Maximum sampling rate of the myRIO-1900

[andreasbaldur]

Hi

I'm considering to use the myRIO-1900 to measure the return echo signal of a 200 kHz ultrasonic transducer. The reason is that I would like to do some real-time signal processing. My concern is that the available sampling rate is not sufficiently fast. The datasheet of the myRIO says that the "aggregate sample rate is 500 kS/s". Is there any ways that the sample rate can be increased when making proper use of the FPGA or is the 500 kS/s an absolute maximum?

Best Regards,

Andreas

[ikaiser]

Hi Andreas,

welcome to this forum!

Short answer: No.

Long answer:

• The sample rate is limited by the hardware Analog-to-Digital Converter (ADC), and it is 500k Samples per second, as you said.
• It is called "aggregated", as this specific device has only one ADC which reads all input channels one after another. In other words: The analog inputs are multiplexed towards the ADC. See page 7 of the device's manual for more information. With this, you can reads 500k S/s on one channel or e.g. 250k S/s on two channels each.
• The FPGA is connected to the AI pins through the ADC (see the block diagram on page 3 of the above-linked manual or in color here: NI myRIO-1900 Block Diagram (myRIO Module)). This makes sense, as the signal has to be converted somehow. So no matter what the speed of the FPGA is, the ADC is the limiting factor.

What is the maximum signal frequency that you want to measure? The 200 kHz itself or slight changes in the echoed signals (much higher than 200 kHz)? For just detecting the signal 500 kHz is enough, it's 2.5 times above it, so it obeys the WKS theorem / Nyquist theorem. For a good reproduction of the waveform you'd need something near 2 GHz anyways.