app

Charge-Storage Capacity

The CSC app compares charge obtained from time-domain current integration with charge obtained from cyclic-voltammetry integration for every readable CV/CT cycle in one or more Gamry DTA files.

Requirements And Launch

Each analyzed cycle must expose exact T, Vf, and Im columns and a positive scan rate.

labkit_CSC_app

Inputs And Selection

Add one or more CV/CT .DTA files. The selected file determines the current curve list, readout, and plots. Selecting another file resets the curve selection and default plot quantities to that file; it does not silently keep a cycle from the previous source. Saved projects preserve the successfully decoded file order through removal, later additions, and reopen.

The default curve selection is All cycles. Individual cycle selection updates the comparison readout for that cycle.

Basic Workflow

1. Add CV/CT files and select the active source.
2. Inspect all cycles for incomplete or anomalous edge cycles.
3. Choose Full, Cathodic, or Anodic comparison mode.
4. Enter electrode area when area-normalized CSC is required.
5. Optionally ignore the first and last cycle.
6. Configure the two plot panes and review CT/CV agreement.
7. Export all-cycle results and, when needed, column-oriented CV data.

Plot Behavior

All-cycle plots use a distinct color for each cycle; cathodic and anodic current branches use related dark/light variants. Time is shifted so each cycle begins at zero. Selecting new X/Y quantities refits the axes. Toggling trim overlays preserves the user's current view because it changes an overlay, not the underlying coordinate selection.

Ignore first/last cycle applies consistently to the all-cycle plot, result table, CSC export, and CV-data export. It is intended for known incomplete edge cycles and must not be used to hide arbitrary outliers.

Calculation Semantics

Time-domain charge integrates current against time. CV-domain charge integrates current against potential and divides by positive scan rate. Each line segment is split at a current zero crossing so cathodic and anodic contributions are assigned without smearing a sign change across one trapezoid.

Q_CT,cath = integral |I(t)| dt over cathodic current
Q_CT,anod = integral I(t) dt over anodic current
Q_CV      = integral I(V) dV / scanRate, split by current sign
CSC       = 1000 * Q_C / area_cm2

Full mode sums positive cathodic and anodic charge magnitudes. Relative difference is 100 * abs(Q_CT - Q_CV) / max(abs(Q_CT), abs(Q_CV)), with zero reported when both charges are zero. dtErr reports the maximum discrepancy between measured time increments and abs(dV)/scanRate over valid segments.

Without a valid positive area, charge comparison remains available but CSC fields in mC/cm^2 are NaN.

Outputs

Export all cycles CSV writes one row per included file cycle with source, cycle, mode, scan rate, area, CT and CV cathodic/anodic/full charges, selected charge and CSC values, absolute/relative difference, time-step consistency, and status fields.

Export CV data CSV writes potential plus paired current and scan-rate columns for replotting and independent calculation. When all exported cycles share the same potential vector, they occupy one file. When vectors differ, the app writes one CSV per source item using the selected filename as a stem. Each export action has its own .labkit.json provenance manifest.

Use Without The GUI

[item, status] = labkit.dta.loadFile("cv.DTA", "cvct");
assert(status.ok, status.message);
curve = item.curves(1);

options = struct("scanRate", 0.05, ...
    "area_cm2", 0.05, "mode", "Full");
result = csc.analysisRun.computeCSC(curve, options);
assert(result.ok, result.message);

Function Reference

The generated pages for computeCSC and chargeDensity state the exact numeric inputs, units, sign conventions, outputs, invalid-area behavior, executable examples, and related APIs used outside the GUI.

Errors And Limitations

• Scan rate must be finite and positive.
• Required column names are exact; a visually similar arbitrary table is not accepted as a CV/CT cycle.
• Area normalization is omitted rather than guessed when area is invalid.
• Agreement between CT and CV integration is a consistency measurement, not proof that the electrochemical experiment is otherwise valid.

Related Topics

• Electrochemistry family
• DTA Library
• API Reference