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Scanimage 2018b introduces a new oscilloscope mode to visualize raw data acquired with a high speed digitizer (NI57xx). This data scope can be used to identify noise, digitizer saturation and signal bandwidth issues.

See Data Scope for an overview of the GUI.

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This feature is currently only available for use with FlexRIO digitizers (NI57xx). It is not available when X-series DAQ boards (63xx) are used to acquire PMTs.

 

 

Data Scope showing typical PMT power supply ripple noise at 320kHz in power spectrum.

Noise Sources

Different noise sources can be identified in different steps in the acquisition pipeline. To identifiy noise sources, start the datascope and set Pmt Power, Laser, and the Imaging status as described in the table below.

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The Data Scope automatically chooses an appropriate sampling frequency depending on the time scaling in the Time Plot. Use the mouse wheel to zoom into the time axis of the Time Plot.

To see low frequencies in the power spectrum, a longer time window needs to be chosen (i.e. use a time window >1s to see 50/60Hz noise).

Noise SourcePMT PowerLaserScanningNoise FrequencySymptomResolution
Power line noise / Ground loopOffShutteredOff50/60HzDrifting horizontal bars in imageConnect all equipment to same power outlet (Observe maximum allowed current on outlet).

Ambient Light

(e.g. Computer Monitor, Room Light)

OnShutteredOff100/120HzDrifting horizontal bars in imageShield microscope from ambient light.
PMT Power Ripple NoiseOnShutteredOff

100-500kHz

PMT gain dependent

Cross-hatch pattern in imageEnsure noise level is in low bits of signal.
Electrical Noise introduced by fast clock signalsOffShutteredOn> 1kHz  
Digitizer SaturationOnOnOnN/AScanImage shows overvoltage warningDecrease PMT gain and/or laser power.
Noise Pattern in Image

 

Typical noise pattern in image (frame rate: 30Hz). Horizontal bars: 60Hz power line noise. Cross-hatch pattern: PMT power supply ripple noise

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