Research On Thermal Quartz Tuning Fork Temperature Sensor

Infrared temperature sensor is mainly dependent on infrared technology toexecute temperature measurement. For many transformations and developments,it has higher precision and has been optimized to measure the maximum tempera-ture change upon exposure to the measurand. These are attributable to two fac-tors:(ⅰ)development and integration of the existing thermo-sensitive materialwith large and repeatable temperature coefficient of the property being used asthe measurement principle,and(ⅱ) development of sensing structures capable ofrealizing a maximum temperature change upon exposure minimum amount ofinput. The second requirement implicitly constrains thermal sensors into the mi-cro and nanoscale sizes where the thermal mass of the system is extremely smalland therefore small amounts of absorbed power results in large changes in tem-perature. So by use of the latest principle, material, the sensor can become moreresistant to interference, more stable, low power and cost.A low-cost and high sensitive thermal quartz tuning fork temperature sensorbased on a quartz tuning fork resonator was developed. The mechanical resonatorused was a common commercially available quartz tuning fork modified with apolymer wire (made by PNIPAAm).The role of the polymer wire is to provide aninfrared or temperature sensitive element to the otherwise relatively temperatureinsensitive tuning fork. Firstly, the paper introduces the piezoelectric effect andvibration mode of quartz crystal and chooses a specific cut by comparing the fre-quency-temperature characteristic of various quartz crystal cuts. Then the shapememory theory of PNIPAAm was analyzed and the polymer wire sensitive ele-ment with high temperature sensitivity was obtained. After selecting the appro-priate crystal, the polymer wire quartz tuning fork temperature sensor was de-signed. Secondly, the whole hardware structure is set up: the paper designs a kindof crystal oscillation circuit working under the subthreshold and differential fre- quency circuit with D flip-flop. The two circuits have been experimentally testedto prove their stability. Lastly, the overall experimental system is established. Thepaper represents the static and dynamic characteristics of the sensor to obtain thethird-order equation of the frequency-temperature and thermal response time, andthen summarizes the error factors.