Performance of Single Junction Thermal Voltage Converter (SJTVC) at 1 MHz via Equivalent Electrical Circuit Simulation
The physical structure of the SJTVC can be represented via simulation using an equivalent RLC circuit to investigate the performance and estimate the error sources when using this device as a precise tool for AC voltage and current measurements. This paper describes instruments and techniques that apply on 0.6 V thermal converters to achieve this target. The technique was performed, theoretically and practically, to investigate the frequency-dependence of the SJTVC up to 1 MHz. The LTspice/SwCAD III simulator was used to analyze the effect of the physical structure of SJTVC in an effort to better understand the origin of errors at 100 kHz and 1 MHz. The practical results were firstly measured at National Institute for Standard and Technology (NIST), US to validate the simulation model at 100 kHz. The model then used to estimate the AC-DC transfer error of the SJTVC at 1 MHz. Some of the dominated error sources such as the changes of the real part of the heater impedance, the effect of thermocouple grounding and the power consumed in the internal resistance of the thermocouple are estimated at 100 kHz and 1 MHz. The expanded uncertainty assigned to the AC-DC automated calibration system of NIS is also described.
Achievement of AC Voltage Traceability and Uncertainty of NIS, Egypt through Capabilities of NIST, USA
This paper describes the methodology used to achieve the AC voltage traceability and the associated uncertainty in National Institute for Standards (NIS), Egypt via the capabilities of National Institute for Standards and Technology (NIST), USA.  The methodology includes the use of the thermal voltage converters (TVCs) and micropotentiometers (µPots) via a new automated calibration system for determination of the AC-DC Differences at different frequencies.  To confirm the results of this process, a bilateral comparison with NIST was organized through a set of (TVCs) to cover the range from 1 V to 200 V at frequencies of 55 Hz, 1 kHz, 10 kHz and 200 kHz.  The comparison results associated with the uncertainty analysis are also discussed in this paper.  For low values of AC voltage, new three µPots were fabricated at NIST to establish the traceability from 50 mV to 200 mV at frequencies from 20 Hz to 1 MHz. The converters used in this work are also modeled then simulated using LT-spice/SwCAD III simulator. Keywords: electrical measurements, thermal voltage converter, micropotentiometer, modelling and electrical simulation, uncertainty analysis, bilateral comparison.
Mathematical Time and Physical Time in the Theory Of Relativity
In the Theory of Relativity time is an imaginary quantity that can not be observed; it is a multiplication of a number that indicates duration of material change and number i that is an imaginary number. i on the square is -1. Time i⁄t is a mathematical time that describes the speed and the duration of material change. In the Universe one can observe physical time only as a stream of material change. It is not that change run in physical time, change itself is physical time.. Distinction between imaginary mathematical time and visible physical time opens some new perspectives into interpretation of Theory of Relativity. c