This paper presents a detailed analysis of the accuracy of nonoscillating one-port device noise measurements. A new expression is given for the calculation of the noise temperature from parameters that can be measured directly by using either a power sensor or a noise meter with the capability of making power measurements. A general expression for the DUT noise temperature error function is also obtained, which enables the authors to study how the noise measurement accuracy is affected by a number of different factors. This expression has been found very useful in order to study how the accuracy can be improved in a given noise measurement system. The error function has been applied to evaluate the uncertainty of Schottky barrier device noise measurements.>