Data Scope Concepts¶
ScanImage® features an oscilloscope mode to visualize raw data acquired with a vDAQ or an NI FlexRio digitizer (NI57xx). This data scope can be used to identify noise, digitizer saturation and signal bandwidth issues.
See Data Scope Window for an overview of the GUI.
Note
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 identify noise sources, start the datascope and set Pmt Power, Laser, and the Imaging status as described in the table below.
Note
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).
NoiseSource |
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 outlet). |
AmbientLight(e.g.ComputerMonitor,RoomLight) |
On |
Shuttered |
Off |
10 0/120Hz |
Drifting horizontal bars in image |
Shield microscope from ambient light. |
On |
Shuttered |
Off |
100 -500kHz 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 |
||
DigitizerSaturation |
On |
On |
On |
N/A |
ScanImage® shows over voltage warning |
Decrease 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