Frequently Asked Questions

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General Questions Questions Related to Specific Gage Products Can't Find an Answer?

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General Questions

Q. I would like to sample two 40 MHz signals using a 200 MHz external clock, synchronized to a 10 MHz standard. What product can I use? My requirements are:

1. The sampling has to be taken at a very specific time and duration: 10 bursts of 8 Ksamples for 10 periods of time (each burst spaced by 1 ms and each period being 500 ms) using multiple recording.
2. I was planning to use external clock input only and feed it with the number of cycles required to take the samples. Everything has to be synchronized with a 10 MHz rubidium standard. Could the clock signal be used that way or does it have to be continually on?

Answer for Requirement 1:
You can use the CompuScope 2125 to solve this problem. You will also need to purchase the External Clock Upgrade for you to clock it externally. You must supply a trigger at the start of each new burst, if you want to use Multiple Recording.

If a 200 MHz external clock is used to sample two input signals simultaneously, then the sampling rate will be 100 MHz or 10 ns per sample.

Since each multiple record segment is 8K samples, 10 segments (or bursts) will mean that 80 Kilosamples of data will be stored in the on-board memory for each period.

The time for collecting all this data in the on-board memory is given by :

10 x 1 ms = 10 ms, as each trigger is 1 ms apart.

The data throughput for transfer from the on-board memory to the PC is approximately 2 MB/s on a Pentium computer.

The time required to transfer data to PC memory is given by the following expression :

Transfer Time = # Points / Throughput

As such, it will take (80 000 / 2 000 000) seconds, or 40 milliseconds to transfer the data.

In your application, the next set of bursts is going to repeat after 500 ms which is much longer than the 120 ms it will take you to acquire the data.

The above analysis suggests that your application will have enough time to acquire the data bursts without losing any data - guaranteed!

Answer for Requirement 2:
Yes, you can use "Burst Mode Clock", as you do not need the clock to be on continuously with the CompuScope 2125.

In this case, you do not need a Trigger signal for each burst; your clock will determine when you capture the signal.

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