Case Studies
Non Destructive Testing (NDT) Scanning Inspection
The customer is testing interior of pipes with time-resolved fluorescence, a Photo Multiplier Tube (PMT), a transducer with 8MHz 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 3Kpts.
GAGE'S 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 50MS/s, a 3000 point (i.e. 3KS) acquisition would take about 60 m s (60 microseconds) to capture. To then transfer that 3KB acquisition to PC-RAM using PCI bus-mastering (at over 100MB/s), for display and saving, would take about 30 m s per channel. After that, a nominal 30 m s 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 m s + 1chan*30 m s + 1card*30 m s] = 120 m s
This gives a maximum repetitive-trigger Pulse Repeat Frequency (PRF) of up to 8333Hz [1/120 m s]. Assuming that the triggers arrive at this rate, the measurement coverage is about 50% since it takes 60 m s to capture the signal, and 60 m s for transfer and rearm.
Therefore, Single Record mode provides acquisition coverage of 60 m s out of every 120 m s, <50%. Remember this would be under DOS, and a tight MS Windows app might still be able to get you say, 5000-6000Hz PRF without missing triggers.
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 50MS/s for the CS8500).
For a CS8500 example, at a sampling rate of 50MS/s on its one channel, a 3000 point acquisition would take about 60 m s. For a single-card system doing 333 Multiple Record scans of 3000 points each (offload time for the resulting 1MS at 100MB/s is about 10,000 m s), this gives a total cycle-time or minimum Pulse Repeat Interval (PRI) of:
[333scans * (60 m s + 1card*0.040 m s) + 10000 m s + 30 m s rearm] = 30msecs
Multiple Record mode provides acquisition coverage of 20msecs out of every 30msecs 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.
PRODUCT RECOMMENDED
The customer purchased:
CS8500-2M;
External Clock Upgrade
Gage SDK pack on CD
This application note is provided "as is" without any warranties of any kind, either expressed or implied, including but not limited to the implied warranties of merchantability or fitness for a particular purpose. Gage Applied Technologies further does not warrant the accuracy and completeness of the material contained herein. Gage Applied Technologies may make changes to this material, or to the products described in it, at any time without notice.
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