Abstract:
Critical cold temperature is one of the most crucial control factors for crop frost protection. Tea leaf's capacitance
has a significant response to cold injury and appears as a peak response to a typical low temperature which is the
critical temperature. However, the testing system is complex and inconvenient. In view of these, a tea leaf's critical temperature detector based on capacitance measurement module was designed and developed to measure
accurately and conveniently the capacitance. Software was also designed to measure parameters, record data,
query data as well as data deletion module. The detector utilized the MSP430F149 MCU as the control core
and ILI9320TFT as the display module, and its software was compiled by IAR5.3. Capacitance measurement module was the crucial part in the overall design which was based on the principle of oscillator. Based on hardware
debugging and stability analysis of capacitance measurement module, it was found that the output voltage of the
capacitance measurement circuit is stable with 0.36% average deviation. The relationship between capacitance
and 1/Uc2 was found to be linear distribution with the determination coefficient above 0.99. The result indicated
that the output voltage of capacitance measurement module well corresponded to the change in value of the capacitance. The measurement error of the circuit was also within the required range of 0 to 100 pF which meets
the requirement of tea leaf's capacitance
