Focus piece: Current clamps and Fuse extensions
by Pico Technology

With today’s complex vehicle systems and accessibility to components seemingly more restrictive, using the fuse box to access these circuits can be an easy option (once you locate the correct fuse for the circuit you want to test). Refer to technical data for location of your vehicle's fuse boxes (usually one is found within the engine bay, and one can usually be found in one or other of the front footwell areas. Newer vehicles are also known to have a fusebox located in the luggage area.).

Once you have located the fuse of the component required for testing, remove the fuse and place it into the correct style fuse extension, then plug the fuse extension into the fuse's original location. Zero the Pico 20/60 A current clamp, and clamp around the fuse extension. 

You can use one of the 150 preset guided tests if one exists for the component you are testing. Alternatively you may also wish to manually setup the PicoScope software. Ensure that the 20/60 current clamp probe is chosen within the channel options, and a suitable timescale is selected. 

Start the vehicle, and analyze the results on screen. For many tests we do have preset Guided Tests available, which include both testing information and example waveforms. Below is an example of a fuel pump waveform:

Always remember to refer to vehicle manufacturer's data for specific values when comparing your results. With any waveform capture you can use the Notes feature of the PicoScope software (found under Edit > Notes) to record the fuse type and location both within fusebox and of the fusebox itself. Utilising our rulers tool, or automatic measurements you can clearly see your maximum current draw.

Good and bad waveforms are always good for learning and comparison. The waveform library may also have some saved waveforms for future reference of the model and vehicle you are working on.

We also cover this subject within a Case Study, based on an Audi A8 Injector fault.

There is also a YouTube video based on a fuel pump test for an Audi TT:


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