Reading the latest newsletter [link to follow!] ... sparked a thought!
Well it was in fact the article by Steve Smith of Pico, part 3 of his Scope School, so blame him!
Especially important for those of us struggling to "get more using less" ... of the limited number of physical cabled channels ... currently 4!
So take the AC DC coupling, and a single lead attached to the alternator positive ... is the "AC/DC coupling" feature a hardware element in the scope or software one? Would it be possible to provide both sets of Data for the user to display at the same time/use in Maths channels? ie
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For instance, we currently need to do 2 separate tests for the alternator, but with this simple (OK, might not be so simple ) change we could capture everything in one go. The second test does not move the leads, merely switches the use of 1 channel to AC.
For our test we use:
ChA - battery positive and our common ground
ChB - Amp clamp typically in 200amp mode, often At the battery for ease of access on the negative cable, but ideally at the alternator.
ChC - the alternator positive post (or as close to it as possible) so the nut, cable tag being 2nd best, or a junction box in the engine bay if the alternator is buried so deep in the V or under the exhaust manifold that it's impossible to access. Remember the further away you are the more detail will be 'damped' and by the time you get to the battery, you might have lost anything of value (we have lots of cars where alternator and battery are at opposite ends of the car)
ChD - alternator unit body (IE ground)
The DC coupled version of ChC gives us:
- alternator output in amps, we also load the alternator with a carbon pile tester to 50amp connected to the battery, or using some Nichrome wire tested for the purpose/rating desired). Often an alternator will give 8-15 amps but fail completely at 30-50amps, so this is key to checking the health of alternator, but also the volt drops below.
- positive volt drop - using a maths channel to calc (C-A) the drop between alternator and battery, especially at 50amps+ output.
- negative volt drop - ditto - but no maths needed
- voltage output, as we use a trigger we can see battery voltage before starting, and alternator output on a single screen.
The second test merely flips ChC to AC and repeats including loading, but rather than maths we look at the AC ripple, again using load to see if the diodes perform when loaded as well as at idle output.
Access to OBD engine revs would be great, as we also take revs to 2500-3000 rpm during this, and right now can't see this (OK, we could calc from the AC ripple, if we could trust it!)
I'll post a sample of the two tests on the same car, but but allowing access to both the AC and DC elements to be used separately from the same capture would allow all this from just one test.
I hope that makes sense and shows a genuine business case for the feature request! No we're not lazy, despite my remote keyboard , it gives more focus to analyse 1 capture and see different element correlate better.