How to use the Background Subtract mode in Spectradyne’s ViewerTM software
Estimating the electrical noise and using it to reduce background
…and here’s a transcript for your reading pleasure!
Hi I’m Ngoc Do, Application Scientist at Spectradyne! In this video we will take background subtraction and how the data is processed.
In the Currently Loaded window, I have a stats file from a standard measurement run. To get more detailed information, we have to go over to the Data Visualization tab. The “Peaks in the Raw Data” option allows for the display of peak information.
This plot shows the normalized signal in the y-axis in the acquired time interval, x-axis. Each dot represents a detected transit event, which is above the set baseline threshold. Blue dot is an event that has been excluded by the applied peak filters and red dot is an event that was not excluded.
Several parameters are recorded for each voltage spike and you can view these parameters by zooming in close to a particular event and selecting the dot. There are 4 parameters: associated diameter, transit time, signal-to-noise and symmetry. The diameter and S/N parameters are self-explanatory. Transit time is a measure of the length of time a detected event takes to move through the nanoconstriction. Symmetry refers to the peak symmetry.
Each parameter for all transit events can be plotted in a scatter graph against the diameter. Let’s take a look at a transit time versus diameter scatter plot. You can see the diameter is on y-axis and the transit time is on the x-axis. The blue population of dots represents excluded events based on peak filters applied. The red dot events are the bead population in our sample.
Now let’s go over background subtraction. Background subtraction is a way to visualize an estimation of the distribution of particle events that are caused by electrical noise. To access this mode, we can go to the “Subtract Backgrounds” box, select it, and then plot a parametric scatter graph.
You can see there are light and dark green dots in addition to the red and blue dots. The green dots are associated with false positive events with the dark green having been excluded by the applied peak filters and the light green having not been excluded.
This mode is a useful way to check that the peak filters applied are appropriate for the exclusion of all noise events and it can be a visual aid for defining custom peak filter when necessary.
This has been a deeper look into data analysis and background subtraction mode. I hope you find it useful. Further details are available in the instrument Operation Manual and if you have questions, contact us at email@example.com.
More training videos are also available on our website. Thank you for your attention!