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Wiring Fundamentals: Oscilloscope

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Oscilloscope

02.03

00:00 - Oscilloscopes can initially seem quite intimidating.
00:02 They provide an awful lot of data and it can be overwhelming to try and makes sense of it all.
00:07 Al they are though is a digital voltmeter that can show you how the voltage they're measuring has changed over time.
00:13 You can configure the voltage scale they display to make small changes much easier to see and change the time scale they take their measurements over to focus in on events that happen very quickly.
00:23 They're a tool that doesn't get pulled out of the toolbox with any particular regularity but when you do need one, there isn't another tool that will do the job.
00:30 Oscilloscopes used to be pretty unobtainable for the average person interested in modifying their car, or even for small workshops, as they were prohibitively expensive.
00:38 However in recent years, companies like Pico Technology have released PC based oscilloscopes that are catered towards the automotive aftermarket and are very reasonable priced.
00:47 However it is possible that you actually already have one installed in your vehicle.
00:52 Many aftermarket ECUs now include oscilloscope functionality which allow you to look at sensor signals, supply voltages and ground levels that the ECU is seeing in real time.
01:02 To show you how useful an oscilloscope can be and give you a little bit of familiarity with their use, we'll perform a common task undertaken when building an EFI wiring harness, that of confirming the polarity of the reluctor timing sensor fitted to the engine.
01:15 As we talked about in the sensor section of the course, correct reluctor sensor wire polarity is essential for stable ignition timing.
01:23 Much like our multimeter has a positive and negative probe, so does our oscilloscope.
01:28 Here we have the positive probe lead connected to the positive trigger input going to the ECU.
01:33 And the negative probe lead connected to the sensor ground.
01:36 As the engine is running, we can see the sensor signal coming out of the reluctor sensor rises from zero then sharply shoots down through zero to a negative reading, before returning to zero once again.
01:48 This zero crossing point is what the ECU is looking for.
01:51 And it's essential that it's in the negative direction.