Photometer is an instrument for comparing the luminous intensity of the sources of light.
Planimeter is a mechanical integrating instrument to measure area of a plane surface.
Pyknometer is an instrument used to measure the density and co-efficient of expansion of liquid.
Pyrheliometer is an instrument for measuring solar radiations.
Pyrometers are thermometers to measure high temperatures.
Quadrant is an instrument for measuring altitudes and angles in navigation and astronomy.
Quartz clock is a highly accurate clock used in astronomical observations and other precision work.
Radar (acronym of radio detection and ranging) is used for detecting and finding the range of moving objects by transmitting beams of radio waves.
Radio Micrometer is an instrument for measuring heat radiations.
Rain Gauge is an instrument for measuring rainfall.
Rectifier is a device that passes current only in the forward direction and can be used as AC to DC convertor.
Refractometer is an instrument used to measure the refractive index of a substance.
Repeater is a device that receives signals in one circuit and automatically delivers corresponding signals to one or more circuits.
Resistance Thermometer is used for determining the electrical resistance of conductor.
