When you read a calibration certificate that says "reading: 200.3 bar," what does that number actually tell you on its own? Without knowing the measurement uncertainty, it's an incomplete piece of information. Measurement uncertainty is the range within which the true value of the measured quantity lies, at a stated level of confidence (typically 95%).
Why Is It Often Ignored?
Many equipment users see uncertainty as a complex technical detail they can skip over. But it's exactly what ISO/IEC 17025 requires testing and calibration laboratories to calculate and report — and it's the core difference between an accredited laboratory and an informal visit.
A Concrete Example
Suppose a piece of industrial equipment's specification sets a maximum allowed operating pressure of 200 bar. The reference gauge reports 200.3 bar with an uncertainty of ±0.5 bar. That means the true value could be anywhere from 199.8 to 200.8 bar — in other words, the actual pressure may well exceed the allowed limit. Without accounting for uncertainty, this result would be wrongly read as "acceptable."
Where Does Uncertainty Come From?
Sources of uncertainty include the accuracy of the reference instrument, environmental conditions (temperature, humidity, vibration), operator skill, and the stability of the device under test itself. An accredited calibration laboratory identifies, combines, and accounts for all of these sources in its uncertainty budget, following the international GUM (Guide to the Expression of Uncertainty in Measurement).
What This Means for Our Clients
Every calibration certificate you receive from Persia Azma System includes the measurement uncertainty alongside each result. That means you don't just know what value your device is showing — you know how much you can trust that value. And that's exactly what a sound engineering or clinical decision requires.