Editing Humidity Detector Based on Quartz Crystal Oscillator (section)

== Results and Discussion ==
=== Building Colpitts oscillator circuit ===
A Colpitts oscillator circuit was successfully constructed on a breadboard, and stable oscillation was achieved. The designed oscillation frequency was approximately 6 MHz. For the uncoated quartz crystal, the measured oscillation frequency was 5.9786 MHz, which is consistent with the expected value within experimental uncertainty.
[[File:Circuit.jpeg|500px|thumb|center|Colpitts oscillator circuit on breadboard]]
[[File:5271-1.jpg|500px|thumb|center|Waveform Diagram without coating]]

=== Sustainability Test ===
After film deposition, the stability of the oscillator was evaluated under different environmental conditions. Measurements were conducted in a laboratory environment (22 °C, ~40% relative humidity) and an outdoor environment (30 °C, ~75% relative humidity). In both cases, the oscillator was operated continuously for approximately one hour, during which stable oscillation with negligible frequency drift was observed, indicating good operational stability.
[[File:Out-of-room-testing.jpeg|500px|thumb|center|Outdoor environment testing]]

=== Humidity Sensing Performance ===
The humidity sensing performance was then investigated. Due to the lack of a calibrated humidity chamber, a qualitative humidity variation was introduced by placing different volumes of deionized (DI) water inside a sealed test tube then place the crystal on the top of it. The oscillator frequency was monitored under these conditions. Given that the relative frequency shift is small compared to the absolute frequency (~6 MHz), the frequency was estimated by recording the waveform over a 1-second interval and counting the number of oscillation cycles.
The results show a clear dependence of oscillation frequency on the amount of water present. Starting from 10 mL of DI water, The oscillate frequency of the origin crystal in lab environment is 5.981744 MHz, which is the same as when placed at the top of the sealed test tube with 10 mL of DI water. Every additional 10 mL led to an approximate frequency decrease of 25 Hz, when in 20mL, the frequency is 5.981719 MHz; when in 30mL, the frequency is 5.981694 MHz. This trend indicates that the system is sensitive to humidity-induced changes.
[[File:F-Vgraph.png|500px|thumb|center|Frequency-Volume Curve]]