2026 question paper

Signal Conditioning and Data Acquisition System

28 questions

1. Q1(a). A signal conditioner may be used to: (i) Generate source code (ii) Replace a transducer (iii) Filter unwanted components (iv) Store files20262m

   Module 2: Signal Conditioning Systems

   A signal conditioner may be used to:

   (i) Generate source code
   (ii) Replace a transducer
   (iii) Filter unwanted components
   (iv) Store files

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   Worked Solution

   Answer: (iii) Filter unwanted components

   A signal conditioner prepares a sensor signal for the ADC by amplifying, filtering, isolating and linearizing it. It does not replace the transducer or store files.

2. Q1(b). A DAC performs: (i) Voltage-to-frequency conversion (ii) Digital-to-analog conversion (iii) Current-to-resistance conversion (iv) Analog-to-digital conversion20262m

   Module 1: Introduction

   A DAC performs:

   (i) Voltage-to-frequency conversion
   (ii) Digital-to-analog conversion
   (iii) Current-to-resistance conversion
   (iv) Analog-to-digital conversion

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   Worked Solution

   Answer: (ii) Digital-to-analog conversion

   DAC = Digital-to-Analog Converter. It converts a digital code from a microcontroller into a proportional analog voltage or current. (ADC does the reverse.)

3. Q1(c). Which ADC uses successive approximation? (i) Dual-slope ADC (ii) Integrating ADC (iii) Flash ADC (iv) SAR ADC20262m

   Module 1: Introduction

   Which ADC uses successive approximation?

   (i) Dual-slope ADC
   (ii) Integrating ADC
   (iii) Flash ADC
   (iv) SAR ADC

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   Worked Solution

   Answer: (iv) SAR ADC

   SAR = Successive Approximation Register. It tests one bit at a time from MSB to LSB using a comparator and internal DAC, so an n-bit result needs n clock cycles.

4. Q1(d). Aliasing occurs when a signal is sampled: (i) After amplification (ii) At twice its frequency (iii) Below the required sampling rate (iv) With a low-pass filter20262m

   Module 2: Signal Conditioning Systems

   Aliasing occurs when a signal is sampled:

   (i) After amplification
   (ii) At twice its frequency
   (iii) Below the required sampling rate
   (iv) With a low-pass filter

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   Worked Solution

   Answer: (iii) Below the required sampling rate

   If sampling frequency is less than twice the highest signal frequency (Nyquist), high-frequency components appear as false lower frequencies. This is aliasing.

5. Q1(e). The Nyquist rate should be at least: (i) Equal to the signal frequency (ii) Half the signal frequency (iii) Four times the sampling period (iv) Twice the highest signal frequency20262m

   Module 2: Signal Conditioning Systems

   The Nyquist rate should be at least:

   (i) Equal to the signal frequency
   (ii) Half the signal frequency
   (iii) Four times the sampling period
   (iv) Twice the highest signal frequency

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   Worked Solution

   Answer: (iv) Twice the highest signal frequency

   Nyquist criterion: $f_s \ge 2 f_{max}$. Sampling at or above this rate allows the signal to be reconstructed without aliasing.

6. Q1(f). Which interface generally uses two signal lines, SDA and SCL? (i) UART (ii) USB (iii) I2C (iv) SPI20262m

   Module 3: Embedded Microcontrollers – PIC18F / Others

   Which interface generally uses two signal lines, SDA and SCL?

   (i) UART
   (ii) USB
   (iii) I2C
   (iv) SPI

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   Worked Solution

   Answer: (iii) I2C

   I2C uses only two lines: SDA (serial data) and SCL (serial clock), with addressing for multiple devices. SPI needs 4 lines and UART uses TX/RX.

7. Q1(g). In SPI, the line used to select a slave is: (i) SDA (ii) TX (iii) Chip Select (iv) SCL20262m

   Module 3: Embedded Microcontrollers – PIC18F / Others

   In SPI, the line used to select a slave is:

   (i) SDA
   (ii) TX
   (iii) Chip Select
   (iv) SCL

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   Worked Solution

   Answer: (iii) Chip Select

   SPI has MOSI, MISO, SCK and a Chip Select (CS/SS) line per slave. Pulling CS low selects that slave. SDA and SCL belong to I2C.

8. Q1(h). RS-485 is preferred when: (i) Analog filtering is required (ii) Only one sensor is used on a PCB (iii) Wireless communication is required (iv) Long-distance and multi-point communication is required20262m

   Module 4: DAQ Systems

   RS-485 is preferred when:

   (i) Analog filtering is required
   (ii) Only one sensor is used on a PCB
   (iii) Wireless communication is required
   (iv) Long-distance and multi-point communication is required

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   Worked Solution

   Answer: (iv) Long-distance and multi-point communication is required

   RS-485 uses differential signalling, so it works up to about 1200 m with good noise immunity and supports up to 32 or more nodes on one bus.

9. Q1(i). Which is a common data-storage device for embedded systems? (i) SD card (ii) DAC (iii) Operational amplifier (iv) ADC20262m

   Module 5: Data Processing

   Which is a common data-storage device for embedded systems?

   (i) SD card
   (ii) DAC
   (iii) Operational amplifier
   (iv) ADC

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   Worked Solution

   Answer: (i) SD card

   SD cards are non-volatile, cheap, high-capacity storage connected over SPI or SDIO. DAC, op-amp and ADC are signal-conversion or conditioning devices, not storage.

10. Q1(j). Data logging mainly involves: (i) Changing sensor type (ii) Generating sensor output (iii) Amplifying every signal (iv) Recording acquired data20262m

    Module 5: Data Processing

    Data logging mainly involves:

    (i) Changing sensor type
    (ii) Generating sensor output
    (iii) Amplifying every signal
    (iv) Recording acquired data

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    Worked Solution

    Answer: (iv) Recording acquired data

    Data logging means acquiring measurements and storing them (usually with timestamps) in memory, SD card or a computer for later analysis.

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12. Q2(a). Describe the block diagram and working of a basic data acquisition system. Explain single-channel and multichannel DAQ systems.20267m

    Module 1: Introduction

    Describe the block diagram and working of a basic data acquisition system. Explain single-channel and multichannel DAQ systems.

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    Worked Solution

    Data Acquisition System (DAS)

    A DAQ system collects physical signals (temperature, pressure, strain, biopotential), converts them to digital form and sends them to a computer or microcontroller for display, storage and analysis.

    Block diagram

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    Working

    Block	Function
    Sensor / transducer	Converts the physical quantity into an electrical signal
    Signal conditioning	Amplifies, filters, isolates and linearizes the signal
    Sample and hold	Freezes the input while the ADC converts
    ADC	Converts the analog value to a digital code
    Processor / PC	Processes, scales and logs the data
    Display / storage	Shows results and saves them

    Single-channel DAQ

    One sensor feeds one conditioning circuit and one ADC. It is simple and cheap, and used when only one quantity is measured.

    Multichannel DAQ

    Many sensors are measured with one ADC by a multiplexer (MUX) that selects one channel at a time, or by one ADC per channel.

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    Point	Single-channel	Multichannel
    Sensors	One	Many
    Components	Few	MUX, extra control
    Cost	Low	Higher but shares ADC
    Sampling	Continuous	Sequential, per-channel rate is lower

    Exam tip

    Draw both block diagrams and mention that the multiplexer shares one ADC to save cost.

13. Q2(b). Discuss the working of ADCs and DACs with suitable block diagrams. Mention their applications in DAQ systems.20267m

    Module 1: Introduction

    Discuss the working of ADCs and DACs with suitable block diagrams. Mention their applications in DAQ systems.

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    Worked Solution

    ADC and DAC

    ADC (Analog-to-Digital Converter)

    Converts a continuous analog voltage into an n-bit digital code. Resolution: $\Delta = V_{ref}/2^n$.

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    SAR ADC working: a successive approximation register sets bits from MSB to LSB; an internal DAC output is compared with the input; the comparator keeps or clears each bit. Result is ready after n clock cycles.

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    ADC type	Speed	Resolution	Use
    Flash	Fastest	Low	Video, oscilloscopes
    SAR	Medium	8 to 18 bit	General DAQ
    Dual-slope	Slow	High	Digital multimeters
    Sigma-delta	Slow to medium	Very high	Biomedical, audio

    DAC (Digital-to-Analog Converter)

    Converts a digital code into an analog voltage: $V_{out} = V_{ref} \cdot D/2^n$.

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    The R-2R ladder is common because it needs only two resistor values and is accurate.

    Applications in DAQ

    • ADC: digitizes sensor signals such as ECG, temperature and pressure.
    • DAC: produces control signals, test stimulus, waveform generation, actuator drive and calibration.

    Exam tip

    Give the formula for resolution, draw the SAR block diagram and the R-2R DAC.

14. Q3(a). Discuss the need for signal conditioning. Describe amplification, attenuation, isolation and linearization.20267m

    Module 2: Signal Conditioning Systems

    Discuss the need for signal conditioning. Describe amplification, attenuation, isolation and linearization.

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    Worked Solution

    Need for Signal Conditioning

    Sensor outputs are usually small (mV), noisy, non-linear, or at levels the ADC cannot accept directly. Signal conditioning converts them into a clean signal that matches the ADC input range.

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    Needs

    1. Weak signals must be amplified.
    2. Noise and interference must be removed.
    3. Protection from high voltages and ground loops.
    4. Sensor non-linearity must be corrected.
    5. Match ADC input range and impedance.

    Amplification

    Increases signal level, e.g. thermocouple mV to 0-5 V. An instrumentation amplifier is preferred for bridges because of high input impedance and high CMRR. Gain: $G = 1 + 2R_f/R_g$ (3 op-amp in-amp).

    Attenuation

    Reduces large signals to the ADC range, using a resistor divider: $V_{out}= V_{in}\,R_2/(R_1+R_2)$.

    Isolation

    Electrically separates the sensor side from the DAQ side using optocouplers, transformers or isolation amplifiers. It prevents ground loops, protects the patient and equipment, and rejects common-mode voltage.

    Linearization

    Corrects a non-linear sensor response (thermistor, thermocouple) using analog circuits, look-up tables or polynomial equations in software, so output is proportional to the measured quantity.

    Function	Purpose
    Amplification	Raise small signals
    Attenuation	Bring large signals into range
    Isolation	Safety, no ground loops
    Linearization	Proportional output

    Exam tip

    Mention the in-amp for amplification, optocoupler for isolation and look-up table for linearization.

15. Q3(b). Compare plug-in boards, direct-connect modules, two-wire transmitters and distributed I/O arrangements.20267m

    Module 2: Signal Conditioning Systems

    Compare plug-in boards, direct-connect modules, two-wire transmitters and distributed I/O arrangements.

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    Worked Solution

    Signal Conditioning Arrangements

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    Feature	Plug-in boards	Direct-connect modules	Two-wire transmitters	Distributed I/O
    Location	Inside PC slot	External module wired to the DAQ	Mounted near sensor	Remote nodes on a network
    Output	Raw digital via PC bus	Conditioned analog or digital	4-20 mA current loop	Digital over RS-485 or Ethernet
    Distance	Short	Short to medium	Long (hundreds of metres)	Very long
    Noise immunity	Low (inside PC)	Medium	High (current signal)	High
    Channels	Limited by slots	Moderate	One per transmitter	Many nodes
    Cost	Low	Medium	Medium	High
    Use	Lab setups	Industrial measurement	Process control	Large plants

    Key points

    • Plug-in boards: ADC plus conditioning on a card in the computer; fast, but noisy PC environment.
    • Direct-connect modules: sensor connects to a conditioning module (e.g. SCXI-type) which then connects to the DAQ.
    • Two-wire transmitters: the same two wires carry power and the 4-20 mA signal; live zero (4 mA) allows wire-break detection.
    • Distributed I/O: remote units digitize locally and send data over a network, avoiding long analog runs.

    Exam tip

    A comparison table like the above gets full marks; mention 4-20 mA.

16. Q4(a). What are the common sources of noise in measurement systems? Suggest suitable methods for minimizing noise.20267m

    Module 2: Signal Conditioning Systems

    What are the common sources of noise in measurement systems? Suggest suitable methods for minimizing noise.

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    Worked Solution

    Noise in Measurement Systems

    Noise is any unwanted signal that corrupts the measured signal and reduces the signal-to-noise ratio, $SNR = 20\log(V_s/V_n)$ dB.

    Sources of noise

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    Source	Cause
    Thermal (Johnson)	Random motion of electrons in resistors, $V_n=\sqrt{4kTRB}$
    Shot	Discrete charge flow across junctions
    Flicker (1/f)	Low-frequency device imperfections
    Power line	50 Hz mains coupling (capacitive or inductive)
    EMI / RFI	Motors, relays, radio transmitters
    Ground loop	Different ground potentials
    Crosstalk	Coupling between adjacent wires

    Methods to minimize noise

    1. Shielding of cables and sensors, grounded at one point.
    2. Twisted-pair wiring so induced noise cancels.
    3. Differential measurement and an instrumentation amplifier with high CMRR.
    4. Filtering: low-pass, notch (50 Hz) and band-pass filters.
    5. Proper grounding (single point) and star ground to avoid loops.
    6. Isolation using optocouplers or isolation amplifiers.
    7. Averaging of repeated samples and lock-in techniques.
    8. Keep signal cables away from power lines; use short leads and low source resistance.

    Exam tip

    Classify as internal and external, give 3 sources and at least 5 remedies.

17. Q4(b). Explain sampling and aliasing. Discuss the role of anti-aliasing prefilters and compare first-order and second-order filters.20267m

    Module 2: Signal Conditioning Systems

    Explain sampling and aliasing. Discuss the role of anti-aliasing prefilters and compare first-order and second-order filters.

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    Worked Solution

    Sampling and Aliasing

    Sampling converts a continuous signal into discrete values taken every $T_s = 1/f_s$ seconds.

    Nyquist theorem: $f_s \ge 2 f_{max}$. If $f_s < 2f_{max}$, higher frequencies fold back as false lower frequencies. This is aliasing, and it cannot be removed after sampling. Alias frequency: $f_a = |f - n f_s|$.

    Example: a 700 Hz signal sampled at 1000 Hz appears as 300 Hz.

    SVGVector Architecture Diagram (SVG)

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    Anti-aliasing prefilter

    A low-pass filter placed before the ADC removes frequency components above $f_s/2$, so aliasing cannot occur. Cut-off is set at or slightly below $f_s/2$.

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    First-order vs second-order filter

    Point	First order	Second order
    Roll-off	20 dB per decade	40 dB per decade
    Components	One R and one C	Two R, two C (or op-amp stage)
    Cut-off sharpness	Gradual	Sharper
    Aliasing rejection	Poor, needs high $f_s$	Better
    Complexity	Simple	Moderate
    Use	Basic smoothing	Practical anti-aliasing

    Exam tip

    State Nyquist, give the alias formula and place the filter before the ADC in the diagram.

18. Q5(a). Describe the architecture of a PIC18F microcontroller and discuss the role of timers and counters.20267m

    Module 3: Embedded Microcontrollers – PIC18F / Others

    Describe the architecture of a PIC18F microcontroller and discuss the role of timers and counters.

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    Worked Solution

    PIC18F Architecture

    The PIC18F family is an 8-bit RISC microcontroller from Microchip with Harvard architecture (separate program and data buses), so instructions and data are fetched at the same time.

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    Main features

    Block	Description
    CPU	8-bit, 16-bit instruction width, about 75 instructions, hardware multiplier 8x8
    Program memory	Flash, 16 KB to 128 KB
    Data memory	SRAM up to 4 KB, banked, plus special function registers
    EEPROM	Non-volatile storage for settings
    I/O ports	PORTA to PORTE with TRIS direction registers
    Peripherals	10-bit ADC, comparators, CCP/PWM, UART, SPI, I2C
    Interrupts	Priority-based, high and low levels
    Clock	Internal or external oscillator with PLL

    Timers and counters

    A timer counts internal clock pulses ($f_{osc}/4$), so it measures time. A counter counts external pulses on a pin, so it counts events.

    Timer	Size	Typical use
    Timer0	8 or 16 bit	Delays, event counting
    Timer1	16 bit	Real-time clock, capture
    Timer2	8 bit	PWM time base
    Timer3	16 bit	Capture/compare

    Delay: $T = (65536 - preload) \times prescaler \times 4/f_{osc}$.

    Applications: periodic ADC sampling, PWM motor control, pulse width and frequency measurement, timeouts.

    Exam tip

    Draw the block diagram, name Harvard architecture and give the timer vs counter difference.

19. Q5(b). Describe ADC and DAC interfacing with a microcontroller. Compare SPI and I2C communication.20267m

    Module 3: Embedded Microcontrollers – PIC18F / Others

    Describe ADC and DAC interfacing with a microcontroller. Compare SPI and I2C communication.

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    Worked Solution

    ADC and DAC Interfacing with a Microcontroller

    ADC interfacing

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    • On-chip ADC (PIC18F): 10-bit, multiplexed analog pins. Steps: set pin as analog, select channel, set Vref and acquisition time, start conversion (GO/DONE), wait for completion, read ADRESH:ADRESL.
    • External ADC: (e.g. MCP3208 over SPI) used when higher resolution or more channels are needed.
    • Digital value: $D = (V_{in}/V_{ref}) \times (2^n - 1)$.

    DAC interfacing

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    • Parallel DAC (DAC0808) connected to a port, or serial DAC (MCP4921 on SPI, MCP4725 on I2C).
    • Microcontroller writes the code; output $V_{out} = V_{ref}\cdot D/2^n$; an op-amp buffers it.
    • Uses: waveform generation, motor speed, calibration.

    SPI vs I2C

    Point	SPI	I2C
    Lines	4 (MOSI, MISO, SCK, CS)	2 (SDA, SCL)
    Speed	Faster (10 MHz or more)	100 kHz, 400 kHz, 3.4 MHz
    Addressing	Chip select per slave	7-bit address in protocol
    Duplex	Full duplex	Half duplex
    Devices	Few (more CS lines)	Many on one bus
    Complexity	Simple hardware	Protocol overhead, ACK
    Use	ADC, SD card, display	EEPROM, RTC, sensors

    Exam tip

    Explain the ADC steps on PIC18F and finish with the SPI vs I2C table.

20. Q6(a). Discuss microcontroller-based DAQ systems and their basic hardware organization.20267m

    Module 4: DAQ Systems

    Discuss microcontroller-based DAQ systems and their basic hardware organization.

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    Worked Solution

    Microcontroller-based DAQ System

    A microcontroller-based DAQ uses a microcontroller as the central unit to acquire, process, store and transmit data. It is compact, low cost, low power and portable.

    Hardware organization

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    Block	Role
    Sensors	Convert physical quantity to electrical signal
    Signal conditioning	Amplify, filter, isolate
    Multiplexer	Selects among several channels
    ADC	Digitizes the signal
    Microcontroller	Controls sampling, processing, scaling, logging
    RTC	Adds timestamps
    Memory	Stores data (SD card, EEPROM, Flash)
    Display / keypad	Local user interface
    Communication	Sends data to PC (UART, USB, SPI, I2C, Bluetooth, Wi-Fi)
    Power	Battery or regulated supply

    Working

    1. Timer triggers sampling at fixed rate.
    2. MCU selects channel and starts ADC conversion.
    3. The result is scaled, filtered and time-stamped.
    4. Data is stored and/or sent to the PC.

    Advantages

    Low cost, portable, programmable, flexible and expandable. Limitations: limited speed and memory compared to PC-based DAQ.

    Exam tip

    Draw the block diagram with MCU at the centre and explain the 4 working steps.

21. Q6(b). Compare SPI, I2C, USB, USART and UART with respect to lines, speed and typical use.20267m

    Module 4: DAQ Systems

    Compare SPI, I2C, USB, USART and UART with respect to lines, speed and typical use.

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    Worked Solution

    Comparison of Serial Interfaces

    Feature	SPI	I2C	USB	USART	UART
    Full form	Serial Peripheral Interface	Inter-Integrated Circuit	Universal Serial Bus	Universal Synchronous/Asynchronous Receiver Transmitter	Universal Asynchronous Receiver Transmitter
    Lines	4 (MOSI, MISO, SCK, CS)	2 (SDA, SCL)	4 (VBUS, D+, D-, GND)	TX, RX (+ XCK clock in sync mode)	2 (TX, RX) + GND
    Clock	Synchronous	Synchronous	Embedded in data	Sync or async	Asynchronous (baud rate)
    Speed	Up to tens of Mbps	100 kbps, 400 kbps, 3.4 Mbps	12 Mbps (USB 1.1), 480 Mbps (USB 2.0) and higher	Up to a few Mbps	9600 to 115200 bps typical
    Topology	Master with many slaves	Multi-master, multi-slave	Host with hubs and devices	Point to point	Point to point
    Distance	Short (on PCB)	Short (on PCB)	Up to 5 m	Short to medium	Short (RS-232 up to 15 m)
    Typical use	ADC, SD card, display	EEPROM, RTC, sensors	PC connection, data loggers	Microcontroller to PC, modems	GPS, Bluetooth modules, debug console

    Key notes

    • SPI is fastest for chip-to-chip links but uses more pins.
    • I2C needs only two wires and supports addressing; pull-up resistors are required.
    • USB is plug-and-play with power supply and standard drivers.
    • UART needs no clock; both sides must use the same baud rate, format 8N1.
    • USART can work as UART or with a shared clock for synchronous mode.

    Exam tip

    A table covering lines, speed and use is exactly what the question asks.

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23. Q7(a). Differentiate between RS-232, RS-485, Ethernet and USB interfaces used for data loggers.20267m

    Module 4: DAQ Systems

    Differentiate between RS-232, RS-485, Ethernet and USB interfaces used for data loggers.

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    Worked Solution

    Data Logger Interfaces

    Feature	RS-232	RS-485	Ethernet	USB
    Signalling	Single-ended, +/-3 to 15 V	Differential	Differential twisted pair	Differential D+/D-
    Devices	1 to 1 (point to point)	Up to 32 or more nodes (multi-drop)	Many via switch	1 host to many via hub
    Max distance	About 15 m	About 1200 m	100 m per segment (copper)	About 5 m per cable
    Speed	Up to 115.2 kbps (typ.)	Up to 10 Mbps at short range	10/100/1000 Mbps	12 Mbps to several Gbps
    Noise immunity	Low	High	High	Medium
    Duplex	Full	Half (2 wire) or full (4 wire)	Full	Half or full
    Power supply	No	No	Optional (PoE)	Yes (5 V bus)
    Cost	Low	Low	Medium	Low
    Typical use	Old instruments, configuration	Industrial networks, Modbus RTU	Networked and remote logging	Direct PC connection, download

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    Selection guide

    • Long distance, many loggers, noisy plant: RS-485.
    • Remote monitoring over a network: Ethernet.
    • Quick local download: USB.
    • Simple one-to-one legacy link: RS-232.

    Exam tip

    Write the table and a one-line use case for each interface.

24. Q7(b). Outline the steps involved in transferring acquired data from the sensor to storage.20267m

    Module 5: Data Processing

    Outline the steps involved in transferring acquired data from the sensor to storage.

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    Worked Solution

    Data Transfer from Sensor to Storage

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    Steps

    1. Sensing: the transducer converts the physical quantity into an electrical signal.
    2. Signal conditioning: amplification, filtering, isolation and linearization.
    3. Anti-aliasing filtering: removes frequencies above $f_s/2$.
    4. Sample and hold: keeps the value constant during conversion.
    5. Analog-to-digital conversion: produces a digital code.
    6. Reading by the microcontroller: over the internal bus or SPI/I2C.
    7. Processing: scaling to engineering units, calibration, averaging, threshold checking.
    8. Time-stamping: RTC adds date and time to each sample.
    9. Storage: written to SD card, EEPROM or Flash in a file format such as CSV.
    10. Transfer: sent to a PC or cloud over UART, USB, Ethernet or wireless for analysis.

    Exam tip

    A numbered list of these steps with the flowchart is enough for 7 marks.

25. Q8(a). What are the different techniques used for measurement data processing? Discuss.20267m

    Module 5: Data Processing

    What are the different techniques used for measurement data processing? Discuss.

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    Worked Solution

    Measurement Data Processing Techniques

    Raw acquired data must be processed to remove errors and extract useful information.

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    Technique	Purpose
    Scaling and calibration	Convert ADC counts to engineering units, correct offset and gain
    Digital filtering	Low-pass, high-pass, notch, moving average, to remove noise
    Linearization	Look-up table or polynomial for non-linear sensors
    Averaging	Reduces random noise by $\sqrt{N}$
    Smoothing	Moving average, median filter
    Peak and threshold detection	Finds events such as the R wave in ECG
    Frequency analysis (FFT)	Finds frequency content of the signal
    Statistical analysis	Mean, standard deviation, variance, correlation
    Curve fitting / regression	Fits a mathematical model to the data
    Data compression	Reduces storage size

    Moving average

    $y[n] = \frac{1}{N}\sum_{k=0}^{N-1} x[n-k]$

    Exam tip

    List 6 techniques with a one-line purpose each and include the FFT and averaging.

26. Q8(b). Describe data retrieval and plotting. How can plots help in interpreting measurement data?20267m

    Module 6: Analysis

    Describe data retrieval and plotting. How can plots help in interpreting measurement data?

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    Worked Solution

    Data Retrieval and Plotting

    Data retrieval

    Retrieval means reading the stored data back for analysis.

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    • Data is saved as CSV, TXT or binary files, often with timestamps.
    • Tools: Excel, MATLAB, Python (pandas, matplotlib), LabVIEW, vendor software.
    • Cleaning: remove invalid samples, fill gaps, convert units.

    Plotting

    Plot	Use
    Line plot (value vs time)	Trends, drift, signal waveform
    Scatter plot	Relationship between two variables, calibration
    Histogram	Distribution of measurements
    Spectrum plot (FFT)	Frequency content, noise peaks
    Bar chart	Comparison of channels or groups
    Box plot	Spread and outliers

    How plots help interpretation

    1. Show trends, peaks, steps and drift quickly.
    2. Reveal outliers and sensor faults.
    3. Show noise and interference (e.g. 50 Hz in the spectrum).
    4. Allow comparison of channels, trials or conditions.
    5. Verify calibration through a fitted line and its slope.
    6. Communicate results clearly to others.

    Good plots have labelled axes with units, a title, a legend and a suitable scale.

    Exam tip

    Mention retrieval steps first, then 3 plot types and 4 benefits.

27. Q9(a). Write a short note on: Shielded and twisted-pair cables20267m

    Module 2: Signal Conditioning Systems

    Write a short note on: Shielded and twisted-pair cables

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    Worked Solution

    Short Note: Shielded and Twisted-Pair Cables

    Both reduce electromagnetic interference (EMI) picked up by signal cables.

    Twisted pair

    Two insulated wires twisted together. Interference induces equal voltages in both wires; a differential receiver cancels these (common-mode). Closer twists give better rejection, especially of magnetic fields.

    Shielded cable

    The conductors are surrounded by a metal foil or braid, grounded at one end (normally the signal source end), which blocks electric-field (capacitive) interference and prevents ground loops.

    MermaidDiagram

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    Point	Twisted pair	Shielded
    Protects against	Magnetic and common-mode noise	Electric-field noise, RFI
    Cost	Low	Higher
    Use	Ethernet, RS-485	Low-level sensor signals, audio

    Shielded twisted pair (STP) combines both and is used for thermocouples, ECG leads and RS-485.

    Exam tip

    Explain cancellation in twisted pair and single-point grounding of the shield.

28. Q9(b). Write a short note on: Anti-aliasing filter20267m

    Module 2: Signal Conditioning Systems

    Write a short note on: Anti-aliasing filter

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    Worked Solution

    Short Note: Anti-aliasing Filter

    An anti-aliasing filter is a low-pass filter placed before the ADC to remove signal components above half the sampling frequency ($f_s/2$), preventing aliasing.

    MermaidDiagram

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    • Cut-off frequency is set at or just below $f_s/2$.
    • RC filter (first order): $f_c = 1/(2\pi RC)$, 20 dB/decade roll-off.
    • Higher-order Butterworth or Bessel active filters give sharper roll-off. Oversampling with a simple filter is an alternative.
    • Aliasing cannot be corrected after sampling, so the filter is essential.

    Exam tip

    Draw the block diagram and give the RC cut-off formula.

29. Q9(c). Write a short note on: UART and USART20267m

    Module 4: DAQ Systems

    Write a short note on: UART and USART

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    Worked Solution

    Short Note: UART and USART

    UART

    Universal Asynchronous Receiver Transmitter: a serial link using two lines, TX and RX (plus GND), with no clock line. Both ends must use the same baud rate.

    Frame: 1 start bit (0), 5 to 9 data bits (LSB first), optional parity bit, 1 or 2 stop bits (1).

    MermaidDiagram

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    USART

    Universal Synchronous/Asynchronous Receiver Transmitter: works as a UART, or in synchronous mode with a shared clock (XCK) that allows higher speed and no start/stop bits.

    Point	UART	USART
    Clock	None, baud rate agreed	Optional shared clock
    Modes	Asynchronous only	Async and sync
    Speed	Moderate	Higher in sync mode
    Lines	TX, RX	TX, RX, XCK

    Used with RS-232/RS-485 drivers, GPS, Bluetooth modules and PC serial links.

    Exam tip

    Draw the frame format and the UART vs USART table.

30. Q9(d). Write a short note on: Data plotting and visualization20267m

    Module 6: Analysis

    Write a short note on: Data plotting and visualization

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    Worked Solution

    Short Note: Data Plotting and Visualization

    Plotting turns numerical measurement data into graphs so that patterns can be understood quickly.

    MermaidDiagram

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    Plot	Shows
    Time plot	Variation with time, trends
    Scatter plot	Relation between two variables
    Histogram	Distribution, noise level
    FFT spectrum	Frequency content
    Real-time strip chart	Live monitoring

    • Tools: Excel, MATLAB, Python (matplotlib), LabVIEW, Grafana dashboards.
    • Good practice: axis labels with units, legend, title, suitable scale and markers.
    • Benefits: easy detection of outliers, drift and noise; comparison of channels; clear presentation of results.

    Exam tip

    List 4 plot types, 2 tools and 3 benefits.