JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year ELECTRONIC MEASUREMENTS AND INSTRUMENTATION Previous Question Paper (August - 2022 - R18)

A generalized measuring system consists of three main stages: the input stage, the signal conditioning stage, and the output stage. The block diagram follows the sequence: Primary Sensing Element → Variable Conversion Element → Variable Manipulation Element → Data Transmission Element → Data Presentation Element.

1. Primary Sensing Element: Detects the physical quantity (measurand) and converts it into a usable electrical or mechanical signal.
2. Variable Conversion Element: Converts the output of the sensor into a more suitable variable, such as changing a displacement into a voltage.
3. Variable Manipulation Element: Processes the signal to improve its quality, including amplification, filtering, or attenuation.
4. Data Transmission Element: Transmits the signal from one location to another, often requiring modulation or impedance matching.
5. Data Presentation Element: Provides the final output in a readable format, such as a digital display, recorder, or computer interface.

Static characteristics describe the performance of an instrument when measuring a constant input that does not change over time. Key characteristics include:

• Accuracy: The closeness of the measured value to the true value of the quantity.
• Precision: The degree of reproducibility of a set of measurements; a measure of the consistency of results.
• Sensitivity: The ratio of the change in output to the change in input, defined as
  S = ΔOutput / ΔInput
  .
• Resolution: The smallest change in the input that produces a detectable change in the output.
• Linearity: The ability of the instrument to maintain a constant proportionality between input and output across its operating range.
• Hysteresis: The difference in output for the same input when approached from increasing versus decreasing directions.
• Drift: The variation in output over time for a constant input due to environmental factors like temperature or aging.
• Threshold: The minimum input value required to produce a detectable output.