Make an electronics test lab

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The maker community is bringing electrical engineering back into vogue, but having the test gear can run into big money.

Before you unload your wallet, your old phone or tablet can help you learn the basics – and maybe even save you money.

What you’ll need:

Android

  • Android tablet or smartphone with Android 3.1/Honeycomb or later and 800×480-pixel resolution minimum
  • Waveform Generator app from Google Play
  • Spectrum Analyzer app from Google Play
  • Total cost: $2

iOS

  • iOS device with iOS 4.3 or newer
  • Signal Generator from Apple App Store
  • Total cost: $2
  • Total time to complete: 10 minutes

How it works

When building your own tech gear, having the right test equipment is like have the right debugging tools for coding your own apps – it can show what’s going wrong and help point you in the right direction.

A digital multimeter (DMM) is a must-have for any hobby electronics work, but three other pieces of test gear are well worth learning – the waveform generator, oscilloscope and spectrum analyser.

Using your device’s audio module, Android and iOS apps can turn your phone or tablet into a compact test lab.

Waveform Generator

waveEvery sound we hear is a complex mathematical combination of sinewaves, pure tones of a single pitch or ‘frequency’.

The Waveform Generator app on Android turns out 16-bit precision sinewaves from 1Hz to 22050Hz, dialed up with the app’s rotary control wheel and tap-selected display digits.

It also produces various colours of noise (brown, pink and white) plus advanced waveforms including amplitude and frequency modulation (AM/FM) and frequency sweeps.

siggenOn iOS, Signal Generator does similarly, producing sine and cosine sinewaves, along with sawtooth, square and triangle waveforms.

A 1kHz sinewave is a defacto standard test signal for most audio work – having a good-quality ‘sig-gen’ on your phone is pretty cool.

Spectrum Analyser

crospecA spectrum analyser enables you to see that complex mathematical combination of sinewave tones as a column graph of frequencies.

In industry, spectrum analysers often handle frequencies up to tens of GHz and cost thousands of dollars.

The Spectrum Analyzer app on Android allows you to view the whole audio spectrum (20Hz to 20kHz) on a tablet or phone, combining it with an oscilloscope view.

It only uses the microphone input to capture real-time audio, so don’t expect absolute accuracy, but it’ll give you invaluable experience and understanding on how spectrum analysers work.

Digital oscilloscope

keyWhile a spectrum analyser displays sound in terms of frequency, an oscilloscope displays signals over time.

The Spectrum Analyzer app on Android does both, showing the audio input in both time and frequency domains.

But things can get a whole lot more serious. Keysight (a double spin-off from Hewlett-Packard) makes digital storage oscilloscopes (DSOs) you can control from your iPad or Android device over Wi-Fi via your Windows PC.

For something more mobile, Oscium creates DSO modules for iOS – for US$300, the iMSO-104 turns an iOS 5.0 or newer device with a 30-pin connector into a 5MHz DSO with one analog and four digital inputs. The US$400 iMSO-204 adds a second analog input and is available for both 30-pin and Lightning connector devices.

Test equipment is fast making use of PC technology, so it’s inevitable we’ll see this gear take advantage of mobile tech. If you’re new learning physics or electronics at school or university, your phone is no longer just a phone.

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