Abstract
In many occasions, it is very important to get the value of temperature and humidity correctly and rapidly. In recetrt years, the field of temperature and humidity's measurement and control (T&H's M&C) is developed quickly arid the chips of T&H's M&C gradually enter the life of people and will be widely used in industry and agriculture.
In allusion to the direction of this field, we develop a mixed signal, digital chip,which has abilities to measure and control both temperature and humidity. A modified schmitt trigger based relaxation oscillator is used to convert thermistor and hygrometer resistances into a frequency signal .By the way of the same time sampling and data in a ROM(Read Only Memory), the schmitt trigger frequency can be mapped onto temperature and humidity. And then a general control module accomplish the control performance. And an EEPROM is used to store the setting value during controlling.
An extensive analysis of various errors in temperature and humidity measurement is provided, We design it using VHDL language and finally software simulation using Xilinx Foundation arid hardware emulation using Xilinx XC40110 FPGA are also presented. Using EDA tools such as Synopsis and Cadence to realize it into ASIC. We synthesis this circuit with library cell of Huajing,Wuxi with 0.6um. After post-layout simulation, we taped it out and then test it using our PCB board with the good result.
The chip can measure temperature to an accuracy of 1 in the range of 0 to 99, while humidity to an accuracy of 10%RH in the range of 50%RH to 90%RH. And after setting the value of max and min of T&H, it can realize the control of caiefaction/refrigeration or dryness/wetness.
Keywords: Temperature and humidity's measurement and control (T&H'M&C), Sensor, CPLD Emulation, ASIC Realization, Intellectualized Control