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

This research investigates the potential of using a microwave disk 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 current (ac) voltages. The use of a disk 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 disk resistor. The results indicate that the disk 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 disk resistor, because of its residual parameters, significantly increased the ac-dc transfer difference from 707 to $2241~\mu $ V/V and its expanded uncertainty from 298 to $1367~\mu $ V/V at 100 MHz compared to the CTVC with a microwave rod resistor.