13 Jul 2026

Study of Analogue-to-Digital and Digital-to-Analogue Converters

practical pg-ii adc dac digital-electronics

Aim

To study an analogue-to-digital converter and a digital-to-analogue converter and determine the step size and conversion error.

Apparatus

ADC/DAC trainer, regulated supply, function generator, CRO, digital multimeter, and patch cords.

Experimental arrangement

ADC and DAC converter trainer connection — The analogue input is converted to a binary code and then reconstructed by the DAC for comparison on the meter or CRO.

Theory

An ADC assigns a binary number to each allowed range of input voltage. For an $n$-bit converter with reference voltage $V_{ref}$, the ideal step size is

\[q=\frac{V_{ref}}{2^n}.\]

A DAC converts the binary code back into an analogue voltage. Quantisation means that the reconstructed output can differ from the input by approximately half to one least-significant-bit, depending on the conversion convention.

Observations

For an 8-bit, $5$ V converter, $q=19.53$ mV.

Input voltage (V)	ADC code	DAC output (V)	Error (mV)
0.50	00011010	0.508	8
1.00	00110011	0.996	4
2.50	10000000	2.510	10
4.00	11001101	4.000	0

Result

The ADC gives a monotonic binary code and the DAC reconstructs the input voltage with an error of about one least-significant bit or less.

Viva Questions

What is resolution? The analogue voltage represented by one digital count.
What is quantisation error? The difference between the input voltage and the nearest available digital level.
What is monotonicity? The output does not decrease when the input code increases.

Maxima Code

Download the PG-II electronics calculation file.

Aim