Pankhuri T.

There are two methods of measurement of any physical quantity: the direct method and the indirect method. In the direct method any physical quantity like length, mass, etc are measured directly by some instruments like the measuring tape, weighing scale etc. In the indirect method of measurements some device, called transducer, is used, which is coupled to the connecting apparatus that forms the part of the measuring system.The transducer selected for the measuring system is such that the output obtained is proportional to the input.It is a device which converts one form of energy to other form of energy.Example- Thermometer(The temperature of the surroundings or body cannot be measured directly, but we know that liquids tend to get expanded when heated and get contracted when cooled. This property of the liquids is used to measure the temperature in thermometers, which is type of transducer.In thermometers there is thin capillary tubing and small bulb at the bottom, which is filled with highly temperature sensitive liquid called mercury. When the temperature of the bulb of the thermometer increases, the mercury tends to expand and fill the capillary tube to certain level depending on the temperature. The thermal expansion of mercury is proportional to the temperature of the mercury, so more is the bulb temperature more is expansion of the fluid. Thus if the bulb temperature is higher, mercury will expand to higher levels in the capillary and if its temperature is lesser, the rise in level will also be lesser).