Jawaharlal Nehru Technological University Hyderabad B.Tech IV INTRODUCTION TO INSTRUMENTATION Previous Question Paper (February/March - 2022 - R18)

A strip chart recorder is an electromechanical device used to record time-varying signals on a continuous roll of paper. Its basic elements include:

1. Input Signal Conditioning: Amplifies or attenuates the incoming signal to a level suitable for the recording mechanism.
2. Drive Mechanism: A motor-driven system that moves the chart paper at a constant, controlled speed.
3. Recording System: Consists of a pen or stylus attached to a galvanometer or servomotor. The pen deflects across the paper proportional to the magnitude of the input signal.
4. Chart Paper: A continuous strip of grid-marked paper that moves perpendicular to the pen's motion, allowing the signal to be plotted against time.

The sketch involves a roll of paper moving over a platen, with a pen arm pivoting from a central point, controlled by a magnetic field or servo feedback loop to trace the signal variations.

A Digital Storage Oscilloscope (DSO) captures, digitizes, and stores waveforms in memory for analysis. The block diagram consists of an input amplifier, an Analog-to-Digital Converter (ADC), a digital memory unit, a microprocessor, and a display unit (LCD/CRT).

Working Principle:

1. The input signal is conditioned by the amplifier.
2. The ADC samples the signal at high frequency and converts it into digital binary data.
3. This data is stored in the digital memory (RAM).
4. The microprocessor retrieves the data from memory to reconstruct the waveform and displays it on the screen.

Advantages of DSO:

• Waveforms can be stored indefinitely in memory.
• Allows for pre-trigger viewing, capturing events before the trigger point.
• Provides advanced signal processing capabilities like FFT, averaging, and automated measurements.
• Easy interfacing with computers for data logging and analysis.
• High-resolution display with the ability to zoom into specific signal segments.