---
title: "Block diagram of data logger"
subject: "Basic Electronics Engineering"
chapter: 7
key: "semester_2/basic_electronics_engineering:data-logger-block-diagram"
source: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/data-logger-block-diagram
site: BCT Engineering
---

# Block diagram of data logger

Basic Electronics Engineering · Chapter 7: Application of Electronic System

- Asked in: 2073 Bhadra, 4 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/basic_electronics_engineering/data-logger-block-diagram
- Whole chapter: https://www.bctengineer.com/md/semester_2/basic_electronics_engineering/chapter-7

## Question

Draw and explain the block diagram of data logger.

## Short answer

A data logger automatically samples multiple sensor channels at intervals, digitizes via a multiplexer, sample/hold, ADC, and stores timestamped data. It comprises sensors, signal conditioner, MUX, S/H, ADC, microcontroller, memory, and display/PC interface.

## Answer

A **data logger** automatically measures several physical quantities at fixed intervals, converts them into digital form and stores them with time information.

#### Block diagram

```text
 +---------+  +------------+  +-----+  +-----+  +-----+
 | Sensors |->| Signal     |->| MUX |->| S/H |->| ADC |
 | (T,P,V) |  | conditioner|  +-----+  +-----+  +--+--+
 +---------+  +------------+                      |
                                                  v
 +-----------+   +---------+   +-----------------------+
 | Display / |<--| Memory  |<--|    Microcontroller    |
 | PC        |   | (flash) |   +-----------+-----------+
 +-----------+   +---------+               ^
                                           |
                                   +-------+-------+
                                   | Real-time     |
                                   | clock         |
                                   +---------------+
```

#### Explanation of blocks

1. **Sensors/transducers:** convert physical quantities to electrical signals.
2. **Signal conditioner:** amplifies, filters and scales each signal to the ADC range.
3. **Multiplexer (MUX):** connects the channels one at a time to a single ADC, so that one converter serves many sensors.
4. **Sample and hold (S/H):** holds the signal constant during conversion.
5. **ADC:** converts the analog value into a digital word.
6. **Microcontroller:** controls the sequence (including channel selection), adds a time stamp from the real-time clock, processes the data, and sends it to memory.
7. **Memory:** stores the logged data (SD card/flash/EEPROM).
8. **Display / PC interface:** shows the data, or transfers it through USB/serial for analysis.

A battery or mains supply powers the unit, so it can run unattended.

## Check yourself

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

1. What is the purpose of the sample-and-hold (S/H) block?
   A. To select one channel at a time
   B. To keep the signal constant during ADC conversion
   C. To store data permanently
   D. To amplify the signal
   Answer: B. The S/H holds the signal value steady while the ADC converts it. (Key point: Sample and hold)

2. The signal conditioner in a data logger:
   A. Adds the time stamp
   B. Controls the display
   C. Amplifies, filters and scales each signal to the ADC range
   D. Stores data in flash
   Answer: C. Sensor signals are made suitable for the ADC by amplification, filtering and scaling. (Key point: Signal conditioner)

3. What does the microcontroller do in a data logger?
   A. Controls the sequence, adds a time stamp and sends data to memory
   B. Only displays the data
   C. Only converts analog to digital
   D. Only senses the quantity
   Answer: A. It controls operation, time-stamps the data using the real-time clock, processes it and stores it in memory. (Key point: Microcontroller role)

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