Cantara/similarity-capacitor

Capacitor Similarity Calculator Skill

Guidance for working with CapacitorSimilarityCalculator in the lib-electronic-components library.

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For metadata-driven similarity architecture, see /similarity-metadata:

• SpecImportance levels (CRITICAL, HIGH, MEDIUM, LOW, OPTIONAL)
• ToleranceRule types (exactMatch, percentageTolerance, minimumRequired, etc.)
• SimilarityProfile contexts (DESIGN_PHASE, REPLACEMENT, COST_OPTIMIZATION, etc.)
• Calculator integration patterns and gotchas

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Overview

The CapacitorSimilarityCalculator compares capacitors based on:

• Capacitance value - Must match for high similarity
• Package size - 0402, 0603, 0805, etc.
• Voltage rating - Should be compatible
• Dielectric type - X5R, X7R, C0G, etc.

Applicable Types

ComponentType.CAPACITOR
ComponentType.CAPACITOR_CERAMIC_MURATA
ComponentType.CAPACITOR_CERAMIC_TDK
ComponentType.CAPACITOR_CERAMIC_SAMSUNG
ComponentType.CAPACITOR_CERAMIC_YAGEO
ComponentType.CAPACITOR_ELECTROLYTIC_NICHICON
// Any type starting with "CAPACITOR_"

Returns false for null type.

Similarity Scoring

| Condition | Score | |-----------|-------| | Same value, same package, same voltage | ~0.8+ | | Same value, different package | ~0.5-0.7 | | Same package, different value | ~0.3 | | Different everything | ~0.0-0.3 |

Capacitance Value Extraction

| MPN Pattern | Value | |-------------|-------| | 104 in MPN | 100nF (10×10⁴ pF) | | 103 in MPN | 10nF (10×10³ pF) | | 100N | 100nF | | 10U | 10µF |

Common Manufacturers & Patterns

Murata GRM Series

GRM 188 R 71 H 104 K A01 D
│   │   │  │  │ │   │ │   │
│   │   │  │  │ │   │ │   └── Packaging
│   │   │  │  │ │   │ └────── Termination
│   │   │  │  │ │   └──────── Tolerance (K=10%)
│   │   │  │  │ └──────────── Value (104=100nF)
│   │   │  │  └────────────── Voltage (H=50V)
│   │   │  └───────────────── Dielectric (71=X7R)
│   │   └──────────────────── Thickness
│   └──────────────────────── Size (188=0603)
└──────────────────────────── Series

Samsung CL Series

CL 10 B 104 K B8 NNNC
│  │  │ │   │ │  │
│  │  │ │   │ │  └── Packaging
│  │  │ │   │ └───── Voltage (B8=25V)
│  │  │ │   └─────── Tolerance (K=10%)
│  │  │ └─────────── Value (104=100nF)
│  │  └────────────── Dielectric (B=X7R)
│  └───────────────── Size (10=0603)
└──────────────────── Series

Yageo CC Series

CC 0603 KRX 7R 9 BB 104
│  │    │   │  │ │  │
│  │    │   │  │ │  └── Value (104=100nF)
│  │    │   │  │ └───── Voltage (BB=50V)
│  │    │   │  └─────── TCC code
│  │    │   └────────── Dielectric (7R=X7R)
│  │    └──────────────  Tolerance (K=10%)
│  └───────────────────  Size (0603)
└──────────────────────  Series

Cross-Manufacturer Matching

// Murata vs Samsung same value/size
calculator.calculateSimilarity("GRM188R71H104KA01D", "CL10B104KB8NNNC", registry);
// Returns >= 0.5 (both 100nF, 0603)

Dielectric Types

| Type | Characteristics | Temp Range | |------|-----------------|------------| | C0G/NP0 | Stable, low loss | -55 to +125°C | | X5R | Higher capacity | -55 to +85°C | | X7R | General purpose | -55 to +125°C | | Y5V | High capacity, variable | -30 to +85°C |

Test Examples

// Same Murata capacitor
calculator.calculateSimilarity("GRM188R71H104KA01D", "GRM188R71H104KA01D", registry);
// Returns ~0.8

// Same value, different package
calculator.calculateSimilarity("GRM188R71H104KA01D", "GRM21BR71H104KA01D", registry);
// Returns ~0.5-0.7

// Different values
calculator.calculateSimilarity("GRM188R71H104KA01D", "GRM188R71H103KA01D", registry);
// Returns ~0.3 (100nF vs 10nF)

// Cross-manufacturer
calculator.calculateSimilarity("GRM188R71H104KA01D", "CL10B104KB8NNNC", registry);
// Returns >= 0.5

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Learnings & Quirks

Value Notation

• E-series notation: 104 = 10×10⁴ pF = 100nF
• Last digit is multiplier (power of 10)
• 473 = 47×10³ pF = 47nF

Package Size Mapping

| Imperial | Metric | Murata Code | |----------|--------|-------------| | 0402 | 1005 | 155 | | 0603 | 1608 | 188 | | 0805 | 2012 | 21 | | 1206 | 3216 | 31 |

Voltage Code Variations

• Different manufacturers use different voltage codes
• Murata: H=50V, Samsung: B8=25V
• Always verify voltage compatibility

Dielectric Compatibility

• X7R and X5R are often interchangeable for general use
• C0G is preferred for precision applications

Unicode Gotcha: Micro Sign (Milestone 2, January 2026)

Critical Bug: The micro sign µ (U+00B5) becomes Greek capital MU Μ (U+039C) when uppercased:

"0.1µF".toUpperCase() // Returns "0.1ΜF" NOT "0.1µF"!

Impact: If parseCapacitanceValue() uses toUpperCase() before checking for "µF", the check fails silently, returning null. This causes capacitance comparison to be skipped, reducing similarity from ~1.0 to ~0.33 (package match only).

Solution: Replace µ→u and Μ→u before normalizing:

String normalized = value.replace("µ", "u").replace("Μ", "u");
normalized = normalizeValue(normalized); // Now safe to toUpperCase
if (normalized.contains("UF")) { // Matches both µF and plain UF

Lesson: Always handle Greek-origin SI prefixes (µ, Ω) carefully in string normalization logic.

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