New Generation of Crystal Quartz Thin-Film Multijunction Thermal Converters
The design of a new generation of planar multijunction thermal converters (PMJTCs) on quartz membranes and on quartz crystal chips improves the frequency response of the PMJTC in the frequency range from 100 kHz to 100 MHz and allows a decrease in the uncertainties. For a heater resistance of 1 kOmega ac-dc voltage transfer differences smaller than 5 muV/V are calculated for frequencies above 100 kHz up to 1 MHz. This is a reduction of more than one order of magnitude in the ac-dc voltage transfer differences for such high heater resistance in comparison to the PMJTCs with Si3N4/SiO2/Si3N4 sandwich membrane on a silicon chip. The quartz PMJTCs allow the improvement of the standard uncertainties to 3 muV/V in the frequency range of 100-500 kHz and 5 muV/V for 700 kHz to 1 MHz. The model for calculating the ac-dc voltage transfer differences and the uncertainty budget are given
AC-DC-mV-transfer with highly sensitive thin-film multijunction thermal converters
Bismuth-antimony thermocouples are discussed, and the responsivity of the thin-film multijunction thermal converter is improved to 16 VW/sup -1/ in air and 120 VW/sup -1/ in vacuum. With these converters the AC-DC voltage transfer is extended into the mV range. >
Fast thin-film isothermal ac-dc converter with radiometric sensing
A dual heater isothermal converter for precise ac-dc transfer is realized by using thin-film heaters on a thin dielectric membrane, and by sensing their temperature with an infrared pyrometer or a thin-film infrared sensor. This reduces diversion of thermal energy from the heaters, as well as reducing the thermal time constant and the ac-dc transfer differences due to thermoelectric effects, shunt capacitances and dielectric losses. >