Case Studies
High-Speed Digitization of Video Signals
THE PROBLEM
The customer is involved in a radar experiment requiring 12 bit digitization of two incoming video signals of approximately 250 KHz bandwidth.
In order to get good time resolution on these signals, it is desirable to sample them at rates of 2.5 MHz or higher. A sample rate of 5 MSPS would be ideal for the application, as it would over-sample by a factor of 20.
These signals must be sampled continuously for 10 seconds. No breaks are allowed during this time - in other words, no data must be missed.
During one day, there will be exactly 90 acquisition sequences, each lasting 10 seconds. Data from all of these acquisitions must be stored to an external SCSI drive bay.
The entire system must be rackmountable. The ideal packaging will be two chassis: one for the acquisition system and the other for the disk drive system with the two interconnected via a SCSI cable.
Finally, the system must be up and running within four to six weeks.
GAGE'S SOLUTION
The ideal solution will be based on the CompuScope 512/PCI, Gage's low-cost 12 bit PCI bus A/D card which is capable of simultaneously sampling at 5 MSPS on two input channels and streaming the digital data across the PCI bus without a break in the acquisition.
This board will be housed in the GagePC/PCI 586 - an industrial grade Pentium 200 MHz PC.
For a 10-second acquisition sequence, we will accumulate 50 Megasamples of data per channel at a sampling rate of 5 MSPS. This implies a total of 100 Megasamples for two-channel acquisition. Since each 12 bit sample occupies two bytes, the total memory requirement for each 10-second acquisition is 200 MB.
If, during a day, the customer performs 90 such acquisitions, they will need to store (90 * 200) MB or 18 Gigabytes of data in non-volatile memory such as a hard disk. In order to store the 18 GB of data, it will be necessary to have an external "Drive Bay" which will also be rackmountable. The two chassis will connect via a SCSI cable.
Since most of the high-speed PCI motherboards have a maximum of 128 MB DRAM which can be put on the CPU card, we suggest using an MMD 5400 PCI Memory board with 256 MB of memory. The CompuScope 512/PCI will stream data to the MMD board during the 10-second interval.
The software will set up the system to acquire 10 seconds of data by streaming it to the MMD 5400 card. Once the acquisition is finished, the data will be transferred to an external SCSI hard disk over the SCSI cable.
At the end of the day, the customer will be able to remove the hard disks from the system in order to transfer the data to another station.
Gage can put together such a system in approximately three weeks (mainly because of the delivery time on the disk drive system).
Finally, Gage highly recommends that the customer obtain a complete system from Gage, so that we may test the complete operation before shipping it.
PRODUCT RECOMMENDED
CompuScope 512/PCI-12 bit, 5 MSPS A/D card for PCI bus
GagePC/PCI 586-Industrial Grade Pentium 200 MHz PC
External rackmountable Drive Bay
MMD 5400 PCI Memory Board, with 256 MB of memory
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.
print this
email this
