--- title: "Data acquisition block diagram and DCS advantages" subject: "Digital Control System" chapter: 1 key: "semester_6/digital_control_system:data-acquisition-advantages" source: https://www.bctengineer.com/q/semester_6/digital_control_system/data-acquisition-advantages site: BCT Engineering --- # Data acquisition block diagram and DCS advantages Digital Control System · Chapter 1: Introduction to Discrete Time Control System - Asked in: 2070 Magh, 6+2 marks - Video: [data acquisition system | data acquisition system in hindi | block diagram | integration in iot |das](https://www.youtube.com/watch?v=MJ2PwmHxpv0) — Mind of Engineer - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/digital_control_system/data-acquisition-advantages - Whole chapter: https://www.bctengineer.com/md/semester_6/digital_control_system/chapter-1 ## Question Explain data acquisition system with its block diagram representation. Also state advantages of digital control system. ## Short answer Data acquisition system collects sensor signals through amplifiers, LPF, multiplexer, S/H, and ADC, scanning all channels each sampling period. Digital control advantages: flexible reprogramming, high accuracy, noise immunity, easy complex algorithms, multi-loop sharing, easy storage and networking. ## Answer #### Data acquisition system A **data acquisition system** collects analog signals from sensors in the plant, conditions them and converts them into digital numbers that the computer can process. ```text Sensor1 -> Amp -> LPF --+ Sensor2 -> Amp -> LPF --+--> Analog -> S/H -> A/D -> CPU Sensor3 -> Amp -> LPF --+ MUX ^ ^ | | | +-------+------+ | Timing and control ``` 1. **Transducers:** convert physical quantities (temperature, pressure, speed) into electrical signals. 2. **Amplifier/signal conditioner:** raises millivolt-level signals to the ADC range, provides isolation and rejects common-mode noise. 3. **Low-pass (anti-aliasing) filter:** removes high-frequency noise and limits the bandwidth below $\omega_s/2$. 4. **Analog multiplexer:** connects the channels one by one to a single S/H and ADC, so one converter serves many inputs. 5. **Sample-and-hold:** samples the selected signal at the sampling instant and keeps it steady during conversion. 6. **A/D converter:** quantizes and codes the value into an n-bit word. 7. **Timing and control:** selects the channel, gives sample/hold and start-of-conversion commands, and tells the computer when data are ready. **Operation:** in every sampling period the channels are scanned in turn; each is sampled, held, converted and stored in memory. The computer then runs the control algorithm. **Example:** a water treatment plant scans pH, turbidity and flow sensors through one 12-bit multiplexed ADC every second. #### Advantages of digital control system - **Flexible:** control law changed by reprogramming, not rewiring. - **Accurate and drift-free:** no change with temperature or ageing of components. - **Better noise immunity** of digital signals. - **Complex/adaptive/nonlinear control** is easy to implement in software. - **One computer serves many loops** (time sharing), so cost per loop is low. - **Easy data storage, display, alarms and networking.** - **Smaller, cheaper, more reliable** hardware. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does the amplifier/signal conditioner do? A. Raises millivolt-level signals to the ADC range, provides isolation and rejects common-mode noise B. Samples the signal C. Converts binary to analog D. Selects channels Answer: A. Conditioning matches the sensor signal to the ADC input range and rejects noise. (Key point: Amplifier functions) 2. What does the analog multiplexer allow? A. Several ADCs to serve one channel B. One S/H and ADC to serve many inputs by connecting channels one by one C. Digital filtering D. D/A conversion Answer: B. Channels are time-shared on a single S/H and ADC. (Key point: Multiplexer purpose) 3. Which is a task of the timing and control block? A. Quantizing the voltage B. Tell the computer when data are ready, and give sample/hold and start-of-conversion commands C. Amplify sensor outputs D. Run the PID law Answer: B. It selects the channel, issues commands and signals data ready. (Key point: Timing and control block) 4. Why is digital control better in noise immunity? A. Digital signals are binary and less affected by noise and interference than analog voltages B. It uses larger voltages C. It has no wires D. It filters everything Answer: A. Binary levels are robust against small disturbances. 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