Measurement record, not an alarm table

Controlled Thermography ΔT and Uncertainty

Calculate a signed target-minus-reference temperature difference and its combined standard uncertainty from a documented quantitative thermography measurement. No universal ISO, NETA, bearing, motor or electrical alarm limits are applied.

ISO 18434 scope statedSigned ΔTStandard uncertaintyNo severity automation

Controlled-input calculation

Do not infer condition severity or an action deadline from ΔT alone. The reference must be technically comparable, and quantitative IRT depends on emissivity, reflected apparent temperature, transmission/attenuation, calibration, spatial resolution, viewing geometry, environment and operating state. Use severity criteria only from the released site procedure, OEM limits and the governing licensed standard.

Target temperature Corrected quantitative surface-temperature result Reference temperature Comparable reference defined below Temperature unit Applies to both values and uncertainties Target standard uncertainty u(Ttarget) Non-negative, k=1-equivalent standard uncertainty in the selected unit Reference standard uncertainty u(Tref) Non-negative, k=1-equivalent standard uncertainty in the selected unit Reference definition Identify point/component, comparability, load/state and acquisition timing Measurement procedure and corrections Record camera/calibration, emissivity, reflected apparent temperature, distance/optics and transmission basis Operating state / load record Record actual load, environmental state and stability — do not extrapolate automatically I confirm that both temperatures are corrected quantitative measurement results and that emissivity, reflected apparent temperature, attenuation/transmission, calibration, spatial resolution, geometry and environmental effects are addressed by the recorded procedure. I confirm that the two uncertainty inputs are standard uncertainties for this model and are sufficiently uncorrelated for root-sum-of-squares combination; covariance is handled elsewhere if this is not true.

Enter a controlled target/reference measurement; no thresholds are preloaded.

Measurement-model result

Signed ΔT = Ttarget − Tref-

Combined standard uncertainty uc(ΔT)-

ΔT − uc(ΔT)-

ΔT + uc(ΔT)-

Model and units

ΔT = Ttarget − Tref
uc(ΔT) = √(u(Ttarget)² + u(Tref)²)

The uncertainty relation is the uncorrelated-input special case of the JCGM law of propagation of uncertainty. Celsius temperature differences and kelvin differences have the same numerical value; Fahrenheit differences and their standard uncertainties are multiplied by 5/9 before combination.

The displayed ΔT ± uc span uses one combined standard uncertainty. It is not automatically a confidence interval, an expanded uncertainty or an alarm band. If target and reference errors are correlated, use the covariance-aware model instead.

Standardenes anvendelsesområde

ISO 18434-1:2008 and ISO 18434-2:2019 provide procedures and guidance for establishing severity assessment criteria; their public ISO descriptions do not establish the six universal component tables formerly shown here.
ISO 18434-1 explicitly addresses reflected apparent temperature, emissivity and attenuating media for quantitative surface-temperature measurement.
ANSI/NETA MTS-2023 is the current published electrical maintenance-testing edition and supersedes MTS-2019. Its exact proprietary table criteria require a licensed copy and the correct reference/load conditions.
No motor insulation class, bearing seizure, coupling alignment, steam-trap loss, fire-risk or shutdown decision is calculated.

Official evidence

ISO 18434-1:2008, Edition 1 (confirmed 2023)

General IRT procedures for machinery condition monitoring; includes guidance on establishing severity criteria and procedures for reflected apparent temperature, emissivity and attenuating media.

ISO 18434-2:2019, Edition 1 (confirmed 2024)

Image interpretation and diagnostics; provides guidance on establishing severity assessment criteria rather than one universal alarm table for every component.

JCGM 100:2008(E), GUM 1995 with minor corrections

Defines combined standard uncertainty and the law of propagation for uncorrelated and correlated input quantities.

ANSI/NETA MTS-2023 official status page

Approved 6 March 2023 and supersedes MTS-2019. The page establishes edition and scope; it does not publicly substantiate the former 10/35/75 °C table.