A Complete NIST-Traceable Calibration Capability
Every temperature sensor leaving the Thermometrics Corporation Northridge facility is calibrated against working standards whose traceability terminates at the National Institute of Standards and Technology (NIST). Our in-house calibration laboratory operates under an ISO 9001:2015 and AS9100D quality management system, with formal procedures controlling environment, reference standards, technique, and the propagation of uncertainty.
We calibrate platinum RTDs (PT100 and PT1000) and base-metal, noble-metal, and refractory thermocouples of every standard type from a cryogenic floor at the boiling point of liquid nitrogen (-196 °C) to a high-temperature ceiling of +1700 °C. Calibration is performed using both fixed-point realization of the International Temperature Scale of 1990 (ITS-90) and comparison against Standard Platinum Resistance Thermometers (SPRTs) and reference noble-metal thermocouples.
Every sensor returned to a customer is accompanied by a numbered certificate of calibration that documents reference standards, methodology, environmental conditions, the full uncertainty budget, and — for re-calibration jobs — both as-found and as-left data so engineers can quantify drift between intervals.
- NIST-traceable working standards across the full temperature range
- Fixed-point and comparison calibrations per ITS-90
- RTDs (PT100, PT1000) and thermocouples (B, E, J, K, N, R, S, T)
- Certificate of calibration with full uncertainty budget
- As-found / as-left data on every re-calibration
- Standard 5–7 business day turnaround; rush and same-day available
Why Calibration Matters
The metrological value of a temperature measurement is not the indicated reading — it is the indicated reading plus its documented uncertainty. Without a traceable calibration certificate, a sensor cannot be used as evidence in a regulated environment, cannot be cited in a research paper, and cannot anchor a process-control system that must hold a critical tolerance.
Quick Capability Summary
Range: -196 °C to +1700 °C
Methods: Fixed-point, comparison
Scale: ITS-90
Sensors: RTDs, thermocouples
Traceability: NIST
Turnaround: 5–7 days standard, 2–3 days rush
Calibration Methods per ITS-90
Thermometrics performs calibrations using the two methods defined for industrial and laboratory metrology under the International Temperature Scale of 1990: fixed-point realization for the highest accuracy at metrologically defined temperatures, and comparison calibration against transfer-standard reference thermometers for arbitrary user-specified setpoints.
Fixed-Point Calibration
The unit under test is immersed in a metal-freeze or triple-point cell that realizes a defined phase-transition temperature of the ITS-90 (for example, the triple point of water at 0.01 °C, the freezing point of zinc at 419.527 °C, or the freezing point of silver at 961.78 °C). Because the plateau temperature is fixed by physics rather than by a reference instrument, this method yields the lowest achievable uncertainty.
Comparison Calibration
The unit under test is placed alongside one or more NIST-traceable transfer-standard thermometers in a stirred-fluid bath, dry-block calibrator, or tube furnace. Readings are taken simultaneously at customer-specified setpoints across the sensor's working range, and the unit's deviation from the reference is recorded. This is the standard method for routine industrial calibrations and is used for any setpoint that is not a defined fixed point.
SPRT Reference Standards
Our primary reference instruments for the comparison range -200 °C to +961 °C are 25.5 Ω capsule and long-stem Standard Platinum Resistance Thermometers calibrated at NIST or at an accredited NVLAP / A2LA secondary laboratory. SPRTs are characterized at multiple fixed points and used with high-precision AC or DC resistance bridges.
Reference Thermocouples
For temperatures above the silver point and into the refractory range (up to +1700 °C), Thermometrics uses Type S, Type R, and Type B noble-metal reference thermocouples calibrated against fixed-point cells and high-stability tube furnaces. Reference noble-metal thermocouples are re-characterized on a defined interval per our quality manual.
Sensor Types We Calibrate
Thermometrics calibrates new manufacture, customer-supplied assemblies, and field-returned sensors of any manufacturer. Both platinum RTDs and all eight letter-designated thermocouple types are supported across our published temperature range.
| Sensor Family | Designation | Typical Range | Common Tolerance | Notes |
|---|---|---|---|---|
| RTD — Platinum | PT100 | -200 to +850 °C | Class A, Class B, 1/3 DIN | 100.00 Ω at 0 °C; IEC 60751 |
| RTD — Platinum | PT1000 | -200 to +500 °C | Class A, Class B, 1/3 DIN | 1000.00 Ω at 0 °C; IEC 60751 |
| Thermocouple — Base | Type J (Fe / Cu-Ni) | -210 to +1200 °C | Special: ±1.1 °C or 0.4% | Iron / constantan; reducing atmospheres |
| Thermocouple — Base | Type K (Ni-Cr / Ni-Al) | -270 to +1372 °C | Special: ±1.1 °C or 0.4% | General-purpose, oxidizing/inert |
| Thermocouple — Base | Type T (Cu / Cu-Ni) | -270 to +400 °C | Special: ±0.5 °C or 0.4% | Cryogenic; food and moist environments |
| Thermocouple — Base | Type E (Ni-Cr / Cu-Ni) | -270 to +1000 °C | Special: ±1.0 °C or 0.4% | Highest Seebeck coefficient of base-metal types |
| Thermocouple — Base | Type N (Nicrosil / Nisil) | -270 to +1300 °C | Special: ±1.1 °C or 0.4% | Improved long-term drift vs Type K |
| Thermocouple — Noble | Type R (Pt-13Rh / Pt) | -50 to +1768 °C | Special: ±0.6 °C or 0.1% | Oxidizing/inert; high temperature |
| Thermocouple — Noble | Type S (Pt-10Rh / Pt) | -50 to +1768 °C | Special: ±0.6 °C or 0.1% | Defining standard above 962 °C historically |
| Thermocouple — Refractory | Type B (Pt-30Rh / Pt-6Rh) | +50 to +1820 °C | Special: ±0.25% | No cold-junction compensation below 50 °C |
ITS-90 Fixed Points & Common Calibration Setpoints
The International Temperature Scale of 1990 is realized at metrologically defined phase-transition temperatures. The table below summarizes the fixed points routinely realized in our laboratory together with the most commonly requested comparison setpoints. Custom setpoints anywhere in our published range are available on request.
| Setpoint | Defining Substance / Reference | Realization Method | Typical Use |
|---|---|---|---|
| -196.000 °C | Boiling point of liquid nitrogen (1 atm) | LN₂ comparison bath, multi-sensor immersion | Cryogenic RTD and Type T / E / K low-end |
| 0.010 °C | Triple point of water (TPW) — ITS-90 defining fixed point | TPW cell with maintenance bath | Primary reference; SPRT and Class A RTD anchoring |
| 0 °C | Ice point (water/ice equilibrium) | Stirred ice bath, working reference | Routine RTD and thermocouple ice-point check |
| 100.000 °C | Steam point / boiling water | Comparison in stirred fluid bath against SPRT | Pharmaceutical and laboratory RTD validation |
| 231.928 °C | Freezing point of tin — ITS-90 defining fixed point | Tin freeze-point cell, plateau realization | SPRT and reference RTD characterization |
| 232 °C | Tin point comparison setpoint | Comparison in salt or oil bath | Industrial RTD / thermocouple mid-range check |
| 419.527 °C | Freezing point of zinc — ITS-90 defining fixed point | Zinc freeze-point cell, plateau realization | SPRT characterization, Type N / K reference points |
| 660.323 °C | Freezing point of aluminum — ITS-90 defining fixed point | Aluminum freeze-point cell, plateau realization | High-temperature SPRT and noble-TC reference |
| 961.78 °C | Freezing point of silver — ITS-90 defining fixed point | Silver freeze-point cell, plateau realization | Boundary between SPRT and noble-TC scales |
| 1084.62 °C | Freezing point of copper — ITS-90 defining fixed point | Copper freeze-point cell, plateau realization | Noble-thermocouple high-temperature characterization |
| 1085 °C | Copper point comparison setpoint | Tube-furnace comparison against Type R / S / B | Furnace-process and refractory thermocouple cal |
| 1300 – 1700 °C | Tube furnace, refractory reference thermocouples | Comparison against Type B reference | Heat-treat, glass, ceramic, and refractory processes |
About ITS-90
The International Temperature Scale of 1990 is the metrological scale adopted by the 18th General Conference on Weights and Measures. It is realized between 13.8033 K (the triple point of equilibrium hydrogen) and the freezing point of silver using Standard Platinum Resistance Thermometers, and above the silver point using radiation thermometry referenced to a defining fixed point. Industrial calibrations performed in our laboratory propagate uncertainty from this scale through documented working standards.
What You Receive With Every Calibration
Each calibrated sensor is returned with a complete documentation package designed to satisfy aerospace, pharmaceutical, nuclear, and FDA-regulated record-retention requirements. The certificate of calibration is uniquely numbered, signed by an authorized metrology technician, and tied to a serialized record in our quality management system.
For sensors received for re-calibration, both as-found data (the unit's behavior on arrival, before any adjustment) and as-left data (the unit's behavior after any cleaning, repair, or trim) are reported. This enables a customer's calibration program to quantify drift between intervals, optimize the calibration interval itself, and demonstrate sensor health for audit purposes.
Anatomy of an Uncertainty Budget
Every certificate of calibration reports an expanded uncertainty (U = k·uc, typically with coverage factor k = 2 corresponding to approximately 95% confidence). The expanded uncertainty is derived by combining the individual variance contributions of every meaningful error source in the calibration. A representative budget for a Class A PT100 calibrated at the tin point is illustrated below.
| Uncertainty Component | Source / Description | Typical u (mK) | Distribution |
|---|---|---|---|
| Reference standard | Calibration uncertainty of the SPRT itself (carried from NIST) | 1.5 | Normal |
| Reference resistance bridge | Bridge accuracy, linearity, ratio non-self-calibration | 0.8 | Rectangular |
| Bath / furnace stability | Short-term setpoint fluctuation during plateau | 2.0 | Rectangular |
| Bath / furnace uniformity | Vertical and radial gradient at the immersion depth | 3.0 | Rectangular |
| Immersion / stem conduction | Heat conduction along the sensor sheath to ambient | 2.5 | Rectangular |
| Self-heating of the UUT | I²R dissipation in the platinum element under measurement current | 4.0 | Rectangular |
| Drift of reference standard | Allowance for SPRT drift since last NIST calibration | 2.0 | Rectangular |
| Repeatability of UUT | Standard deviation of the mean of replicate readings | 3.0 | Normal |
| Combined uc | RSS of components above | ~7.4 | — |
| Expanded U (k = 2) | Reported as ±U on the certificate | ~15 | — |
Representative values; actual budgets are computed per-calibration and reflect the specific setpoint, reference standard, and unit under test. Lower uncertainty is achievable for fixed-point calibrations of SPRTs and primary reference instruments.
Lead Times That Match the Production Floor
We understand that a sensor pulled for calibration is a sensor missing from a process. Our standard calibration turnaround is 5–7 business days from receipt. Rush and same-day options are available on request for AOG (aircraft-on-ground), critical process outages, and clinical-validation deadlines.
The Unbroken Chain to NIST
Metrological traceability is the property of a measurement result whereby it can be related to a stated reference through a documented, unbroken chain of calibrations, each contributing to the measurement uncertainty. Every sensor calibrated by Thermometrics is traceable through the chain below.
Six Decades of Temperature Metrology Expertise
Calibration is more than running a sensor through a bath. It is the synthesis of an unbroken traceability chain, a controlled laboratory environment, validated methods, trained technicians, and a quality management system that holds every record. Customers who trust us with their reference instruments cite the reasons below.
AS9100D & ISO 9001:2015
Our calibration laboratory operates under the same quality management system that governs our aerospace sensor manufacturing. Every certificate is generated from a controlled record in our QMS.
Same-Day Capability
Our metrology technicians work two shifts. For AOG, clinical, and critical-process outages we routinely receive a sensor in the morning and ship it certificated the same afternoon.
Multi-Industry Acceptance
Our certificates are accepted by FAA Part 145 repair stations, FDA-regulated pharmaceutical manufacturers, Department of Energy facilities, and major aerospace primes worldwide.
Full -196 to +1700 °C Range
One laboratory, one quality system — from liquid-nitrogen cryogenics through silver- and copper-point realization and into refractory thermocouple comparison. No subcontracting required.
Calibration-Interval Management
For fleets and laboratories, we maintain a recall schedule, notify your team in advance of due dates, and coordinate shipping logistics. One less program to staff internally.
Manufacturer-Independent
We calibrate sensors from any manufacturer, not only our own. Field-returned probes, third-party RTDs, and customer-supplied thermocouples are welcomed and processed under the same procedures.
Engineering Support Is Part of the Service
Beyond the certificate itself, our metrology engineers are available to help you design a calibration program: choose the right interval, identify drift patterns across a fleet, select the optimal sensor type for a new application, and write the calibration procedure that satisfies your auditor. There is no charge for application-engineering conversations on quoted work.
- Calibration-interval analysis based on historical drift
- Procedure development for regulated environments
- Uncertainty budget review for customer-internal labs
- Sensor-selection guidance for new measurement points
Ready to Get
Started?
Whether you need a single calibration certificate, a custom-engineered sensor assembly, or a full prototype qualification campaign, our technical team responds to every request within one business day.