IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 55, NO. 2, APRIL2006 493 Software Customization to Provide Digital Oscilloscope With Enhanced Period-Measurement Features Maria Grazia D’Elia, Consolatina Liguori, Member, IEEE, Vincenzo Paciello, and Antonio Pietrosanto, Member, IEEE Abstract—This paper tackles the problem of signal period mea- surements by means of oscilloscopes. First, the performance of two last-generation scopes, implementing a zero-crossing algorithm, is evaluated. Then, after a brief resume of alternative measure- ment techniques, a solution to enhance the period-measurement capability of scopes is proposed and implemented in the LeCroy WaveMaster 8620A software. Finally, the results of the tests car- ried out on different signal waveforms are reported and analyzed. Index Terms—Digital instrument, digital signal processing, level-crossing problems, period measurement, uncertainty evaluation. I. I NTRODUCTION T HE NEWEST developments in analog front end and trig- ger circuit bandwidth (up to 10 GHz), as well as in analog- to-digital converter (ADC) sampling rate (20 Gsample/s), have produced, together with long dynamic random access memory (DRAM) data rates (up to 20 GB/s), significant advances in the realization of high-performance hardware platforms for digital oscilloscopes [1]–[4]. Moreover, on-board digital signal processing has made oscilloscopes evolve into the most valu- able tool utilized in the development of all forms of electronic equipment. Digital signal processing has been getting increasingly wide- spread during the last decade, thanks to the availability of ad hoc processors [the so-called digital signal processors (DSP)], which offer high computational power at acceptable cost. Electronic instruments, including DSP, can see both their performance and their features rise significantly. Oscilloscopes, in particular, can use the power of digital signal processing both to implement amplitude and frequency- domain measurement options and to increment acquired- sample resolution by suitable algorithms. In order to successfully reach these goals, granting that the quality of measurements be comparable with the cost of very high-performance instruments, the implemented algorithms should be both robust versus measurement parameters, and fast in run time. Their sensitivity to either user-defined or incon- Manuscript received June 15, 2004; revised December 20, 2005. The authors are with the Department of Information Engineering and Electric Engineering, University of Salerno, 84084 Fisciano, Italy (e-mail: mgdelia@unisa.it; tliguori@unisa.it; vpaciello@unisa.it; apietrosanto@ unisa.it). Digital Object Identifier 10.1109/TIM.2006.870128 trollable parameters, like sampling frequency, record length, signal waveform, and noise level, should be minimum. At the same time, the computational burden should be so low that the response time still be acceptable also in case of acquisitions characterized by fast time base and high record length. It is really difficult to believe that the tradeoff between these opposite needs can be achieved by manufacturers for all measurement functions (rms, peak, period, frequency, rise time, etc.) provided by oscilloscopes. The manufacturer’s choice usu- ally falls on algorithms mainly characterized by low computa- tional burden that assures proper working in the most common conditions, thus, accepting that they may be inadequate in some boundary cases. The problem is that oscilloscope manufacturers rarely give information about this boundary as well as they do for measurement accuracy. The consequence is that users who want to know the actual limits and performance of the oscil- loscope measurement algorithms must do them by themselves. The method of exhaustive verification is often hard to be run, since the numerous measurement parameters to be explored would require a very high number of tests. This means that users must trust their measurement expertise to detect, during the daily use of the instrument, rough errors due to limited performance of some signal processing algorithms. On the other hand, thanks to the choice of all major oscillo- scope manufacturers of substituting on-board installed propri- etary operating systems [1]–[4] with the widespread Microsoft Windows, measurement software features today could be in- creased by the user. Some of the last generation of oscilloscopes, in fact, allow creating custom parameter measurements or math functions in the scope’s user interface. Unique or proprietary MATLAB, Mathcad, VBScript, or even Excel calculations can be selected like any other installed parameter or math function, and the results displayed on the scope screen. These features can be used to add new measurement functions that can be recalled by the user in those cases where evident limits of the default measurement functions have been highlighted. In this framework, the authors have tested the top-level products of Tektronix and LeCroy in the period measurement of typical signals, exploring parameters like: noise level, number of periods, and number of samples acquired in the period. Both scopes adopt a simple zero-crossing method, which is not applicable to all waveforms. In this paper, the test results are widely discussed. 0018-9456/$20.00 © 2006 IEEE