Describe The Construction Of A Thermopile ?
A thermopile is a sensitive instrument used for detection of heat radiation and measurement of their intensity. It is based upon see beck effect. A thermopile consists of a number of thermocouples of Sb –Bi all connected in series. One set of junctions on one side is coated with lamp black. The other set of junctions on the other side is well polished. The arrangement is enclosed in a funnel or horn shaped vassal. The two ends T1 and T2 of the thermopile are connected to a sensitive galvanometer. Heat radiations coming from the funnel shaped side of the vessel are made to fall on the set of junctions coated with lampblack. These are absorbed and consequently the temperature of all the junctions in this set is raised. The other set of junctions being polished reflect these radiations and remain cold. Thermo is developed in each thermocouple. As thermocouples are connected in series, the thermoelectric current in each flow is in the same junction. The total current is therefore large and produces deflection in the galvanometer.The deflection in the galvanometer indicates the existences of heat radiations. The deflection is calibrated to measure directly the intensity of heat radiations. This instrument is so sensitive that it can detect heat radiations from match stick lighted at a distance of 50 meters from the thermopile.
