EC-8.2 Calibration, Traceability and Propagating Error
You can say what a calibration certificate promises and under what conditions, separate a systematic error from a random one, carry an uncertainty through a calculation, and report a result with a figure count that is not a fiction.
Before:S4-5. Probability Theory & Stochastic ProcessesPE2-4. Sensing Techniques and Sensor SystemsEC-1. Circuit AnalysisUnlocks:EC-13. Laboratory Practice, in Sequence
A reading with no uncertainty attached is not a measurement, it is a number. This topic is what turns one into the other, and it is the reason the laboratory modules later can ask whether two results actually differ. It also settles the most common piece of misplaced confidence in engineering work, which is reporting six figures from an instrument that guarantees three.
Work through these
What calibration is, and what it is not
Calibration compares an instrument against a better one and records the difference. It does not make the instrument correct, and an instrument can be perfectly calibrated and still be the wrong instrument for your measurement.
NPTEL: Electrical Measurement and Electronic Instruments (IIT Kharagpur) · CourseTraceability, and the chain back to a standard
Every honest measurement can be followed through a chain of comparisons to a national or international standard. Each link adds uncertainty, so the chain is short on purpose and every step in it is recorded.
NPTEL: Measurement and Instrumentation (IIT Guwahati) · CourseSystematic error and random error, separated
Random error moves your readings around and shrinks when you average. Systematic error moves all of them the same way and averaging does nothing to it, which is why the two must be found and reported separately.
NPTEL: Measurement and Instrumentation (IIT Guwahati) · CoursePropagating uncertainty through a calculation
When a result is computed from several measured quantities, each carries its uncertainty into the answer. For a sum the absolute uncertainties combine; for a product or ratio the relative ones do, which usually makes one input dominate.
NPTEL: Measurement and Instrumentation (IIT Guwahati) · CourseSignificant figures, and reporting a result honestly
The uncertainty decides the figure count, not the display. If the uncertainty is in the second decimal place, the third and fourth decimal places are noise dressed as precision and should not be written down.
NPTEL: Electrical Measurement and Electronic Instruments (IIT Kharagpur) · CourseDrift, warm-up and the conditions a calibration assumes
A certificate holds at a stated temperature, after a stated warm-up, for a stated interval. Outside any of those the numbers are an estimate, and drift over months is the usual reason an instrument quietly stops agreeing with itself.
NPTEL: Electrical Measurement and Electronic Instruments (IIT Kharagpur) · Course
Sign in to keep your progress.
Free resources
We haven't checked most of these for screen reader use yet.
Links last checked 3 Sept 2026.
Stuck here?
Ask a mentor. A real person answers, and they can see exactly which topic you're on. Usually within a couple of working days.
Checking your session…
Topics shown in module order.