Analog-to-digital converters and digital-to-analog converters workshop

Abstract

A digital multimeter is a convenient tool to measure currents or voltages. It gives us better accuracy by displaying decimal values rather than the parallax error-prone needles of analog meters. But how do digital meters process analog input?
Analog-to-digital converters (ADCs) and digital-to-analog converters (DACs), as their names suggest, allow us to convert signals from one form to another. The difference between these two signals is similar to the difference between a ramp and a stairway. Moving along a ramp you can be at any height above ground; going upstairs you can be at only certain fixed heights above ground, depending on the step size (the resolution). The fact the digital values can only be in finite discrete levels means that it only approximates the analog value, and therefore, errors are introduced which can be minimized by increasing the resolution. Computers assume the information they process is in binary form. Thus, the binary system is used in digital processing, unlike in analog where we usually express them as decimal.
Various approaches can be used to implement an ADC. The simplest way is to have a voltage reference that is gradually incremented by a counter until its value is the closest approximation of the analog signal. A more elegant way is to use successive approximation, a technique that greatly reduces the number of trials to reach the desired value. DAC on the other hand reverses the process of ADC. It implements a ladder network of resistors, an ingenious application of Kirchhoff's current divider law. It can be seen that a DAC is also part of a complete ADC.
This workshop aims to explore the characteristics of these converters, how they work and why they work as such. As much as ten modules can be provided to interested participants. Hopefully, the activity will provide the participants insights as to how the digital tools process analog information.