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The voltage goes low as the driver switches on and pulls the injector to earth. You can use Channel A for current and channel B for voltage.

The voltage waveform is very different to the current waveform and usually, they are displayed simultaneously. Please Note: the voltage and current waveforms shown above are from different tests so the absolute time values do not correlate. Once the correct quantity of fuel is injected, the driver switches off and the current ceases flowing.Īlthough the current waveform shows when the injector opened, there is no information about when it closed which is why it is useful to see the voltage waveform at the same time. The current flattens out due to one or both of these factors. If the injector was purely inductive, the current would keep on rising however, the coil windings have resistance and sometimes the ECU drivers have current limiting. This is very obvious in this waveform but often it is just a slight bump or change in the slope. Notice the bump at about -1 ms which is caused by the change in inductance as the pintel (plunger) moved (opens). The current in the injector does not increase instantly but starts to rise slowly because the injector is inductive (coil). You can create a reference waveform to quickly compare multiple injectors on the screen. This can confirm the fuelling strategy under all test conditions. Read: Under certain engine conditions you may find that each injection event is visible and includes: pilot, pre-, main and post injection. Click the Go button or press the space bar to capture the waveform. Run: The engine must be running to perform this test. As injectors can produce back EMF voltage spikes, we advise using a PICO-TA197 Attenuator or the new PICO-TA499 10:1 Scope Probe and Adaptor to protect the oscilloscope inputs. You can also monitor the injector voltage by connecting directly to the injector using another channel. It may be necessary to pull back some of the loom’s outer shielding to fit the current clamp. Purpose of Test - Suspected Compression IssuesĬonnect: To test Injector Current, connect a PICO-TA018 20 A / 60 A Current Clamp or the new PICO-TA473 PicoBNC+ Current Clamp to Channel A on your PicoScope and place the clamp around the fuel injector supply wire.Software: PicoScope 6 - Guided Test AT004.All that is required is a current clamp and a test lead with a backpinning probe. An injector's current and / or voltage can be tested very easily.