Home/Industry News/Metrology & Standards
For infrared temperature measurements to be reliable, the measurement values must be traceable step-by-step to national standards. This chain of traceability is underpinned by a set of metrological specifications: blackbody radiation source calibration follows JJF 1552-2015, thermal imager calibration follows JJF 1187-2008, and working radiation thermometer verification follows JJG 856-2015. Understanding these specifications clarifies the "why, what, and how often" of calibration.
Infrared temperature measurement is non-contact, and readings are influenced by multiple factors including target emissivity, distance, ambient radiation, and equipment drift. Without traceability, data from two instruments or two laboratories cannot be compared, let alone used for quality assessment. Traceability links your measurement values, through a series of calibrated standards, ultimately to national metrological primary standards.
For infrared, the key "transfer standard" in this chain is the standard blackbody radiation source—it outputs known, controllable, high-emissivity radiation, serving as the temperature reference for thermal imagers and radiation thermometers.
In infrared metrology, "calibration" and "verification" are often confused, but they have different legal meanings: Verification (JJG) is mandatory legal metrology that issues a pass/fail determination; Calibration (JJF) assesses the deviation of displayed values without a compliance verdict. For infrared equipment:
| Specification | Subject | Scope (Public Information) |
|---|---|---|
| JJF 1552-2015 | Blackbody radiation sources for radiation thermometry | Calibrates the effective brightness temperature of a blackbody, involving emissivity settings, temperature stability, and uniformity (for the −10°C to 200°C range) |
| JJF 1187-2008 | Thermal imagers | Calibration specification for thermal imagers, including parameters like indication error and temperature measurement consistency |
| JJG 856-2015 | Working radiation thermometers | Mandatory verification regulation applicable to a broad temperature range; excludes ear/forehead thermometers and contact types |
In summary: your blackbody is calibrated per JJF 1552, your thermal imager is calibrated per JJF 1187, and your working radiation thermometer is verified per JJG 856—the roles are clearly defined. (Please refer to the latest official versions of each specification.)
There is no universal fixed calibration interval; it is typically determined by considering the device's stability, usage intensity, and the requirements of your quality management system. A common practice is annually. Critical metrological scenarios may require shorter intervals. Recalibration should be performed promptly after maintenance, relocation, or if anomalous readings are detected.
Emissivity is one of the largest sources of uncertainty in infrared temperature measurement. A standard blackbody achieves an effective emissivity very close to 1 (e.g., >0.99) through its cavity structure or high-emissivity coating, and this value is verified as a key parameter during calibration. For practical temperature measurement, the emissivity must be set according to the target material; otherwise, a systematic bias will occur.
If the calibration results are to be used for external quality demonstration, customer acceptance, or qualification audits, a calibration report accredited by CNAS is typically required. This signifies that the laboratory has been assessed under the ISO/IEC 17025 system, ensuring traceable values and a formal evaluation of measurement uncertainty. Internal company calibrations may not bear the CNAS mark, but their results are generally not directly accepted by third parties.
There is no single fixed interval. It depends on the device's stability, usage intensity, and the requirements of your quality management system. Common practice is annually. Recalibration should also be performed after maintenance, relocation, or if anomalous readings occur.
Verification (JJG) is mandatory legal metrology that determines pass/fail compliance. Calibration (JJF) assesses the deviation of displayed values without a compliance verdict. Infrared blackbodies and thermal imagers follow calibration specifications, while working radiation thermometers follow verification regulations.
A standard blackbody achieves an effective emissivity very close to 1 (e.g., >0.99) through its cavity structure or high-emissivity coating, and this is verified during calibration. For practical temperature measurement, the emissivity must be set according to the target material; otherwise, systematic errors will occur.
Use a calibrated standard blackbody as a transfer standard to link the readings of your thermal imager or radiation thermometer step-by-step to a higher-level standard, ultimately tracing to the national radiometric temperature primary standard. Every level in this chain must have a valid calibration/verification certificate.
For external quality demonstration or customer acceptance, a CNAS-accredited calibration report is typically required. This signifies that the laboratory has been assessed under the ISO/IEC 17025 system, with traceable values and a stated measurement uncertainty. Internal company calibrations may not bear the CNAS mark, but their results are generally not directly accepted by third parties.
IES provides both High-Precision Blackbody Radiation Sources and Infrared Test Systems, and supports metrological traceability—integrating "reference source + test platform + value traceability" into a single chain. This helps laboratories and production lines establish a traceable infrared temperature measurement baseline.
This article is a compilation and interpretation of industry news, citing data and viewpoints from public sources with attribution. Market data marked as estimates or projections may vary by source; primary reports should be referred to for accuracy. This document does not constitute investment or procurement advice.