---
title: "Essential components of a DAQ system"
subject: "Instrumentation II"
chapter: 5
key: "semester_5/instrumentation_ii:daq-components"
source: https://www.bctengineer.com/q/semester_5/instrumentation_ii/daq-components
site: BCT Engineering
---

# Essential components of a DAQ system

Instrumentation II · Chapter 5: Data Acquisition And Transmission

- Asked in: 2071 Chaitra, 4 marks; 2070 Chaitra, 5 marks; 2078 Bhadra, 5 marks (asked 3 times)
- Video: [Data Acquisition System](https://www.youtube.com/watch?v=zv5NXbl00GQ) — WIT Solapur - Professional Learning Community
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/instrumentation_ii/daq-components
- Whole chapter: https://www.bctengineer.com/md/semester_5/instrumentation_ii/chapter-5

## Question

What are the essential components of data acquisition system? Explain with the help of block diagram.

## Short answer

Essential components include sensors, signal conditioning, a multiplexer, sample-and-hold, ADC, and a computer with DAQ software. Additional elements are storage, display, and optional DAC outputs for control.

## Answer

A **data acquisition system (DAQ)** measures real-world physical quantities and converts them into digital data for a computer to process, display and store.

#### Block diagram
```text
 Physical   +--------+  +------------+  +-----+  +-----+
 quantity ->| Sensor |->| Signal     |->| MUX |->| S/H |->
 (temp,     |/Transd.|  | conditioner|  +-----+  +-----+
 pressure)  +--------+  +------------+
        +-----+     +-----------------+     +--------------------+
     -> | ADC |---> | Computer / uP   |---> | Display, storage,  |
        +-----+     | + DAQ software  |     | network, printer   |
                    +--------+--------+     +--------------------+
                             | DAC / digital out -> Actuator (control)
```
#### Essential components
1. **Sensors/transducers:** convert physical quantity to electrical signal (thermocouple, strain gauge, LDR).
2. **Signal conditioning:** amplification, filtering (anti-aliasing), isolation, linearisation, excitation, cold-junction compensation, level shifting.
3. **Multiplexer:** selects one of several channels for one ADC.
4. **Sample and hold:** keeps the input stable during conversion.
5. **ADC:** converts the analog signal into digital form (resolution, speed chosen from signal bandwidth).
6. **Computer / microprocessor / DAQ card:** timing and control, processing, and the bus interface (USB, PCI).
7. **Software:** drivers, acquisition, analysis, display (LabVIEW, MATLAB).
8. **Storage and display units,** and optional **DAC/actuator** outputs for control.
9. **Power supply and clock/timing.**

## Check yourself

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

1. Which functions does the signal conditioner perform in a DAQ?
   A. Storing data on disk
   B. Converting digital data to analog
   C. Selecting one of several channels
   D. Amplification, filtering, isolation, linearisation and excitation
   Answer: D. The conditioner prepares the sensor signal for the ADC. (Key point: Signal conditioning)

2. Why is a multiplexer used in a multi-channel DAQ?
   A. So one ADC can be shared by selecting one channel at a time
   B. To amplify each channel separately
   C. To keep the input steady during conversion
   D. To store the samples
   Answer: A. The MUX selects one of several inputs for the single ADC. (Key point: Multiplexer)

3. What is the role of the sample-and-hold circuit?
   A. To choose the channel
   B. To keep the input stable during the ADC conversion
   C. To filter out aliasing
   D. To convert digital back to analog
   Answer: B. S/H freezes the input while the ADC converts it. (Key point: Sample and hold)

4. Which conditioning step prevents aliasing before sampling?
   A. Cold-junction compensation
   B. Level shifting
   C. Low-pass anti-aliasing filter
   D. Linearisation
   Answer: C. The anti-aliasing filter removes frequencies above half the sampling rate. (Key point: Anti-aliasing)

## Related in Instrumentation II

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## Related in other subjects

- [Digital data acquisition system block diagram](https://www.bctengineer.com/question.md?key=semester_4%2Finstrumentation_i%3Adigital-data-acquisition-system) — Instrumentation I, chapter 6
- [Data acquisition block diagram and DCS advantages](https://www.bctengineer.com/question.md?key=semester_6%2Fdigital_control_system%3Adata-acquisition-advantages) — Digital Control System, chapter 1
- [Essential components of an activity diagram](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Aactivity-diagram-components) — Object Oriented Analysis and Design, chapter 2
- [Data acquisition, conversion and distribution](https://www.bctengineer.com/question.md?key=semester_6%2Fdigital_control_system%3Adata-acquisition-conversion-distribution) — Digital Control System, chapter 1, asked 9×