Jawaharlal Nehru Technological University Hyderabad B.Tech IV Year SENSORS AND TRANSDUCERS Previous Question Paper (July/August - 2022 - R16)

The main functions of instruments and measurement systems are categorized as follows:

1. Indicating function: This function provides a visual representation of the measured quantity, typically through a pointer moving over a calibrated scale or a digital display. It allows the user to observe the instantaneous value of the variable being measured.
2. Recording function: This function involves creating a permanent record of the measured variable over time. This is achieved using devices like chart recorders, magnetic tapes, or digital data loggers, which allow for the analysis of trends and historical data.
3. Controlling function: This function uses the output of the measurement system to regulate the process variable. The measured value is compared against a set point, and an error signal is generated to drive a controller (such as a valve or switch) to maintain the process within desired limits.

A generalized measurement system consists of several functional elements that process the input signal to provide a usable output. The elements are arranged in the following sequence:

1. Primary Sensing Element: This element detects the physical variable (e.g., temperature, pressure) and converts it into a usable electrical or mechanical signal.
2. Variable Conversion Element: This stage converts the output of the primary sensor into a more suitable form, such as changing a mechanical displacement into an electrical voltage.
3. Variable Manipulation Element: This element modifies the signal to improve its quality or magnitude, often through amplification, filtering, or impedance matching, without changing the information content.
4. Data Transmission Element: This is required when the elements of the system are physically separated. It transmits the signal from one location to another using cables, telemetry, or wireless links.
5. Data Presentation Element: This is the final stage where the information is displayed for human observation. This includes indicators, recorders, or computer interfaces that provide the final measured value.

In summary, the signal flows from the Primary Sensing Element through the Conversion, Manipulation, and Transmission stages before reaching the Data Presentation unit.