We have a LabVIEW program driving a Red Pitaya, generating waveforms over a frequency range, then acquiring results from a circuit. Some recent testing shows an odd behavior around 235kHz, where there is a small increase in the generated signal amplitude leading up to this frequency, then it tapers back down to normal:
Frequency (kHz) and Amplitude (Vpp) [generating 2.0Vpp sine wave]
100 2.072
150 2.073
200 2.084
225 2.112
235 2.116
240 2.115
250 2.107
275 2.090
300 2.080
350 2.072
400 2.070
We have measured this generated signal with a "real" oscilloscope, too. Same behavior.
Example: Signal cable running from output channel 1 to input channel 1 (with 50 ohm termination).
This can be duplicated using Red Pitaya's "Generator & Oscilloscope" application.
1) Use "Signal generator" tab to create signal on appropriate channel
2) Use "Measure" tab to view Amp: Vpp
Sweep through the frequency range and observe.
We have two RP's and they both have this behavior, on both channels.
Does anyone else also observe this behavior, and does anyone have any clues?
generate with odd behavior
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Re: generate with odd behavior
2.116/2.0 => +5.8%
20*log(2.116/2.0) = +0.49db
That's not bad.
All devices have a frequency response. I know that the input (scope) has frequency response correction factors. I do not know if the DAC, sig gen, does.
The spec says: Gain error: <5%(G) and foot note (G) says: further corrections can be applied to make it better.
20*log(2.116/2.0) = +0.49db
That's not bad.
All devices have a frequency response. I know that the input (scope) has frequency response correction factors. I do not know if the DAC, sig gen, does.
The spec says: Gain error: <5%(G) and foot note (G) says: further corrections can be applied to make it better.
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