Selecting between Resistance Temperature Detectors (RTDs) and Thermocouples is one of the most critical decisions for metrologists and industrial instrumentation engineers.
1. Accuracy and Repeatability Comparison
RTDs (especially PT100 and PT1000 sensors) offer exceptional linearity, repeatability, and ultra-high accuracy (±0.03°C for 1/10 DIN at 0°C). They are the preferred standard across the -200°C to +660°C temperature spectrum. In contrast, thermocouples offer much wider operating ranges (up to 1800°C for Type B, S, and R) but with significantly wider measurement tolerances (±1.5°C or ±0.4%).
2. 4-Wire True Kelvin Connection vs. 2-Wire / 3-Wire
For precision metrology and calibration reference standards, 4-wire Kelvin connection is mandatory. In a 4-wire configuration, two leads carry a constant excitation current while the other two leads measure the voltage drop across the platinum element with zero current flowing through the measurement circuit, completely neutralizing lead wire resistance errors.
3. Sensor Drift & In-Situ Verification
RTDs typically experience drift under 0.01°C per year when operated within specified limits, whereas thermocouples suffer from junction contamination and cold-working drift. Using a reference standard like the DB Metron PRT alongside the DB Therion or DB Thermobath guarantees audit-compliant calibration traceability.