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.
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.
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.
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 Source||PMT Power||Laser||Scanning||Noise Frequency||Symptom||Resolution|
|Power line noise / Ground loop||Off||Shuttered||Off||50/60Hz||Drifting horizontal bars in image||Connect all equipment to same power outlet (Observe maximum allowed current on outlet).|
(e.g. Computer Monitor, Room Light)
|On||Shuttered||Off||100/120Hz||Drifting horizontal bars in image||Shield microscope from ambient light.|
|PMT Power Ripple Noise||On||Shuttered||Off|
PMT gain dependent
|Cross-hatch pattern in image||Ensure noise level is in low bits of signal.|
|Electrical Noise introduced by fast clock signals||Off||Shuttered||On||> 1kHz|
|Digitizer Saturation||On||On||On||N/A||ScanImage shows overvoltage warning||Decrease PMT gain and/or laser power.|