I use one rarely.
I've got an ancient B+K Analog unit, and one of these little dinky cheap things:
https://www.amazon.com/gp/product/B079CPDVRG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I don't need it for much, but the few times I'm troubleshooting a pwm signal like tach, fuel injector pulse, and things of that nature it has been super helpful and at the price point its hard to go wrong, because if I blow it up, its not a huge loss.

The big downside is it does not have any kind of battery, so I taped a 9v batter with a little adapter to the back so I can run it without needing a power source.

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1982 300D (w123, "Grey Car")
1982 300D (w123, "Blue Car")
2001 Ford F150 "Clifford" (The Big Red Truck)
1997 Dodge Ram 2500 12V Cummins
1996 Dodge Ram 2500 12V Cummins
Previous Vehicles:
1995 E300D, 1980 300SD, 1992 Buick Century, 2005 Saturn Ion