Performing Synchronized Vibration and Temperature Measurements
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| Many applications require the functionality of both Dynamic Signal Acquisition (DSA) and Data Acquisition (DAQ) devices. One example is the acquisition of both vibration and temperature measurements. An NI Dynamic Signal Acquisition device (PXI-4472) can be used to acquire the vibration data from accelerometers, and an NI Multifunction Data Acquisition device (PXI-6052E), with Signal Conditioning hardware (SCXI-1102), can be used to acquire the temperature data from thermocouples. It is imperative that the acquired vibration and temperature data is synchronized. Otherwise, the two measurements are difficult to compare and analyze. Numerous synchronization techniques exist for systems containing both DSA and DAQ devices. In the case of a system comprised of a PXI-4472 and a PXI-6052E, the synchronization is achieved by routing the PXI-4472's oversample clock to the PXI Star Trigger Line. The oversample clock is a timing signal required by the PXI-4472's delta-sigma converters. It is shared over the PXI Star Trigger Line at 256 or 128 times the sample rate of the PXI-4472. One of the PXI-6052E's general purpose counters can then be used to divide this signal down to a selected rate. The counter's output is routed over one of the PXI Trigger Lines and used as the sample clock for the PXI-6052E. Because the divide-down ratio can be any integer number of two or greater, the PXI-4472 and PXI-6052E can sample at different rates while maintaining synchronization. Finally, to guarantee that both the PXI-4472 and PXI-6052E begin acquiring at the same moment, the PXI-4472's start trigger is routed over one of the PXI Trigger Lines and used by the PXI-6052E as its start trigger. |
This synchronization technique also allows for multiple PXI-4472s and PXI-6052Es to be synchronized. Additional PXI-4472s can achieve synchronization by using the oversample clock available on the PXI Star Trigger Line. Furthermore, multiple PXI-6052Es can divide down the oversample clock with one of their general purpose counters to obtain their sample clock or use the sample clock that is available on one of the PXI Trigger Lines.
Figure 1: Front Panel of DSA and DAQ Synchronization VI
Related Links:
PXI 4472 and MIO Analog Input Synchronization
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