Oscilloscope Calibration and DC Gain Accuracy

One of the most important tests for an oscilloscope in Performance Verification or Calibration is DC Gain Accuracy. The DC gain accuracy is typically specified like this (example from the SDS3000X HD datasheet):

There are a number of ways to calculate the gain error on a range.

Most SIGLENT oscilloscopes utilize data collection across a number of points and then a line fit using the Excel formula: LINEST.

This can be a little different for some engineers doing calibration or PV, but this is referenced in our manuals. This article helps to explain how that is used.

The manuals suggest a number of test points and readings. Often 5 or 9 across the range.

Here is an example table of the settings, measurements, and error (the difference between):

In Excel, this table of data can be entered into the LINEST function like so:

DC Gain Accuracy Slope = LINEST(Verror1:Verror9, VSetting1:VSetting9)

You can learn more about this Excel function here:

https://support.microsoft.com/en-us/office/linest-function-84d7d0d9-6e50-4101-977a-fa7abf772b6d

This function returns an approximation for m and b in the linefit of y = m*x + b.

m or slope or gain in this instance is the first of 2 values returned.

By default, that is a decimal value. You can express it as a percentage and that is the gain error.

This result of 0.35% error is <1% error, so this range passes and is within the specification.

You can find the service manuals in with the other instrument documents for oscilloscopes here:

https://siglentna.com/resources/documents/digital-oscilloscopes/

Follow the test methodologies in the service guides to conduct performance verification on SIGLENT instruments.

For more information on service or calibration, check out: https://siglentna.com/service-and-support/calibration-certificate/

Or contact us directly at: [email protected]