The name Radiometer is frequently used to refer to a Crookes radiometer ("light-mill"). This is an early device wherein a rotor in a partial vacuum spins when exposed to light.
The Nichols radiometer is a newer and more sensitive radiometer than the Crookes type. It measures radiation pressure. It has two small mirrors suspended on a quartz fiber.
A microwave radiometer operates in the microwave wavelengths. The radiometer contains argon gas to enable it to rotate.
The MEMS radiometer can operate on the same principles of Nichols or Crooke radiometers. It can operate over a wide spectrum of wavelength and particle energy levels.