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12 July 2017

The Periodic Table of Oscilloscope Tools: Measure

Measure tools are at the heart of an oscilloscope's utility
Figure 1: Measure
tools are at the heart
of an oscilloscope's
An oscilloscope is only as good as the tools it provides to users for acquiring, viewing, measuring, analyzing, and documenting waveforms. We present an overview of our deep collection of oscilloscope tools in our Periodic Table of Oscilloscope Tools, and in prior Test Happens posts, we've surveyed the Capture and View categories. Today we'll break down the Measure section of the Table.

As fundamental as the capture and viewing of waveforms is what oscilloscopes do, those functions are but a prelude to the real heart of an oscilloscope's utility: measurement of parameters and subsequent analysis.

The Third Step: Measure

With waveforms triggered on, acquired, and arranged on the display in the way that best illustrates their character, it's now time to begin applying your Teledyne LeCroy oscilloscope's battery of Measure tools. On the Periodic Table, we divide Measure tools into two subcategories: Parameters and Parameter Analysis (Figure 1).

First, let's take a look at the Parameters grouping:
  • All Instance parameters (most Teledyne LeCroy measurement parameters) are so-called because every occurrence of the measurement parameter is calculated and returned as a result. This permits simple and intuitive further analysis through a simple Statistics table, a Histicon/Histogram function display of the measurement parameter values, and Tracks/Trends of each value versus time and time-correlated to other acquired waveforms, or analysis of parameter values versus accumulated time. There is no limit on the number of instances that can be calculated.
  • Parameter Math lets users add, subtract, multiply, and divide two measurement parameters. Multiple operations can be cascaded to perform complex calculations. Rescaling of values may also be performed, with automatic calculation of correct units or manual override to user-defined units. Parameter math works with standard Teledyne LeCroy measurement parameters, user-defined Custom Measurements, or any combination.
  • Users can create Custom Measurements using MATLAB, MathCad, C++, VBScript, Jscript (JavaScript), or Excel. The Custom Measure capability in Teledyne LeCroy oscilloscopes provides for complete integration of the calculation within the oscilloscope program using ActiveDSO, which sends acquired data to the 3rd-party program and accepts a result back for native display within the oscilloscope. The data then is available for further processing, just like any other standard oscilloscope measurement. The Custom Measure result operates like any other built-in measurement parameter in that All Instance, Parameter Math, Statistics, Parameter Acceptance, Histicon/Histogram, and Tracks/Trends capabilities may be used on the Custom Measure result. Furthermore, Automation commands may be embedded within the Custom Math setup to further invoke other oscilloscope operations or to invoke a 3rd-party program.
With the Parameter Analysis tools, collections of measurements are massaged to yield further insights:
  • Measurement Statistics permit accumulation of billions of events as a measurement set with calculations for minimum, maximum, mean, standard deviation, and total number accumulated returned in a Statistics table. This adds tremendous flexibility to the oscilloscope for worst-case analysis or anomaly detection: The Statistics table can accumulate large numbers of values from one acquisition using All Instance capability, and then multiply the numbers of values accumulated through additional acquisitions.
  • Parameter Acceptance: Some Teledyne LeCroy software packages let you constrain measurement parameters to a vertically or horizontally limited range, or to occurrences gated by a second waveform. Furthermore, both constraints can operate together. Parameter Acceptance lets you exclude unwanted characteristics from your All Instance measurements. It is much more restrictive than Measure Gate, which is used only to narrow the span of analysis along the horizontal axis. Measurements so constrained may then be further analyzed with a Histogram, a Track, a Trend, or used in Parameter Math. Statistics will contain only the constrained measurement parameter set. Parameter Acceptance is also referred to as Qualified Parameters or Measure Accept.
  • Histograms graphically represent the distribution of a numerical measurement parameter set. They provide insight into complex signal behaviors (bimodal, multimodal, symmetric, skewed, normal, and so on) that cannot be understood in any other way. The power of Histograms is made possible with All Instance measurement capability, which permits fast and complete accumulation of up to 2 billion events in a Histogram from one or more acquisitions. Users may define the number of bins in the histogram and apply specialized histogram parameters to quantify the graphical behavior. Histicons are thumbnails that provide a convenient and summarized view of the measurement parameter distribution. Histicons are "histogram icons" and are an iconic display of a histogram distribution of a measurement parameter. Click on a histicon and it expands into a full-sized histogram.
Next time we'll turn our attention to the Math tools shown in the Periodic Table of Oscilloscope Tools.

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