Did you know Moku:Go's FRA automatically generates a swept sine wave?

Need to check the transfer function of your lowpass filter but not sure how to setup the Frequency Response Analyzer to do so? Check out the quick video and explanation below!

Moku:Go’s Frequency Response Analyzer (FRA) automatically generates a swept sine wave on both of it’s outputs when running the instrument. The amplitude of the swept sine is controlled in the Channel settings tab labeled ‘Amplitude’ and you can determine which output channel you are changing by looking at the setting box title which will say “In / Out (dB) 1” or “In / Out (dB) 2”.

The frequency range being swept over is the same as the FRA’s span which can be set in the Swept sine settings tab where you can manually enter the start and stop frequency of the sweep. You can also adjust the frequency sweep range by adjust the time base with your mouse/cursor by scrolling while hovering over the graph area.

Lastly, you can change Measurement modes to be “In / Out (dB)” or “Input (dBm)”. The In / Out measurement mode uses the swept sine you previously configured as the Out data and uses data from your Input to determine the transfer function. In this example, the RC filter network I have setup results in no change to the transfer function when adjusting the swept sine amplitude in the In / Out measurement mode, however, changing to the Input measurement mode shows changes in relative power as I adjust the swept sine amplitude. The short video below shows these measurement modes and more in action.

In this video I have my Moku:Go’s Input1 and Output1 connected to a simple RC filter network.

I hope this helps with your next FRA measurement, Go engineer!

Follow-up question regarding the FRA (actually on a Moku:Lab): is there a way to have a reference input? I.e., instead of measuring In1/Out1, have it measure In1/In2 (but still have the swept sine from Out1)?

You most certainly can! This can be done by enabling the Math channel at the bottom of the Channel settings drawer. Here you can change the operator and channel order. Here I have it set up to measure In1/In2. You can still export this trace data the same way you would with Channel 1 and Channel 2.