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Analysis Tools

How to measure, analyze, and export simulation results in GeckoCIRCUITS.

Duration: 15 minutes

Prerequisites: Running Simulations

The SCOPE (Oscilloscope)

The SCOPE block is the primary tool for viewing simulation results.

Opening the Scope

Double-click any SCOPE block in the schematic to open the waveform viewer.

Scope Channels

Each SCOPE input terminal corresponds to a channel. Channels display:

  • Voltage signals from voltage probes
  • Current signals from current probes
  • Control signals from control blocks
Action How
Zoom in Scroll wheel up
Zoom out Scroll wheel down
Pan Click + drag
Auto-scale Right-click > Auto Scale
Reset view Right-click > Reset

Measurement Tools

Cursors

Use cursors for precise measurements:

  1. Right-click in the scope > Add Cursor
  2. Drag cursor to the point of interest
  3. Read the time and value display

Using Two Cursors

With two cursors, you can measure:

  • Time difference (delta t) between two points
  • Value difference (delta V or delta I)
  • Frequency = 1 / delta t

Average and RMS

For periodic signals, the scope can compute:

Measurement Formula Use For
Average (1/T) x integral of v(t) dt DC component
RMS sqrt((1/T) x integral of v^2 dt) Power calculations
Peak max(v(t)) Component stress
Peak-to-peak max - min Ripple measurement

Key Measurements in Power Electronics

Ripple

Voltage or current ripple is the AC component on top of the DC:

\[\Delta V = V_{max} - V_{min}\]
\[\text{Ripple (\%)} = \frac{\Delta V}{V_{avg}} \times 100\]

Efficiency

\[\eta = \frac{P_{out}}{P_{in}} = \frac{V_{out} \times I_{out}}{V_{in} \times I_{in}}\]

Measure input and output power using voltage and current probes.

Power Factor

For AC circuits:

\[PF = \frac{P_{real}}{P_{apparent}} = \frac{P}{V_{rms} \times I_{rms}}\]

THD (Total Harmonic Distortion)

\[THD = \frac{\sqrt{V_2^2 + V_3^2 + V_4^2 + ...}}{V_1}\]

Use the FFT view in the scope for harmonic analysis.

FFT Analysis

The scope includes a frequency-domain view using Fast Fourier Transform:

Viewing the Spectrum

  1. Run simulation to steady state
  2. Open scope
  3. Switch to FFT view (if available)
  4. Observe harmonic content

What to Look For

Feature Indicates
Fundamental peak Switching frequency
Harmonics Integer multiples of f_sw
Low-frequency content Control loop dynamics
Broadband noise EMI concerns

Exporting Data

Export to CSV

From the scope:

  1. Right-click > Export Data
  2. Choose CSV format
  3. Select channels to export
  4. Save file

CSV Format

Time,Channel1,Channel2,Channel3
0.000000,0.0,0.0,0.0
0.000001,12.1,0.5,48.0
0.000002,12.2,0.6,0.0

Post-Processing

Exported data can be analyzed in:

  • MATLAB/Octave - data = readmatrix('output.csv');
  • Python - data = numpy.loadtxt('output.csv', delimiter=',')
  • Excel - Open directly as CSV

Thermal Measurements

When thermal simulation is enabled:

Measurement Unit Description
Junction temperature C Semiconductor die temperature
Switching losses W Energy lost during transitions
Conduction losses W I^2 x R losses during ON state
Total losses W Switching + conduction

See Thermal Simulation Tutorials for details.

Tips for Good Analysis

  1. Wait for steady state - Don't measure during startup transients
  2. Use enough cycles - Average over multiple switching periods
  3. Check time step - Too large a step hides high-frequency content
  4. Compare with theory - Verify results match analytical predictions
  5. Document settings - Record simulation parameters with results

Next Steps