Virtual Instruments

Introduction

Measurement instruments like multi-meters, pulse generators or oscilloscopes can be rather costly and the requirements for the IoT course are rather modest with respect to signal height (we have either digital signals of 0 or 3.3V or analogue signals in the same range) or with respect to frequency (a few kHz max).

The ESP32 has a Digital to Analogue Converter (DAC), which can be uses to generate signals of any shape, and it has an ADC which can be used to sample analogue signals.

Three types of instruments have been implemented:

• a signal generator
• a voltmeter
• an oscilloscope

Each of the instruments consists of a TCP server running of the ESP. This server generates the analogue signal for the pulse generator using the 8-bit DAC provided by the ESP32 or samples the analogue signal to be measured using its ADC in case of the voltmeter and the oscilloscope.

An application with a Graphical User Interface (GUI), created with the Qt5 library implements a TCP client that connects to the server, gets the measured data from it and displays them in a user-friendly manner. Measurement parameters, like the pulse shape and frequency in case of the pulse generator can also be set using GUI elements.

A Virtual Voltmeter

The simplest of the virtual instruments is certainly the Voltmeter.

-- Uli Raich - 2021-05-15

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