Performance of the Single Junction Thermal Voltage Converter at MHz via Equivalent Circuit Simulation

The physical structure of the single junction thermal voltage converter (SJTVC) can be represented in simulation using an equivalent RLC circuit to investigate the performance and estimate the error sources. This paper describes instruments and techniques that apply 0.6 V thermal converters to achieve this aim. The technique was performed in the department of electrical metrology, National Institute for Standard (NIS), Egypt, to investigate the frequency-dependence of the SJTVC at high frequency. The LTspice/SwCAD III simulator was used to analyze the effect of the physical structure of an SJTVC in an effort to better understand the origin of errors at 100 kHz and 1 MHz. The practical results were first measured at the National Institute for Standard and Technology (NIST), U.S. to validate the simulation model at 100 kHz. The model was then used to estimate the AC-DC transfer error of the SJTVC at 1 MHz. Some of the main 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.