  Microelectromechanical systems (MEMS) can offer a competitive alternative for
conventional technology in electrical precision measurements. This article
summarises recent work in development of MEMS solutions for electrical
metrology. MEMS-based voltage references, RMS-to-DC converters, high frequency
power sensors, and reference oscillators are discussed. The main principle of
operation of the components is the balance between electrical forces and
mechanical spring forces in micromachined silicon structures. In RMS sensors
and RMS-to-DC converters, the quadratic voltage dependence of the force between
plates of a moving-plate capacitor is utilised, and the operation of the MEMS
voltage reference is based on the pull-in phenomenon of a moving-plate
capacitor. Advantages of MEMS devices compared to more conventional solutions
include small size, low power consumption, low price in mass production, and
stability. The drift caused by electrostatic charging effects has turned out to
be a major problem. This problem has not yet been solved in DC applications,
but it can be circumvented by using AC actuation instead of DC and by
compensating the internal DC voltages of the component. In this way, an AC
voltage reference with relative drift rate below 2 ppm during a three-week test
period has been constructed. Even better stability has been demonstrated with a
MEMS-based reference oscillator: no changes in resonance frequency were
observed at relative uncertainty level of about 0.01 ppm in a measurement which
was continued for more than a month. MEMS components have also been developed
for measuring RF and microwave power up to frequencies of about 40 GHz. Unlike
conventional high frequency power sensors, which measure the absorbed power,
the MEMS device measures the power that is transmitted through the sensor.
