Thermoelectric Power Measurement System Based On VEE

This paper presents a method, which is based on complete software design, for measurement of thermoelectric materials. Thermoelectric power measurement of materials is of great significance for the study of thermoelectric materials. Thermoelectric materials are functional materials that can achieve a direct conversion between thermal and electrical energy. Devices using thermoelectric materials have outstanding advantages of small size, no noise, no pollution, no moving parts and maintenance-free, and have attractive prospect in the application of thermoelectric cooling and generation.The set of thermoelectric power measurement system in this paper is based on VEE (Visual Engineering Environment) and improves its development on the basis of thermoelectric power measurement module in the original PPMS (Physical Property Measurement System). On the PPMS hardware platform, the improved measurement system has redesigned the thermoelectric power measurement system by using the Agilent34420A digital multimeter and Agilent GPIB82357B data acquisition card. The principles and methods of the improved thermoelectric power measurement system are different from those of the original system. The improved measurement system adopts gold iron alloy wires and Ni-Au measurement lines, uses Agilent34420A to measure the temperature difference of the two loops, which are formed by measuring lines and samples, and the electric potential at both ends of material, then derives the material’s thermoelectric power value according to software calculation.The software control part is designed on Agilent VEE of Agilent Corporation. Agilent VEE is graphical programming software, which can easily control the hardware and has a highly scalable program. The software control part mainly achieves three functions:measuring control of instrument, complete data transmission and processing of the results. The measurement part mainly consists of controlling Agilent34420A to measure potential difference and controlling PPMS to measure temperature difference. GPIB protocol, utilized for data transmission, can achieve communication between instruments and VEE software. The final results are dealt with by the use of VEE’s data display and data storage.The technologies adopted and functions achieved in this paper are as follows:1. Direct I/O control and panel drive control are two ways to control instruments in VEE, for the vast majority of instruments in the industrial control. Both methods can achieve the most direct and fastest connection between the programming software and hardware equipments, with simple operation and good stability.2. GPIB communication is used to accomplish the unified control of a lot of instruments. Nowadays, GPIB is a mainstream parallel bus of the instrumentation, test systems and computer interconnection. GPIB interface, with convenient programming, reduces the burden of software design and meets the systematic demands of self-diagnosis and self-calibration. In addition, through the GPIB interface, we can connect multiple instruments to form a larger control system.3. ActiveX controls and Visual Basic Script programming are introduced to complete the data exchanges among different programming languages. ActiveX controls are reusable software components, by which we can add special features in the websites, desktop applications and development tools quickly. Visual Basic Script programming can achieve data exchanges between the VEE and other programming languages effectively, and complete a lot of special features.The results of software simulation show that the thermoelectric power measurement system designed in this paper can complete materials’thermoelectric power measurement. Compared with the original PPMS measurement system, this system can be used alone as a thermoelectric power measurement module, which improves the inadequacies of the original PPMS thermoelectric power measurement module effectively.