Industrial Application Case Study - Data Acquisition Non-Destructive Testing

Industrial Applications

Non-Destructive Testing (NDT) Scanning Inspection

Customer Case

The customer is testing interior of pipes with time-resolved fluorescence, a Photo Multiplier Tube (PMT), a transducer with 8 MHz BandWidth and an integration chamber. They are searching for rare events and the scan width is approximately 3.5 inches. Multiple Record: 350 scans x 3 Kpts.

GaGe Case Solution

We recommended 5X-10X over sampling - therefore CompuScope 14100, CompuScope 12100, or even the 8-bit CS8500 may be sufficient.

For a CS8500 Single Record example, say, at the single-channel sampling-rate of 50 MS/s, a 3000 point (i.e. 3 KS) acquisition would take about 60 ms (60 microseconds) to capture. To then transfer that 3 KB acquisition to PC-RAM using PCI bus-mastering (at over 100 MB/s), for display and saving, would take about 30 ms per channel. After that, a nominal 30 ms per card is required to rearm for the next trigger. So, for a one-card (i.e. one-channel) system, this gives a total cycle-time of about:

[60 ms + 1 chan * 30 ms + 1 card * 30 ms] = 120 ms

This gives a maximum repetitive-trigger Pulse Repeat Frequency (PRF) of up to 8333 Hz [1/120 ms]. Assuming that the triggers arrive at this rate, the measurement coverage is about 50% since it takes 60 ms to capture the signal, and 60 ms for transfer and rearm.

Therefore, Single Record mode provides acquisition coverage of 60 ms out of every 120 ms, <50%.

In Multiple Record mode of operation, the rearm interval time between each acquisition record is reduced down to less than 20 sampling-clock cycles (e.g. giving only 400 nsecs at the 50 MS/s for the CS8500).

For a CS8500 example, at a sampling rate of 50 MS/s on its one channel, a 3000 point acquisition would take about 60 ms. For a single-card system doing 333 Multiple Record scans of 3000 points each (offload time for the resulting 1 MS at 100 MB/s is about 10,000 ms), this gives a total cycle-time or minimum Pulse Repeat Interval (PRI) of:

[333 scans * (60 ms + 1 card * 0.040 ms) + 10000 ms + 30 ms rearm] = 30 msecs

Multiple Record mode provides acquisition coverage of 20 msecs out of every 30 msecs or 67%. Since this is better than the 50% coverage that is possible in Single Record mode, we recommended that the customer operate in Multiple Record mode.

Since they are scanning the inside surface of the pipe, we suggested a two-pass (or more) solution that would scan some on the first pass, and then cover the unscanned areas on the return-pass.

GaGe Case Recommended Products

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