Making Custom Oscilloscope Measurements
- 1. Making Custom Oscilloscope Measurements Using MATLAB and VB April 22nd, 2015
- 2. Signal Path Block Diagram - from Acquisition to Processing Amp Digitized Waveform A D C Analog-to-Digital Converter Display Processing Acquisition Memory Trigger Circuit SIMPLIFIED OSCILLOSCOPE BLOCK DIAGRAM Analog Waveform
- 3. Three Possible Communication Configurations Configuration 1: Remote Control Scope From Computer Computational results reside in MATLAB software Scope Platform GPIB / ENET Computer Platform Scope Software MATLAB
- 4. Three Possible Communication Configurations 4 Configuration 2: MATLAB Software Installed on Scope Scope Platform Scope Software MATLAB Computational results reside in MATLAB software
- 5. Three Possible Communication Configurations Configuration 3: MATLAB Software Integrated Within Scope Application MATLAB-assisted dynamic collaboration as the oscilloscope and MATLAB share native capabilities. Scope Platform DRIVER Scope Software MATLAB INLINE PROCESSING
- 6. Three Possible Communication Configurations Scope Platform Scope App Computer Platform Configuration 1: Remote Control Scope From Computer GPIB / ENET Scope Platform Scope AppMATLAB Configuration 2: MATLAB Installed on Scope Scope Platform Scope App Configuration 3: MATLAB Fully Integrated Within Scope Application Computational results reside in MATLAB software INLINE PROCESSING MATLAB-assisted DSO shares native capabilities Computational results reside in MATLAB software MATLAB MATLAB
- 7. Workflow Model for Incorporating A New Algorithm Appl Engr Prod Mngr Contacts applications Collects data, logs report, contacts product manager Engr Mngr Dsn Engr Evaluates request, prioritizes projects Assigns resources, places project in queue Already moved on to a different project, no longer needs measurement Six months later, implements inline measurement into firmware Releases firmware with feature included Notifies local rep Delivered to end user End User Traditional Model: Sales Engr Requires a new feature; contacts local representative with request Time Scale: 6 - 9 months Inline Processing Model: End User Incorporates new inline measurement today, and can begin to use it immediately Time Scale: Immediate Proprietary measurements can remain classified and do not need to be shared with scope vendor or the outside world
- 8. How Is A Measurement Selected? Traditional parameters added to the measurement
- 9. How Is A Custom Measurement Selected? Allows user-defined in-line custom measurements Custom parameters are added to the measurement list just like traditional parameters
- 10. Fully-Integrated Custom Measurement Add your own customized measurement or math function And the result is fully integrated into the scope process as a measurement or trace
- 11. Inline Custom Measurement Custom MATLAB parameter finds the time elapsed for half-life of the damped sine The value 3.149 is the number of cycles that have occurred when the signal reaches 50% of its peak amplitude
- 12. Real-Time Modification of Custom Measurement MATLAB dialog box displays MATLAB responses On-scope editor allows loading, saving, and real- time modification of script algorithms
- 13. Arbitrary Waveform Generated on Scope OutResult.Samples = InResult.Samples startData = 0 endData = OutResult.Samples newNumPoints = endData - startData ReDim newDataArray(OutResult.Samples) unscaledData = InResult.DataArray(False) Randomize Timer Pi = 3.14159 : TwoPi = 2.0 * Pi WaveLength = 0.02 ' as a fraction of the timebase WL = WaveLength * newNumPoints WN = TwoPi / WL TimeConstant = 0.1 ' as a fraction of the timebase TC = TimeConstant * newNumPoints A = 30000 Noise = 100.0 For i = WL To endData - 1 Y = A * (exp(-i/TC)) * sin(WN * i) Y = Y + Noise * (rnd+rnd+rnd+rnd+rnd+rnd-3.0) newDataArray(i) = Y Next OutResult.DataArray(False) = newDataArray The damped sinusoid was simulated mathematically (scope simulates but does not output waveform) Waveform now exists in scope memory buffer
- 14. Peak Decay Ratio Custom parameter finds the peak decay ratio of the damped sinusoid. The 0.82 reading indicates each peak in the waveform is 0.82 the amplitude of the adjacent previous peak.
- 15. Application Example: MATLAB Digital Filtering
- 16. MATLAB Butterworth Filter Swept Sine Low Pass Butterworth
- 17. MATLAB Butterworth Filter MATLAB Signal Processing Toolbox supports up to 500th order Butterworth filter This MATLAB filter was implemented with only 5 lines of code
- 18. Wavelet Transforms WformOut = WformIn1(1:2:end)-WformIn1(2:2:end); Because of vectorization in MATLAB, a Haar Wavelet can be performed using only one line of code: Applications for Wavelets include filtering, data compression, and signal processing
- 19. Notch Filter Swept Sine Notch Filtered Swept Sine
- 20. Example Mixing Mathematical Waveforms with Input (Real signal captured by the scope with noise added algorithmically) Pure Mathematical Gaussian Noise Input Signal Input Signal + Noise
- 21. Automatic Leveling Filter Filter removes slow mean variations by repositioning waveform data
- 22. User-designed FFT Windowing Input signal Custom window applied to data FFT is now performed on custom window Any FFT windowing algorithm can be used with FFT
- 32. Inverse FFT performed with one line of source code WformOut = ifft(WformIn1 + j*WformIn2);
- 33. Application Example: Graphic Programming with MATLAB
- 34. Processing Web Building parameters or math functions from basic building blocks
- 35. Processing Web Building parameters or math functions with MATLAB operators
- 36. Simulink Blocksets Can Be Used for Realtime Simulation
- 38. 3-D Display of Data Surface mesh shows progression of square wave over time
- 39. Rotating the Surface Viewing Angle Image vantage point can rotate on 3 axes while viewing this Swept Sine
- 40. Custom Display Techniques Waterfalls and 3-D Data Rotation
- 41. Custom Graphical User Interfaces Crest Factor is computed and displayed via a custom MATLAB graphical user interface
- 42. Application Examples: Custom Timing Measurements
- 44. EMC Risetime Custom Definition EMC Risetime Custom Definition IEEE Risetime Definition
- 45. EMC Risetime Custom Definition Custom EMC Pulse Measurement
- 46. Crossing Point Between Two Waveforms The editor is provided in the scope application In case of error, the status will be set to error and gives the number of the concerning line. Possible to write the code in a separate editor and import it Export the code to a file When saving the setup, the code will be saved internally for further processing, so no need to re-write it. Crossing point time between two waveforms Takes two internal parameters as input and gives one as an output The user provides the crossing level in the scope’s time@lvl parameter This combination uses the scope’s internal parameters as input
- 49. Waveform Correlation Customization allows the scope to apply the spreadsheet's correlation capability for waveform analysis
- 50. Waveform and measurement results can be "pushed" directly into a spreadsheet Measurements on spreadsheet- generated trace Trace generated from spreadsheet Acquired Trace
- 51. Application Example: Decision Process Math Operators
- 52. Dynamic Automation Controls Input Waveform Static Result Continuously Sampled Output Dynamic Automation Controls
- 53. MATLAB Dynamic Feedback During Testing h=actxserver('LeCroy.XStreamDSO'); vertoffset = get(h.Acquisition.C2.VerOffset,'Value') if (h.PassFail.Q1.Out.Result.Value) == 0 %% mask test fails vertoffset = get(h.Acquisition.C2.VerOffset,'Value') if (vertoffset > 0) %% trace offset is positive set(h.Acquisition.C2.VerOffset,'Value',(vertoffset + 0.005)); else set(h.Acquisition.C2.VerOffset,'Value',(vertoffset - 0.005)); end end 3 2 1 Custom scripts can use Automation Controls to act as a feedback mechanism to modify scope settings based on measurement results This example uses Automation Controls to automatically modify scope settings and move waveform clear of mask region = automation controls Mask test pass/fail result queried and scope channel vertical offset modified using Automation
- 54. Measurement on Trace 1 is Gated by Pulses of Trace 2 This example shows how a measurement definition can be dynamically determined by the properties of the waveform data itself. In this example, the portion of data where the measurement takes place on Trace 1 is dependent on the area marked between the two pulses of Trace 2.
- 55. Script has not begun computing average because Pass/Fail condition has not yet been True
- 56. Script begins averaging F8
- 57. Averaging continues on acquisitions only when Pass/Fail condition is True
- 58. Averaging pauses whenever Pass/Fail condition is False
- 59. Averaged waveform takes shape of C1 after 287 sweeps. 79 averages have taken place because Pass/Fail condition was True 79 out of 287 sweeps
- 60. Application Example: Linear Regression / Slope Intercept
- 61. Oxygen Depletion in a Muscle Fiber
- 62. Experiment to measure oxygen depletion in muscle fiber
- 63. Nitrogen is injected into container to displace oxygen
- 64. Trend line records oxygen level as a function of time
- 65. Long-term trend line can be extracted as a waveform
- 66. Long-term trend line of oxygen vs. time
- 67. Linear Regression to Determine Slope Intercept of Oxygen Depletion at t=0
- 68. Application Example: Precision Burst Timing
- 69. A ground-fault circuit interruptor (GCFI) is a device that disconnects a circuit whenever it detects that the electric current is not balanced between the energized conductor and the return, and is used to prevent injury caused by electric shocks. The measurement goal is to determine the exact amount of time that the 60 Hz cycle is present before the GFCI disables the output, and determine the start, stop, and duration of the ground fault circuit interrupter tripping time. Ground fault circuit interruptor GFCI Test Panel Ground Fault Circuit Interrupter Tripping Time Measurement
- 70. The exact start and stop time of each burst is variable. The burst length includes non-integer portions of the waveform cycles. Ground Fault Circuit Interrupter Tripping Time Measurement Challenge
- 71. Non-integer portions of the waveform are not measured by standard measurements (such as period) by oscilloscopes Timing measurement example using IEEE pulse parameters
- 72. GFCI Burst measurement requirement The use of cursors is not desirable because the burst length varies for each acquisition and the replacement of manual cursors by the operator significantly reduces overall test time Burst length varies from acquisition to acquisition and includes non-integer cyclical values. The exact size and shape of the non- integer portion is also variable. Example GFCI burst containing 6+ cyclesExample GFCI burst containing 5+ cycles
- 73. Zoom at start of burst showing fine placement of cursor on start time Zoom at end of burst showing fine placement of cursor on stop time The GFCI burst length varies for each acquisition. The manual placement of cursors and zooms (both of which need to be repositioned for every acquisition by the operator), is time-consuming and significantly reduces overall test throughput.
- 74. Scripting reports accurate burst start and stop time with 1 ns precision on 100 ms time capture window
- 75. Scripting dynamic repositions labels and dynamically zooms on every acquisition
- 76. Measurements-on-statistics shows range, median, mode, etc. of cumulative burst times
- 77. Script only 416 lines of code, covers all corner case scenarios, calculates burst times, and dynamically repositions zooms and labels
- 78. Application Example: RF Signal Processing
- 79. Hilbert Transform on 10 GHz RF Burst using In-line MATLAB
- 80. Hilbert Transform on 10 GHz RF Burst using In-line MATLAB
- 81. Hilbert Transform on Burst using In-line MATLAB
- 83. Sample MATLAB Routines can be downloaded from LeCroy’s Website Pre-written math and measurement samples on Teledyne LeCroy’s web site www.teledynelecroy.com/MATLAB
- 84. Application Note: Implementing MATLAB Filters on Waveform Data
- 85. Application Note: Decoding NRZ Data with MATLAB
- 86. Application Note: Interfacing with Simulink
- 87. Application Note: MATLAB COM object programming examples
- 88. Making Custom Oscilloscope Measurements Questions?