Accredited Resistance Thermometer Calibration Services
In precision thermal processing, the Resistance Temperature Detector (RTD) is the industry standard for stability and accuracy. At DRS Technologies, we provide expert resistance thermometer calibration services to ensure your sensors—whether Pt100, Pt1000, or copper-based—maintain their critical $R$ vs. $T$ relationship. Our laboratory utilizes high-precision resistance bridges and stabilized thermal baths to verify your sensors with millidegree resolution.
Why Resistance Characterization is Essential
Resistance thermometers operate on the principle that the electrical resistance of a metal increases as temperature rises. However, physical stress, moisture ingress, and “sensor poisoning” can cause the platinum element to shift, leading to significant measurement drift. Regular calibration by DRS Technologies ensures that your sensors adhere to the ITS-90 (International Temperature Scale of 1990) and meet the alpha coefficient requirements (typically $0.00385 \Omega/\Omega/^\circ\text{C}$) used by your controllers.
Our Technical RTD Calibration Process
Our metrology specialists employ a comprehensive verification protocol using comparison and fixed-point techniques:
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Insulation Resistance (IR) Audit: We test the resistance between the sensor leads and the outer sheath. A drop in IR (often caused by moisture) can create “shunt” paths that lead to falsely low temperature readings.
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Hysteresis and Self-Heating Analysis: We verify that the sensor returns to its baseline resistance after thermal cycling and monitor the “self-heating” effect caused by the excitation current from the transmitter.
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Comparison Calibration: Sensors are placed in highly uniform stirred liquid baths alongside a Standard Platinum Resistance Thermometer (SPRT) reference. We test at multiple points across your operating range (e.g., $-196^\circ\text{C}$ to $660^\circ\text{C}$).
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Callendar-Van Dusen Coefficient Calculation: For high-precision applications, we can calculate the specific constants ($A, B, C$) for your individual sensor, allowing your transmitter to map resistance to temperature with maximum accuracy.
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Certification and NIST Traceability: Every unit is returned with a calibration certificate featuring As-Found/As-Left data, resistance values at specific temperatures, and documented NIST traceability.
Specialized Support for Resistance Measurement
DRS Technologies supports a wide array of resistance-based temperature technology:
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Pt100 and Pt1000 Sensors: Calibration for both thin-film and wire-wound elements.
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Secondary Standard PRTs: High-precision calibration for laboratory reference thermometers.
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Smart Transmitters: Verifying the 4-20mA or digital output relative to the RTD input.
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Sanitary/Hygienic RTDs: Calibration for sensors used in food, beverage, and pharma CIP processes.
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Multi-Point RTD Assemblies: Verifying profile accuracy for large tanks or reactors.
Frequently Asked Questions
What is the difference between a 2-wire, 3-wire, and 4-wire RTD?
The number of wires determines how the system compensates for lead-wire resistance. 4-wire RTDs are the most accurate as they completely eliminate lead-wire error. During calibration, DRS Technologies verifies that your leads are not introducing parasitic resistance that could bias your results.
How often should an RTD be calibrated?
Standard industrial RTDs should be calibrated every twelve months. However, sensors subjected to extreme vibration or high-temperature cycling should be checked every six months, as mechanical stress can fracture the fragile platinum wire.
What is “Alpha” ($0.00385$)?
Alpha represents the temperature coefficient of resistance. It is the average change in resistance per degree Celsius between $0^\circ\text{C}$ and $100^\circ\text{C}$. Most industrial sensors use the “DIN” standard of $0.00385$. We verify this coefficient during calibration to ensure compatibility with your instrumentation.