---
title: "Static and dynamic performance parameters"
subject: "Instrumentation I"
chapter: 2
key: "semester_4/instrumentation_i:static-dynamic-performance-parameters"
source: https://www.bctengineer.com/q/semester_4/instrumentation_i/static-dynamic-performance-parameters
site: BCT Engineering
---

# Static and dynamic performance parameters

Instrumentation I · Chapter 2: Theory of measurement

- Asked in: year not given, 8 marks
- Video: [STATIC AND DYNAMIC CHARACTERISTICS OF MEASURING INSTRUMENTS | Static vs Dynamic characteristics](https://www.youtube.com/watch?v=78NpGnA1sX4) — Shriji Informatrix
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/instrumentation_i/static-dynamic-performance-parameters
- Whole chapter: https://www.bctengineer.com/md/semester_4/instrumentation_i/chapter-2

## Question

Differentiate between static and dynamic performance parameters. Also explain different types of static and dynamic performance parameters.

## Short answer

Static characteristics describe performance with constant or slowly varying inputs: accuracy, precision, sensitivity, linearity, hysteresis. Dynamic characteristics describe response to time-varying inputs: speed of response, measuring lag, fidelity, bandwidth, and time constant.

## Answer

**Static characteristics** describe an instrument's performance when the input is constant or changes very slowly. **Dynamic characteristics** describe its response when the input changes with time.

| Point | Static | Dynamic |
|---|---|---|
| Input | Constant or slowly varying | Rapidly varying with time |
| Describes | Steady-state behaviour | Transient and frequency behaviour |
| Examples | Accuracy, precision, sensitivity | Speed of response, lag, fidelity |
| Mathematics | Algebraic equations | Differential equations |

#### Static parameters
- **Accuracy:** closeness of the measured value to the true value.
- **Precision:** closeness of repeated readings to each other (reproducibility).
- **Resolution:** smallest change in input that gives a detectable change in output.
- **Sensitivity:** change in output per unit change in input (Δo/Δi).
- **Linearity:** how closely the calibration curve is a straight line; expressed as a percentage of full scale.
- **Threshold:** minimum input needed to start any output change from zero.
- **Hysteresis:** different outputs for the same input depending on direction of change.
- **Drift:** change in output with no change in input (zero drift, span drift).
- **Range and span:** limits of input the instrument can measure; span = max − min.
- **Dead zone / dead band:** range of input where there is no output change.
- **Repeatability and reproducibility, stability, tolerance.**

#### Dynamic parameters
- **Speed of response:** how quickly the instrument responds to a change in input.
- **Measuring lag:** delay in response; retardation type (immediate but slow response) and time-delay type (response starts after a dead time).
- **Fidelity:** ability to reproduce the input waveform without distortion.
- **Dynamic error:** difference between the true value and the indicated value when the input changes with time.
- **Bandwidth and frequency response:** range of input frequencies for which the amplitude ratio stays within limits.
- **Time constant, rise time, settling time, overshoot** for first- and second-order systems.
- **Damping ratio and natural frequency** for second-order systems.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Dynamic characteristics describe the instrument's performance when:
   A. The input is constant
   B. The input changes with time
   C. The input is zero
   D. The instrument is being calibrated only
   Answer: B. Static characteristics apply to constant or slow inputs; dynamic ones to inputs varying with time. (Key point: Static vs dynamic)

2. Precision of an instrument means:
   A. Closeness of the reading to the true value
   B. Smallest detectable input change
   C. Closeness of repeated readings to each other
   D. Change in output per unit input
   Answer: C. Precision is repeatability of readings; accuracy is closeness to the true value. (Key point: Accuracy vs precision)

3. Sensitivity is defined as:
   A. Smallest input change giving a detectable output change
   B. Range of input with no output change
   C. Output change with no input change
   D. Change in output per unit change in input
   Answer: D. Sensitivity = delta output / delta input; resolution is the smallest detectable input change. (Key point: Sensitivity and resolution)

4. In the time-delay type of measuring lag, the response:
   A. Begins only after a dead time following the input change
   B. Starts immediately but is slow
   C. Never settles
   D. Is zero at all frequencies
   Answer: A. Retardation lag responds immediately but slowly; time-delay lag starts after a dead time. (Key point: Measuring lag)

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