  Thermoelectric power sensors are widely used in commercial power meters at RF
and microwaves, due to their superior robustness, stability, and accuracy if
compared with other types of power sensors. Furthermore, their electrical
architecture and related performance turned out to be very useful in the
realization of the broadband primary power standards as alternative to
resistive power sensors, i.e. bolometers. Hereby we present a comparison in
term of effective efficiency of a thermoelectric sensor calibrated by applying
two different methods of power substitution when used as thermal load in a
coaxial microcalorimeter at RF and microwaves. The aim is to test a technology
that could enable the realization of a primary RF/MW power standard
independently of the assumption of unitary efficiency at the dc (or LF)
reference power.
