Open topic with navigation

AGC/RMS/Energy Absorption - Overview

The current scaling methods are based on a single value being calculated for an entire line. We then scale every sample in the line with this calculated value. ( i.e. We look for the Max Value in the line and calculate one scale factor from this. All samples are scaled to this value to ensure the line has the same amplitude ratios for both time and trace.) The following are the types of scaling methods:

• RMS Scaling - Calculates a single value for each trace, but may differ from trace to trace.

  RMS applies a scale factor to the entire trace, and because of this it will maintain a relative amplitude within the trace. This is not true on a trace to trace basis, as the window which is defined by a start and end time is used to compute an RMS scale factor for each individual trace.

• AGC Scaling - Computes a separate scale value for each sample of each trace.

  AGC applies a scalar to every sample of trace. This version uses a single window (AGC Window Length) starting at the top of the trace (eg. 500ms window at 2ms sample rate = samples 1-250). The AGC scalar then calculates an RMS value for all non-zero samples in the window.

  We then compute the scalar required to take this average value to the percent of Max Value for the data set. (eg. 16bit int average computed is 3000, 16% of 32767=5243, therefore the scalar is 1.74)  This scalar will be applied to the sample indicated at the application point, which has a default of 50%. (eg. 500ms window at 50% with a 2ms sample rate, applies to sample 125) Since this is the first window we apply the same scalar to the previous samples as well. (1-124).

  The window will then slide down 1 sample (2-251) and compute a scalar by the method mentioned above. It will then apply the scalar to sample 126 and continue to the end of the trace.

  This scale will corrupt the relative amplitude within a trace, and should only be used on data where users are not trying to locate amplitude anomalies.

Energy Absorption Ratio

- Uses a single window starting at the top of the trace, and applies the RMS ratio within the window above and below the sample, to every sample of the trace.