Real time signal validation circuitry for burst-type laser velocimeters

The laser velocimeter (LV) is often used to measure the velocity of fluid flows. Burst-type signal processing is one of the more popular methods of extracting velocity information from randomly occurring LV signals. A major assumption in burst-type signal processing is that each LV signal processed is the result of an individual particle which is following the flow. Before accepting a measurement, burst-type LV processors perform various signal validation tests which determine if an LV signal satisfies the above assumption. These signal validation tests are either performed during data acquisition (at the expense of a minimal data acquisition cycle time) or after data acquisition has ended (at the expense of efficient data acquisition memory use). Circuitry was designed which performs a signal validation test in real time, thereby making efficient use of data acquisition memory at no cost in time to the data acquisition cycle. A system was designed to simulate LV signals so that the signal validation circuitry could be compared to another method of hardware signal validation under controlled and repeatable conditions. Results are presented from tests made by processing these simulated LV signals. Results are also presented from tests made by processing real LV signals. These results show that the signal validation circuitry consistently improves the quality of the data acquired by the LV processor. The most substantial improvement in the data quality is observed when processing signals with a low signal-to-noise ratio.