Editing Humidity Detector Based on Quartz Crystal Oscillator (section)

===Experimental Setup and Measurement Procedure ===
*'''Humidity Sensing Testing:''' Due to the absence of a calibrated humidity chamber, qualitative humidity variations were simulated using a sealed test tube setup. The coated crystal was placed at the top of the test tube. To create environments with increasing moisture, DI water was sequentially added into the test tube in volumes of 10 mL, 20 mL, and 30 mL.

*'''Data Acquisition:''' Because the humidity-induced frequency shift is minute (typically on the order of tens of hertz) relative to the 6 MHz absolute baseline, a high-precision counting method was employed. The output signal from the buffer stage (OUT) was fed into a digital oscilloscope. The oscillation frequency was estimated by recording the waveform over a precise 1-second interval and counting the total number of oscillation cycles within this gate time. Before introducing any moisture, an initial baseline frequency of the dry coated crystal was recorded. Measurements were then taken for each incremental volume of DI water. To minimize random measurement errors and noise fluctuations, the frequency was monitored until the reading stabilized, and this steady-state value was recorded as the final data point for that specific humidity level.