1. A process variable transmitter for coupling to a process and providing an indication of a variable of the process over a communication bus, the process variable transmitter comprising: a process variable sensor coupleable to the process to provide an analog indication of the variable; an analog-to-digital converter coupled to the process variable sensor and providing digital information indicative of the analog indication provided by the sensor and providing digital bitstream information; output circuitry configured to provide an output related to the process variable; a microprocessor system coupled to the analog-to-digital converter and configured to calculate power spectral density of the digital bitstream information using a Hanning window size of 65536 samples and responsively generate diagnostic information based on the power spectral density; wherein the digital information includes the digital bitstream information data having a frequency in excess of about 55 kHz; and wherein the digital bitstream information is transferred to the frequency domain using a Fast Fourier Transform (FFT).