The tinyPFA is a Phase Frequency Analyzer, it is a portable, battery operated, two input device with a 4 inch display that can measure very precise frequency and phase differences between the signals applied to both inputs. The input frequency can be any frequency between 1 MHz and 100 MHz. Typical use is to measure the differences between two 10 MHz clocks. The tinyPFA can numerically display the phase and frequency difference, show the measurement in a graph versus time, store the measurements on a SD card inserted into a SD card slot, or send the phase measurements over USB to a program such as TimeLab for further display and processing. Phase and Frequency measurement accuracy is better then 1e-12 divided by the measurement time in seconds with decimation set to 1 Be aware the maximum frequency difference that can be displayed depends on the measurement time (Tau) and is approximately 200 / (Tau in s) so for Tau is 1 s it is 200 Hz maximum difference.