Spine Fit

A hot object placed in a colder flowing medium is cooled by thermal convection. This principle is applied in this method. Here the rate of cooling is proportional to the rate of flow of the medium. A thermistor placed on the blood stream is kept at a constant temperature by a servo system. The rate of flow can be determined by the electrical energy required to maintain the constant temperature of the thermistor. In another method an electric heater is placed between the two thermocouples, which are located by some distance apart along the axis of blood vessel. The blood velocity can be determined by the difference between the upstream and downstream temperature indicated by the sensor. Since it is oldest method of blood flow determination, it is replaced by the radio-graphic technique.