Similarity Sensor

Sensor Similarity Calculator Skill

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

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

Overview

The SensorSimilarityCalculator compares sensors based on:

• Sensor family - Temperature, accelerometer, humidity, pressure, etc.
• Equivalent parts - Known interchangeable sensors
• Package variants - Same sensor in different packages

Applicable Types

ComponentType.SENSOR
ComponentType.TEMPERATURE_SENSOR
ComponentType.ACCELEROMETER
// Any type starting with "SENSOR_", "TEMPERATURE_SENSOR_", "ACCELEROMETER_"

Returns false for null type.

Similarity Thresholds

HIGH_SIMILARITY = 0.9;   // Same sensor, compatible packages
MEDIUM_SIMILARITY = 0.7; // Same sensor, incompatible packages
LOW_SIMILARITY = 0.3;    // Different sensor families

Sensor Families

Different sensor families always return LOW_SIMILARITY (0.3)

Temperature Sensor Equivalents

calculator.calculateSimilarity("DS18B20+", "DS18B20Z", registry);
// Returns 0.9 (same sensor, package variants)

Accelerometer Rules

Accelerometers are compared strictly by model:

// Same accelerometer
calculator.calculateSimilarity("ADXL345BCCZ", "ADXL345BCCZ-RL", registry);
// Returns 0.9 (same part, reel variant)

// Different models
calculator.calculateSimilarity("ADXL345", "ADXL346", registry);
// Returns 0.3 (different accelerometer)

Humidity Sensor Equivalents

Pressure Sensor Equivalents

Package Handling

Package compatibility is considered:

• TO-92, TO-226 - Through-hole, compatible
• SOT-23, TO-236 - SMD, compatible
• LCC, LGA, LFCSP, QFN, BCC - MEMS packages, compatible within group

Test Examples

// Same sensor
calculator.calculateSimilarity("DS18B20", "DS18B20", registry);
// Returns 0.9

// Temperature variants
calculator.calculateSimilarity("LM35D", "LM35C", registry);
// Returns >= 0.7

// Cross-family (different families)
calculator.calculateSimilarity("DS18B20", "ADXL345", registry);
// Returns 0.3

// Same accelerometer, reel variant
calculator.calculateSimilarity("ADXL345BCCZ", "ADXL345BCCZ-RL", registry);
// Returns 0.9

Metadata-Driven Implementation (January 2026)

Status: ✅ Converted (PR #120)

The SensorSimilarityCalculator now uses a metadata-driven approach with spec-based comparison.

Specs Compared

Implementation Pattern

// Short-circuit check for CRITICAL incompatibility
if (!sensorType1.isEmpty() && !sensorType2.isEmpty() && !sensorType1.equals(sensorType2)) {
    return LOW_SIMILARITY;
}

// Extract sensor type from MPN
private String extractSensorType(String mpn) {
    SensorFamily family = determineSensorFamily(mpn);
    return family.name(); // TEMPERATURE, ACCELEROMETER, etc.
}

// Extract sensor family with specific model number
private String extractSensorFamily(String mpn) {
    if (mpn.matches("^ADXL[0-9]+.*")) return "ADXL345", "ADXL362", etc.;
    if (mpn.matches("^DS18.*")) return "DS18B20", "DS18";
    // ... returns specific sensor model
}

// Equivalent sensor boost
if (areEquivalentSensorsByFamily(mpn1, mpn2, family1, family2)) {
    similarity = Math.max(similarity, HIGH_SIMILARITY);
}

Behavior Changes

Why more accurate: Metadata approach recognizes that ADXL345 vs ADXL346 share sensor type (ACCELEROMETER) and interface (SPI/I2C), giving them MEDIUM similarity instead of LOW. This is more accurate than treating them as completely different sensors.

Equivalent Sensor Groups

The calculator maintains equivalent sensor families:

• DS18B20 variants: DS18B20, DS18B20+, DS18B20Z all equivalent
• LM35 grades: LM35D, LM35C, LM35A all equivalent
• TMP36 variants: TMP36, TMP36GT9Z all equivalent
• MAX31820: Compatible with DS18B20
• SHT3x series: SHT30/31/35 within accuracy grades
• BMP/BME pressure: BMP280 ≈ BME280 for pressure

Learnings & Quirks

Temperature Sensors

• DS18B20: Digital, 1-Wire interface, ±0.5°C accuracy
• LM35: Analog output, 10mV/°C
• TMP36: Analog output, 10mV/°C, -40 to +125°C
• MAX31820: Drop-in replacement for DS18B20

Accelerometer Grades

• ADXL345B vs ADXL345: B is different interface option
• Different grades (BCCZ, BCCZ-RL) are same sensor

Humidity Sensor Accuracy

• SHT30: ±3% RH typical
• SHT31: ±2% RH typical
• SHT35: ±1.5% RH typical
• Higher number = better accuracy

Sensors Not Fully Supported

• HDC sensors may not be recognized by isSensor() method
• Some newer sensors may need pattern updates