High-temperature High-precision Resistance Measurement System And The Fe <sub> 78 </ Sub> Si <sub> 9 </ Sub> B <sub> 13 </ Sub> Amorphous Alloy Crystallization Process Of The Thermoelectric Properties

According to the value of the resistance, there are a lot of methods to measure resistance. However, when measuring micro resistance, Kelvin bridge method which is used to measuring low resistance is not applicable. So we need a system to measure micro resistance. Thermocouple is generally decided to measure resistance under high temperature. The thermocouple has advantages of simple structure, wide measuring range(-180℃～1800℃),high temperature resistance, high accuracy, low cost, convenient usage, suitable for remote measurement and automatic control.When measuring resistance with high precision under high temperature, KEITHLEY 2182 NV voltmeter is used to monitoring temperature and voltage, PF66M digital millimeters is used to monitoring and providing current. Binding RS232 serial port, the communication between computer and resistance measurement system can be realized by using SPCOMM serial communication active control which is based on Delphi. In order to improve measuring accuracy, it is necessary to use four lines measuring method and reversal current chronopotentiometry. The aim of using reversal current chronopotentiometry is to eliminating the influence of thermoelectric power which is generated under resistance measurement. Electric relay is used to implementing inverse current. Current is provided by PF66M digital millimeters. Reversal current chronopotentiometry have to restrict sampling interval. To solve this problem, timing control is applied in electric relay. Timer control which is included in Delphi is used in the program. Program of controlling electric relay is executed every 4 seconds. Sampling time interval of 4 seconds can satisfy requirements of eliminating thermoelectric power.By using resistance measurement system with high precision under high temperature and acquisition system, we measure the resistance of Fe,Cu,Al under room temperature. The experimental lasted 10~12 hours. It is concluded that the system is stable according to analyzing resistance value. When measuring micro resistance, reversal current chronopotentiometry is used to eliminate the influence of thermoelectric power. In order to made comprehensive analysis on structure change of Fe78Si9B13 amorphous alloy between crystallization processes, we use converse thinking to analyze the change law of stray thermoelectric power of Fe78Si9B13 amorphous alloy between crystallization process. Moreover, we measured the thermoelectric power of thermocouple composed by Cu and Fe78Si9B13 amorphous alloy. Through analyzing, it is appeared that the stray thermoelectric power of Fe78Si9B13 amorphous alloy and contact potential of Cu and Fe78Si9B13 amorphous alloy all had mutations with the temperature increasing. The mutations are corresponding to the crystallization of Fe78Si9B13 amorphous alloy.It is necessary to smooth resistance curve or diffraction intensity when studying on liquid and amorphous state structures. MyXray is software which have powerful function on smoothing. In order to use MyXray to deal with experiment which is collected from resistance measurement system with high precision under high temperature or x-ray diffract meter, we designed a program which can change the to the format MyXray needed.