Calorimetric Thermal Voltage Converter With a Microwave Disk Resistor as a Heater

This research investigates the potential of using a microwave disc resistor as a heater in a calorimetric thermal voltage converter (CTVC). The CTVC is a highly accurate instrument for measuring the root-mean-square (RMS) value of alternating (AC) voltages. The use of a disc resistor instead of a traditional rod resistor offers several potential advantages, including a reduced thermal time constant, simplified assembly, and a more uniform temperature distribution. Numerical studies and laboratory experiments were conducted to evaluate the performance of the CTVC with a disc resistor. The results indicate that the disc resistor can serve as a viable alternative to the rod resistor, simplifying the assembly of the CTVC, reducing thermal time constant and direct current (DC) reversal error by about 10%. However, we found that the disc resistor, because of its residual parameters, significantly increased the AC–DC transfer difference from 707 μV/V to 2241 μV/V and its expanded uncertainty from 298 μV/V to 1367 μV/V at 100 MHz compared to the CTVC with a microwave rod resistor.