One of the most useful features of LeCroy Oscilloscopes is the ability to process multiple measurements as waveforms that can be subsequently studied using all the built-in analysis tools available in the scope. The three parameterbased waveform tools are called Trend, Track, and Histogram.
Figure 1 is a conceptual diagram showing the flow of data within the oscilloscope.
The Trend Function is a waveform composed of parameter measurements arranged in the order the measurements were made. There is one value for each measurement and the function plots the measured values vs. the order number. Trends can contain up to 1 million values.
The Track function, like the Trend is composed of measured parameter values in the order they were taken. But the data is resampled so that the Track waveform is time coherent with the source trace. So if, for example, you measured pulse period, the Track function would show a single period value for the duration of each cycle in the source waveform. This means that the Track function plots parameter value versus time. Due to the time synchronization, the Track function contains many redundant values, and the number of points in the Track function is identical to the number of samples in the source waveform.
The Histogram function plots the number of parameter measurements within a small range, known as a bin, as a function of the parameter value. The histogram can use from 20 to 2000 bins and it can hold up to 2 billion measured values. The histogram shows the probability density of the parameter values.
Figure 2 shows an example of each of these functions. The upper trace, C2, is the acquired waveform, which is a phase modulated 500 MHz sine wave. Trace F1 is the track of parameter P1, the time interval error (TIE) of the acquired waveform. The TIE parameter essentially measures the instantaneous phase of the modulated carrier. The track of TIE shows the cycle-bycycle variation in phase, which is the modulating waveform.
Trace F2 is a histogram of the TIE parameter. It shows the number of values within an incremental range (bin) of the TIE parameter value. In this example the histogram contains over 7.2 million measurements as indicated in the trace annotation box for F2. Parameters P4, P5, and P6 are a few of the 19 histogram specific parameters that read the mean, standard deviation, and range of the histogram directly.
Trace F3 is a trend of parameter P2, which is measuring the topeak value of the acquired waveform, C2. The peak-to-peak parameter produces one value per acquisition. In this example we see a history of 100 peak-to-peak measurements. The horizontal axis is the measurement number. The oldest data is on the left side of the screen and the newest data is to the right.
The Track, Trend, and Histogram traces can be invoked from the parameter setup dialog box, as shown in Figure 3. The traces themselves are math traces and can also be accessed directly through the math setup dialog box.
Each of these measurement analysis tools is extremely useful. The Trend function is usually applied as a data logger showing the history of measured parameter values. If trends of two or more parameters are created simultaneously, these can be plotted on an X-Y display to see functional relationships. Examples of this application are shown in LAB731.
The Track function is used in applications that require time synchronization. The example in Figure 2 showed the Track function being used to demodulate a phase modulated signal and extract the modulation waveform as shown in LAB’s WM_405A, and WM_407A. It can also be used to locate anomalous parameter values in a long acquisition. All you have to do is align the Track function with a zoom of the source waveform and use multizoom to expand them both simultaneously. Examples of this application are shown in LABs 727A, 730A, and WM_729. Histograms are used for statistical analysis of measured parameter values. Examples of more specific uses are found in LAB’s 718 -721.
LeCroy uniquely allows users to track, trend, or histogram any of our over 158 available parameters. Additionally these functions, being waveforms, can be further analyzed using any of LeCroy’s powerful math tools such as averaging, fast Fourier transform (FFT), or digital filtering.