Ultrasonic Measurement uses sound waves to interrogate the fluid or object and determine various key properties. The sound waves are typically sent and received by a piezo electric transducer which converts electric signals to pressure waves and vice versa. Ultrasound spectrum includes wave frequencies from 20kHz to several gigahertz depending on the application. For example, for flowmeters, the range is typically 50kHz-2Mhz. In most flowmeters, the ultrasonic signals are typically used to precisely measure downstream and upstream transit time in a pipe. Transit time is then converted to a flow rate. The transit time also allows accurate determination of the gas sound speed, which in turn enables further properties to be calculated such as molecular weight.