What is the purpose of the sample-and-hold (S/H) block?

To keep the signal constant during ADC conversion

To select one channel at a time

The signal conditioner in a data logger:

Amplifies, filters and scales each signal to the ADC range

What does the microcontroller do in a data logger?

Controls the sequence, adds a time stamp and sends data to memory

Only converts analog to digital

2073 Bhadra · 4 marks

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.

Draw and explain the block diagram of data logger.

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

Block diagram

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

Explanation of blocks

Sensors/transducers: convert physical quantities to electrical signals.
Signal conditioner: amplifies, filters and scales each signal to the ADC range.
Multiplexer (MUX): connects the channels one at a time to a single ADC, so that one converter serves many sensors.
Sample and hold (S/H): holds the signal constant during conversion.
ADC: converts the analog value into a digital word.
Microcontroller: controls the sequence (including channel selection), adds a time stamp from the real-time clock, processes the data, and sends it to memory.
Memory: stores the logged data (SD card/flash/EEPROM).
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.

✓ Answer checked by Claude Opus 5.5 (high effort)

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