Thermal Imaging Camera Calibration: When and Why It Is Needed

What Happens During Thermal Imaging Camera Calibration?

Thermal imaging cameras (also called infrared (IR) cameras or thermographic cameras), measure surface temperatures without contact by detecting the infrared radiation emitted by objects. Like any precision measurement instrument, their detectors and optical systems drift over time due to thermal cycling, humidity exposure, mechanical vibration, and normal component ageing. Calibration is the process of comparing the camera's output against a known reference to quantify and document this drift.

During a laboratory calibration, the technician mounts the camera on a stable stand and directs it at a blackbody radiation source. A device that emits infrared radiation with a precisely known, uniform temperature and an emissivity close to 1.00. The blackbody is stabilised at a series of temperature setpoints across the camera's specified measurement range. At each setpoint, the camera's displayed temperature reading is recorded and compared against the reference blackbody temperature (verified by a traceable contact thermometer or RTD sensor). The difference between the camera's reading and the true temperature is the calibration error at that point.

A typical calibration for an industrial thermal camera covers at least five temperature points (for example 30°C, 60°C, 100°C, 200°C, and 300°C), though the exact range depends on your camera's specification and how you use it. The technician then calculates the expanded measurement uncertainty for the entire calibration process, accounting for the uncertainty of the reference blackbody, the contact thermometer, environmental conditions, and the camera's own resolution. This uncertainty value (expressed at a confidence level of 95% (coverage factor k=2)), is a mandatory element of any ISO/IEC 17025 compliant calibration certificate.

What Measurements Are Made and Which Reference Standards Apply?

The core measurement made during thermal camera calibration is temperature, specifically the apparent surface temperature in degrees Celsius (°C). The measurement traceability chain runs from your camera, through our working standard blackbody, through our reference standard thermometry equipment, and ultimately to the International Temperature Scale of 1990 (ITS-90) as realised by Singapore's National Metrology Centre (NMC) at A*STAR.

At Unitest Instruments, our reference equipment and calibration procedures are independently assessed under SAC-SINGLAS accreditation no. LA-2023-0845-C, issued by the Singapore Accreditation Council (SAC). This means every calibration we perform carries formal traceability accepted by Singapore's regulatory bodies, international auditors, and ISO 9001 quality management systems.

Key reference standards used

• Calibrated blackbody radiation source: emissivity ≥0.95, temperature stability ±0.1°C or better, traceable to NMC Singapore.
• Reference platinum resistance thermometer (PRT) or calibrated thermocouple: traceable to ITS-90 via NMC.
• Ambient condition monitoring: laboratory temperature maintained at 23°C ±2°C, relative humidity 45–70% RH to minimise atmospheric absorption errors.
• Calibration procedure: aligned with EURAMET cg-13 (Guidelines on the Determination of Uncertainty in Gravimetric Volume Calibration) adapted for radiation thermometry, and ASTM E1292 (Standard Guide for Measurement and Calculation of Emissivity).

The result of the calibration is documented on a calibration certificate that is fully traceable to SI units. To understand what makes a calibration certificate legally and technically valid, see our detailed guide: What a Calibration Certificate Must Show, and What to Look For.

Singapore Regulatory Context: Who Requires Thermal Camera Calibration?

Singapore's regulatory landscape creates clear requirements for calibrated thermal imaging instruments in several sectors. Understanding which agency's requirements apply to your use case determines how rigorous your calibration documentation needs to be.

Workplace Safety and Health (WSH). MOM

The Ministry of Manpower's Workplace Safety and Health framework, administered under the WSH Act, requires employers to maintain safe working environments and use properly maintained measurement equipment for hazard identification. Thermal imaging cameras are widely used for electrical panel thermography. A preventive maintenance method that identifies overheating connections and components before they cause fires. Thermographic inspections carried out for WSH compliance purposes, insurance surveys, or fire safety audits should use a calibrated camera to ensure that reported temperature anomalies are accurate and legally defensible. Uncalibrated readings could either miss a genuine fault (false negative) or trigger a costly unnecessary shutdown (false positive).

Building and Construction Authority (BCA)

Infrared thermography is an approved non-destructive testing method for building envelope inspections. Detecting thermal bridges, moisture ingress, and insulation defects in facades and roofs. BCA-related inspections, particularly for Green Mark certification or building defects assessment, require thermographic surveys to be conducted with calibrated equipment. The inspection report is expected to reference the instrument's calibration status.

Singapore Food Agency (SFA) and Cold-Chain Applications

Non-contact thermal cameras used in food processing or cold-chain temperature monitoring must be calibrated to ensure compliance with SFA's food safety temperature requirements. Where a thermal camera is part of a HACCP (Hazard Analysis Critical Control Point) plan, the calibration record forms part of the HACCP documentation and is subject to audit.

Health Sciences Authority (HSA) and Pharmaceutical

Pharmaceutical manufacturers and medical device companies operating under HSA Good Manufacturing Practice (GMP) guidelines or ISO 13485 are required to calibrate all measurement equipment used in product quality decisions. Thermal cameras used in process monitoring, environmental monitoring, or equipment qualification fall into this category.

Calibration Interval Recommendations

How often you calibrate your thermal imaging camera depends on how it is used, the regulatory requirements that apply, and the consequences of a measurement error. There is no universal rule that fits every application, but the following framework covers the most common scenarios in Singapore.

The standard recommendation is a 12-month calibration interval for cameras used in industrial preventive maintenance, quality assurance, or regulatory compliance. This aligns with ISO 9001 requirements and is the default accepted by most Singapore regulatory auditors. For guidance on setting the right interval for your instruments generally, see our article on How Often Should You Calibrate Your Instruments?

What a Proper Thermal Camera Calibration Certificate Must Show

Not all calibration certificates are created equal. A certificate that does not meet ISO/IEC 17025 requirements may be rejected by your quality auditor or regulatory inspector, leaving you with an instrument whose accuracy is legally unverifiable. Here is what to look for.

Mandatory elements on an ISO/IEC 17025 compliant certificate

• Instrument identification: make, model, serial number, and asset tag if applicable.
• Calibration date and the date the next calibration is due.
• Laboratory identification: name, address, and SAC-SINGLAS accreditation number (e.g. LA-2023-0845-C).
• Reference standard used and its traceability statement (traceable to NMC Singapore / ITS-90).
• Calibration results table: nominal temperature setpoint, camera's measured value, and the calibration error at each point.
• Expanded measurement uncertainty at k=2 (95% confidence level). This is mandatory under ISO/IEC 17025:2017 and its absence means the certificate is non-compliant.
• Environmental conditions during calibration (ambient temperature and humidity).
• Authorised signatory. The calibration engineer's name and signature or equivalent electronic authorisation.
• Statement of conformity (pass/fail against a specification), if requested. Note that this is separate from the measurement results and must reference the specification used.

For a full breakdown of what each element means and how to read an uncertainty statement, see our article Calibration Certificate Explained: What Every Field on the Document Means.

Accredited vs Non-Accredited Calibration for Thermal Cameras

Singapore has a significant number of calibration service providers, but not all hold SAC-SINGLAS accreditation for thermal/radiometric temperature calibration. The distinction matters enormously in practice.

Accredited calibration (SAC-SINGLAS, traceable to NMC Singapore) means an independent body has assessed the laboratory's technical competence, equipment, staff qualifications, and measurement uncertainty claims against ISO/IEC 17025. The accreditation scope defines exactly which measurements the laboratory is permitted to issue traceable certificates for. Unitest Instruments holds SAC-SINGLAS accreditation no. LA-2023-0845-C covering temperature calibration.

Non-accredited calibration may involve a capable technician with adequate equipment, but there is no third-party verification of the laboratory's claims. The certificate cannot be formally accepted as evidence of traceability by ISO 9001 auditors, WSH inspectors, BCA assessors, or HSA GMP auditors. For applications where the measurement outcome affects safety, quality, or regulatory compliance, non-accredited calibration is not an adequate substitute.

To understand the full legal and technical implications of this distinction, read our guide: Accredited vs Non-Accredited Calibration: What the Difference Means for Your Business.

Purchasing vs Calibrating: Getting the Most from Your Thermal Camera

If you are in the market for a thermal imaging camera for industrial or compliance use in Singapore, the purchase decision and the calibration plan should be made together. A camera with a wider temperature range, finer resolution detector (e.g. 640×480 vs 160×120), and lower noise-equivalent temperature difference (NETD) will typically achieve tighter calibration uncertainty. Meaning your measurements will be more reliable and your calibration certificate will show smaller errors.

Leading brands such as FLIR, Hikmicro, Fluke, and Testo all produce cameras that can be calibrated under SAC-SINGLAS accredited conditions. However, the camera must be sent to the calibration laboratory. Calibration is not something that can be performed adequately by scanning a QR code or running an internal self-test routine. Self-test or "internal calibration" modes on modern cameras are non-uniformity corrections (NUC) that improve image uniformity; they are not a substitute for a formal traceable calibration against a reference blackbody.

You can explore a wide range of calibrated thermal imaging cameras and related test equipment at unitestshop.com. When you purchase from Unitest, our team can advise on the appropriate calibration schedule and get your instrument into our calibration workflow immediately, so you have a valid certificate before you put the camera into service.

Why Calibration Verifies the Hardware, Not Your Field Settings

A subtlety that catches out many thermal camera owners: a calibration certificate confirms that the camera's detector and internal electronics correctly convert incoming infrared radiation into a temperature reading under known, controlled conditions. It does not, and cannot, verify that the emissivity, reflected temperature, and distance settings you enter in the field on a specific job are correct for that specific target. Both factors matter independently, and confusing them is a genuine source of measurement error even on a freshly, correctly calibrated camera.

During laboratory calibration, the blackbody source's emissivity is precisely known (typically 0.95 to 1.00) and the camera is set to match it exactly, which is what allows the calibration to isolate and quantify the camera's own hardware error. In the field, the technician is responsible for correctly estimating and entering the emissivity of the actual target surface, which varies enormously between materials, painted metal at roughly 0.90-0.95, bare polished aluminium as low as 0.05-0.20, as covered in more depth in our companion buying guide on industrial infrared thermometers. A calibrated camera with an incorrectly entered emissivity setting will produce a confidently displayed but genuinely wrong temperature reading, and no amount of hardware accuracy compensates for this operator input error. This is precisely why a competent thermography programme trains technicians on both disciplines together: the instrument's calibration status establishes that the hardware itself is trustworthy, and separate field technique training establishes that the technician is applying it correctly to the actual target in front of them.

Detector Types and Why They Calibrate Differently

Not all thermal camera detectors behave identically during calibration, and understanding the two main detector technologies in commercial use helps explain why some cameras drift faster than others and why calibration intervals sometimes need adjusting from the standard 12-month baseline.

The overwhelming majority of industrial and commercial thermal cameras, including most FLIR, Hikmicro, Fluke, and Testo models, use uncooled microbolometer detectors: an array of thousands of tiny elements that change electrical resistance in response to incident infrared radiation. These are robust, relatively affordable, and require no active cooling, but they are more susceptible to drift from ambient temperature changes and mechanical shock than the alternative. Cooled detector cameras, using a cryogenically cooled photon detector, are found in specialist high-performance applications (military, certain scientific and R&D uses) and offer superior sensitivity and stability, but at substantially higher cost and with additional maintenance requirements for the cooling system itself, and are rarely encountered in Singapore's typical industrial and commercial thermography applications.

For the microbolometer cameras that make up the vast majority of Singapore's installed base, the built-in Non-Uniformity Correction (NUC) function, triggered automatically or manually via a mechanical shutter cycling in front of the detector, corrects pixel-to-pixel variation in real time during use, but this is a self-referencing internal correction, not a calibration against an external, independently traceable standard, and should not be confused with the formal blackbody calibration process described above. A camera that performs a NUC cycle correctly and produces a visually uniform image can still be measuring absolute temperature incorrectly if its underlying calibration coefficients have drifted, which is exactly the gap that periodic accredited calibration exists to catch.

Storing and Transporting Cameras Between Calibrations

How a thermal camera is stored and transported between calibration visits meaningfully affects how long it holds its accuracy, and a few straightforward practices reduce the chance of an unexpected out-of-tolerance finding at the next scheduled calibration. Temperature-controlled storage, avoiding leaving the camera in a vehicle exposed to direct tropical sun (where cabin temperatures in Singapore routinely exceed 50°C) protects the detector array from thermal stress well beyond its normal operating range. Physical protection during transport, using the manufacturer's padded case rather than a loose tool bag, prevents the mechanical shock that is a leading cause of detector misalignment and lens damage, both of which show up as calibration drift or, in severe cases, an outright fault requiring repair before recalibration can even be attempted. For facilities running a fleet of thermal cameras across multiple technicians, building these handling practices into a simple, shared care standard, rather than leaving it to individual habit, measurably reduces the frequency of out-of-tolerance findings and unplanned repair costs across the fleet's operating life.