Setting absolute scale with glassy carbon

This section teaches you how to set up absolute scale using glassy carbon (NIST SRM 3600) as a reference. It assumes you have completed Parts 1, 2 and 3. Note that you can use water (Part 4) or glassy carbon for absolute scale calibration in RAW. Glassy carbon is the more accurate approach, if available.

There are two ways to use glassy carbon as a standard in RAW. One way follows the NIST protocol, and will deliver the most accurate results. However, this method depends on all measurements having reliable flux measurements upstream and downstream of the sample. It also requires accurate measurements of the background of the glassy carbon measurement and the sample measurements. The second way is more similar to that used by water, in that it essentially ignores the background (assumes it to be small). This approach only requires regular normalization and a single measurement of the background for the glassy carbon sample.

A video version of this tutorial is available:

The written version of the tutorial follows.

Simple (ignoring background)

  1. Load/use the settings from part 3 (without absolute scale set from water, part 4). If you haven’t done those parts, the settings are saved available as settings.cfg in the calibration_data folder.

  2. Plot both of the glassy_carbon2_011_000x.tif.tif files, where x is 1-2, on the main plot.

  3. Average the glassy_carbon files you just loaded. Save the average in the calibration_data folder.

  4. Open the Options window by selecting “Advanced Options” in the Options menu.

  5. Click on the Absolute Scale section in the options list on the left.


  6. Click on the Glassy carbon “Set” button and select the A_glassy_carbon2_011__0001.dat file you just saved.

  7. Set the Sample thickness to 1.0 mm.


  8. Click “Calculate” button. You should get about 324.

    • Note: It is important that you not change your normalization settings once you have set the absolute scaling constant. If you do, you will have to recalculate the absolute scaling constant. Also, make sure absolute scale is turned off before you calculate the scale constant, otherwise you will get a bad scaling constant.
  9. Check the “Normalize processed data to absolute scale using glassy carbon” checkbox.

  10. Click “OK” to exit the advanced options panel, saving the changes.


  11. Save the settings for future use.