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.

../_images/Data+Scope+PMT+Ripple.PNG

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.

PMTPowerRippleNoise

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

../_images/Noise.png

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