Temperature measurement accuracy

Definition

Temperature accuracy refers to the maximum allowable deviation between the output of a temperature sensor (including transmitters or acquisition modules) and the actual temperature, reflecting measurement precision. It is determined by factors such as the sensor's tolerance class, transmitter accuracy, and cold junction compensation.

Temperature measurement accuracy is the maximum allowable deviation between a temperature sensor's output (including transmitter or acquisition module) and the true temperature. It reflects how precise the measurement is and is determined by factors such as the sensor's tolerance class, transmitter accuracy, cold junction compensation, and others.

Alias

Detailed explanation

Temperature measurement accuracy is typically expressed in two ways: 1. Absolute Error: e.g., ±0.5℃, indicating the maximum deviation at any measurement point does not exceed ±0.5℃. 2. Relative Error (per IEC 60584/IEC 60751): e.g., Type K thermocouple Class I tolerance = ±1.5℃ or ±0.4%·|t|, whichever is greater. Measurement accuracy ≠ resolution. Resolution is the smallest increment an instrument can display (e.g., 0.1℃), while accuracy is the deviation between the displayed value and the true value (e.g., ±1℃). High resolution does not guarantee high accuracy. The total accuracy of a complete temperature measurement chain results from the combination of multiple uncertainty sources: Total Measurement Error = √(Sensor Tolerance² + Transmitter Accuracy² + Cold Junction Compensation Error² + Lead Resistance Error² + Installation Error²) Key strategies to improve temperature measurement accuracy: - Select higher-grade sensors: Choose Class I (±1.5℃) over Class II (±2.5℃) for Type K thermocouples; choose Class A (±0.15℃) over Class B (±0.3℃) for PT100 sensors. - Shorten the signal chain: Place the transmitter close to the sensor to minimize interference from long leads. - Ensure accurate cold junction compensation: Use a constant-temperature cold junction block or ice point reference for high-precision applications. - Perform regular calibration: Traceability via dry-well calibrators, oil baths, or ice point references. - Install correctly: Ensure sufficient sensor insertion depth (≥ 10 times the probe diameter) to reduce conduction errors.

Calculation Formula

Typical Value

{"K-type thermocouple Class I": "±1.5°C or ±0.4%·t", "K-type thermocouple Class II": "±2.5°C or ±0.75%·t", "PT100 Class A": "±(0.15+0.002·|t|)°C", "PT100 Class B": "±(0.3+0.005·|t|)°C", "PT100 1/10 DIN": "±(0.03+0.0005·|t|)°C", "NTC thermistor": "±0.1~±1°C", "Infrared thermometer": "±1~±2% of reading"}

Unit

°C or %FS (Full Scale)