Construction and measurement examples of a wireless sampling-synchronized measurement system.

摘要

We have developed a portable wireless sampling-synchronized measurement system that can provides accuracy to within one micro-second. Our systems use radio waves from wireless LAN access points to synchronize all analog to digital converters of different amplifier units making it possible to measure transfer functions at different points. This is especially useful in environments such as buildings and automobiles where measurements from both sides of glass walls or windows are required allowing measurements of transfer function and propagation of sound and vibration to be measured accurately. Until recently, wireless synchronized sampling was not possible due to the availability of only IEEE 1588 or wired sampling-synchronized systems. Having only start trigger functionality is insufficient when continuous synchronized sampling is required. Considering crystal oscillator units which generate clock for analog to digital converters operate independently from each other, the crystal oscillator units have to be synchronized continuously and repeatedly throughout the entire measurement time. During evaluation of the system performance, we kept the input cable lengths the same for the test signal of each unit as radio waves used for synchronization and electric current used for test signal travel 300 meters per micro-second. We introduce the system and provide some measurement examples.