Signal DC offset only in MIM

Support & Troubleshooting Moku:Pro
1

Hi all,

I’m measuring a signal from a photodiode. If I use the oscilloscope or lock-in as a single instrument it shows up normally, positive signal with a zero DC offset, and it disappears when I block the detector. However, if I set up an oscilloscope or lock-in in multi-instrument mode (even if it’s the only instrument), there is an offset of ~30mV. If I block the signal or even disconnect the photodiode, the offset remains. I’m using 0 db attenuation and 50 ohm impedance for both configurations. I’m using DC coupling but even if I change it to AC coupling the offset still remains.

Is there any reason why an offset could appear only in multi-instrument mode? Any suggestions for troubleshooting this and acquiring more reliable data in MIM?

Thank you

2

Hi @sgmt,

Unfortunately I’m not able to reproduce what you’re describing, are you able to share with my what firmware version you are using? I have just been made aware that there was a bug in a previous firmware where there is this offset in Multi-Instrument Mode but not Single instruments, as you are describing. If this applies to you, I suggest upgrading to the latest firmware via the App or API, which you can find here.

Let me know if an update helps.

3

Hi @indira thank you for the response!
Indeed, I must have missed an update. After updating the firmware the problem seems to be solved!

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