Accuracy indicator in static calibration: among dead zone, drift, and static error, identify the measure that directly judges the accuracy of an instrument at a stated operating point.

Introduction / Context:
Instrument accuracy is assessed by how closely the indicated value matches the true value under specified conditions. Several static characteristics influence readings, but only one directly quantifies the deviation at a point in time and input.

Given Data / Assumptions:

• Calibration conditions are steady (no transients).
• Error is defined as indicated value minus true value.
• Repeatability and hysteresis are considered separately.

Concept / Approach:
Static error (bias) = indicated value − true value. This directly expresses accuracy. Dead zone (dead band) describes an insensitivity region where small changes do not alter reading. Drift is the slow change of indication with time when input is constant. Both affect usability but are not the accuracy metric itself at a given point.

Step-by-Step Solution:

Verification / Alternative check:
Calibration certificates report allowable accuracy as ±(percentage of full-scale or of reading), which is a bound on static error.

Why Other Options Are Wrong:

Common Pitfalls:
Equating precision (repeatability) with accuracy; an instrument can be precise yet biased (large static error).

Final Answer:
Static error