SENSITIVITY COMPARISON OF ACOUSTIC THERMOMETERS OF DIFFERENT TYPES

Fundamental parameters of acoustic thermometers (AT) with a piezotrans ducer (PT) without coupling layers and with a quarter-wavelength coupl ing layer, i.e., the noise temperature T(n) and the equivalent transmi ssion band DELTAf(e) and also the value of AT threshold sensitivity th eta determined by them, are found out in the basis of data obtained in Ref. 4. Taking into account real values of AT parameters (losses in P T without a quarter-wavelength coupling layer, high frequency amplifie r noise, utilization of a modulator and a square-law detector) the cal culated value of theta is about 0.4 K, which is considerably higher th an the value of theta = 0.05 K obtained in Ref. 2 without taking accou nt of these parameters. The value of theta can be reduced to 0.1 K for PT with a quarter-wavelength coupling layer.