similarity-sensor

name	similarity-sensor
description	Use when working with sensor similarity calculations - comparing temperature/accelerometer/humidity sensor MPNs, understanding sensor families, equivalent parts, or sensor-specific similarity logic.

Sensor Similarity Calculator Skill

Guidance for working with SensorSimilarityCalculator 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 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

Family	Detection Patterns
Temperature	LM35*, DS18*, TMP*, MAX318*
Accelerometer	ADXL*, MMA*, LIS2*, LIS3*, BMI*, ICM*
Gyroscope	L3GD*, ITG*, MPU*
Humidity	SHT*, HIH*, AM*, HDC*
Pressure	BMP*, BME*, MS56*, LPS*
Combined	BME* (temp+humidity+pressure), MPU* (accel+gyro)

Different sensor families always return LOW_SIMILARITY (0.3)

Temperature Sensor Equivalents

Sensor	Equivalents
DS18B20	DS18B20+, DS18B20Z, DS18B20/T
DS18B20	MAX31820 (compatible)
LM35	LM35D, LM35C, LM35A (grade variants)
TMP36	TMP36GT9Z, TMP36FS

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

Family	Compatible Parts
SHT3x	SHT30, SHT31, SHT35 (within accuracy grades)
HIH613x	HIH6130, HIH6131
HDCx080	HDC1080, HDC2080

Pressure Sensor Equivalents

Family	Compatible Parts
BMx280	BMP280, BME280 (pressure compatible)
MS56xx	MS5611, MS5607

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

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Metadata-Driven Implementation (January 2026)

Status: ✅ Converted (PR #120)

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

Specs Compared

Spec	Importance	Tolerance Rule	Description
sensorType	CRITICAL	exactMatch	TEMPERATURE, ACCELEROMETER, GYROSCOPE, HUMIDITY, PRESSURE, COMBINED
family	HIGH	exactMatch	LM35, DS18, ADXL, MMA, SHT, BME, BMP, etc.
interface	MEDIUM	exactMatch	I2C, SPI, 1-Wire, Analog
package	LOW	exactMatch	TO-92, SOIC, LGA, QFN, BCC, etc.

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

Comparison	Legacy Result	Metadata Result	Notes
DS18B20 vs DS18B20	0.9	1.0	Identical sensor
DS18B20+ vs DS18B20Z	0.9	1.0	Equivalent variants boost
ADXL345 vs ADXL345	0.9	1.0	Identical
ADXL345 vs ADXL346	0.3	0.703	Same type + interface = MEDIUM
ADXL345BCCZ vs ADXL345BCCZ-RL	0.9	0.976	Same sensor, packaging variant
LM35 vs ADXL345	0.3	0.3	Short-circuit on sensor type

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

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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