Optimized design and process for making a DC voltage reference based on MEMS
A micromechanical moving plate capacitor has been designed and fabricated for use as a dc voltage reference. The reference is based on the characteristic pull-in property of a capacitive microelectromechanical system (MEMS) component. The design is optimized for stability. A new silicon-on-insulator (SOI) process has been developed to manufacture the component. We also report on improved feedback electronics and the latest measurement results.
Measurement uncertainty in the presence of low-frequency noise
We discuss the measurement uncertainty in the presence of different types of fundamental noise processes, especially 1/ noise. The treatment is based on the Allan variance of an -sample average with two deadtime parameters relevant in metrology. Some results applicable to situations that are common in metrology, e.g., international comparisons, are derived. Experimentally, the output of Zener voltage standards in the frequency range from 10 6 Hz to 10 Hz is studied and behavior closely resembling that of 1/ noise is found at all time scales of practical interest. The noise floor of a 10 V Zener standard was found to be 60 nV and the 1/ corner frequency 3.5 Hz. Environmental variations cause the long-term ( 100 s) deviations of the Zener voltage to slightly increase from the limiting 1/ noise level.
Using Activity Theory in Developing Instructial Tools for Project Management Studies
Competence and skills of the project manager are significant to project success. The skills needed in project managersâ work cannot be learned only by reading the books or a lecture hall; one learns them by practice. Therefore, an important challenge for educational institutions is to develop pedagogical practices that allow students to participate in working life projects and to confront real-life problems. Project-based learning (PBL) offers a model that enables students to practice the skills and competences needed in working life projects by utilizing real-world work assignments in time-limited projects. Using PBL method alone does not necessarily guarantee learning result. In order to be successful, PBL method requires effective and competent supervision and guidance of students as well as appropriate tools for instruction. In this study the concepts from activity theory (AT) are applied to development tools for supervising project-based learning.