3 Ωwas exposed to 50 % RH, its rated temperature of 80 °C, and powered at its rated voltage of 12 VDC. (Note: the valve was unrated with regards to relative humidity, RH.) Using Fourier transform infrared (FTIR) spectroscopy, the insulation material was found to be a combination of polystyrene and polyethylene terephthalate. The wire gauge was not disclosed in the valve information sheet. The conductor diameter was measured to be about 380μm and the insulation thickness was measured to be about 27μm, hence, the magnet wire size was determined to be AWG (American wire gauge) 26.5.Once every 48 hours, the valve was removed from the chamber to perform impedance measurements. The coil was at an elevated temperature when removed from the chamber, so, in order to achieve approximately isothermal impedance measurements, the settling of coil DC resistance to a constant value was used to indicate when the coil had cooled to room temperature (between 22 °C and 26 °C).Using an Agilent 16047E four-terminal fixture, the coil was connected to an Agilent E4980A LCR meter, which can measure impedance at frequencies ranging from 20 Hz to 2MHz. The LCR meter measured coil impedance at frequencies over the entire operational range of the LCR meter, with an RMS voltage of 500 mV.