ABOUT
Introduction
Furnace calibration is the structured verification process that confirms an industrial furnace or oven maintains accurate, uniform temperatures across its entire working zone under real operating conditions. Tempsens Calibration Centre offers a complete service for furnaces, including both off-the-shelf and on-site calibrations, using a laboratory accredited by National Accreditation Board for Testing and Calibration Laboratories (NABL), and covering temperatures from -80 degrees Celsius to 1200 degrees Celsius.
The calibration framework used at Tempsens complies with the requirements of AMS 2750H/CQI-9, which includes the use of traceable reference instruments to validate thermocouples and calibrated thermocouples. Tempsens ensures that your furnace provides repeatable thermal performance that supports product quality, process integrity, and full regulatory compliance for all types of processes involving heating, melting, forging, and/or sintering while meeting the requirements outlined in this standard.
About Furnace Calibration / Thermal Survey / Temperature Uniformity Survey
Types of Tests for Furnace Calibration
Two standardised tests form the technical core of every furnace calibration service:
Temperature Uniformity Survey (TUS) : A thermal survey that maps heat distribution at multiple positions across the entire furnace work zone using calibrated thermocouples. It identifies hot and cold spots, defines the qualified working volume, and generates objective evidence of temperature uniformity under normal operating conditions. Data collection is sustained for a minimum of 30 minutes post-stabilisation at each test temperature point.
For more information related on how to Calibrate a Furnace Using TUS you can read our technical guide on same.
System Accuracy Test (SAT) : A system accuracy test that quantifies total measurement error within the temperature control loop — including the controller, lead wires, and thermocouple. The SAT verifies that your control system is reading and operating correctly from the point you’ve established for the temperatures, as well as verifying whether or not the furnace produces the heat properly.
Key Components of Furnace Calibration
- Furnace classification (AMS 2750H Class 1–6) determines the tolerance band and minimum sensor count for the temperature uniformity survey
- Multipoint thermocouple placement at centre, corners, edges, and other critical zones within the working chamber, standardised across all requalification cycles
- TUS data logging maintained for a minimum of 30 minutes post-stabilisation per test temperature setpoint
- System accuracy test (SAT) measuring the combined error of the controller, extension lead, and sensor at operating setpoint
- Calibration & Measurement Capability (CMC): ±0.50°C for -80°C to 200°C range; ±5.75°C for >200°C to 1200°C range
- Jack panel inspection with replacement required if older than two years or showing visible degradation, to prevent measurement errors
- Traceable calibration certificates with zone-wise thermal maps and full measurement uncertainty documentation
Benefits and Requirements
- Validated product quality: Confirmed temperature uniformity survey results ensure consistent metallurgical and thermal processing outcomes batch after batch.
- Regulatory compliance: Meets mandatory requirements under AMS 2750H/CQI-9.
- Hot and cold spot detection: TUS finds thermal unevenness before they actually create defects or rejections during processing.
- Verify control system: System accuracy test confirms total loop error is within the tolerance criteria for furnace class.
- Calibration traceability: Calibration records, TUS data and SAT reports make up a complete audit trail for third parties who want to perform a quality audit or verify quality through customer inspections.
- Production flexibility: Multi-temperature TUS data provides performance to establish process planning throughout the entire operation range of the furnace.
Application Areas of Furnace Calibration
- Vacuum furnace calibration essential for aerospace, defence, and precision component heat treatment in controlled or partial-pressure atmospheres.
- Continuous belt furnace uniform throughput temperature critical for electronics, ceramics, and sintering applications.
- Forging furnace confirms billet temperatures meet metallurgical specifications before forming operations.
- Batch furnace documents thermal cycles for castings, stampings, and heat-treated machined components.
- Rotary furnace ensures uniform radial temperature distribution in mineral processing and chemical calcination.
What We Do?
| Quality Measured/Instruments | Temperature Range | Calibration & Measurement Capability |
| Multipoint Position Calibration of Chamber, Oven, Furnaces (Thermal Mapping(TUS) | -80ºC to 200ºC | 0.50ºC |
| >200ºC to 1200ºC | 5.75 ºC |
Why Tempsens for Furnace Calibration Service?
- NABL-accredited calibration laboratory with documented CMC from -80°C to 1200°C, traceable to national standards.
- Our on-site and in-lab furnace calibration services will be provided by skilled technicians utilizing certified reference equipment for calibration purposes.
- Our calibration capabilities encompass vacuum furnace calibration for customers in aerospace, defense, and specialty metals industries, with the addition of an alternative atmosphere protocols (argon/nitrogen) available when there is a risk of contamination from the process.
- 35+ years experience in thermal measurement with industry exposure through our services to over 75 countries.
FAQ
Frequently Asked Questions
Find answers to frequently asked questions related to Furnace Calibration / Thermal Survey / Temperature Uniformity Survey.
Furnace calibration involves two processes: a system accuracy test (SAT), which measures total error in the temperature control loop, and a temperature uniformity survey (TUS), where calibrated thermocouples are placed at defined positions throughout the chamber to verify heat distribution.
Heating element ageing, sensor drift and calibration error occur throughout time and if you do not have a regular thermal survey and SAT verification performed at some point in time, these errors compound becoming a serious safety issue for the operation of the furnace. Regular furnace calibration prevents out-of-spec processing, product rejections, and non-conformances during audits.
Under AMS 2750H/CQI-9, a temperature uniformity survey is typically required quarterly or semi-annually depending on furnace class, while a system accuracy test is required monthly. Frequency also depends on furnace usage intensity and the applicable customer or process standard.
The primary standard is AMS 2750H. Furnaces are classified into Class 1 through Class 6 under AMS 2750H, each with defined temperature uniformity tolerances. Tempsens furnace calibration service supports compliance across all these frameworks.
