I have measured that signal from the rear end. It is a very slow AC sine wave signal that obviously increases with speed. Could not tell you PPM. At 5 mph maybe a pulse or 2 per second but cannot remember exactly. The important thing is that you should see the pulses. Best to use an analog meter and watch the needle jump. Seem to remember that I used the DC scale because the pulses were so slow, made the needle deflect positive and then towards the neg side beyond zero and against the pin then back again. Starts out about low at 2 or volts or so then that voltage increases to 5 or 6 volts with speed but that is incidental, the speedo is looking at the AC pulses not the voltage. I did this with one back wheel up off ground and turning it by hand (in nuetral of course). Also drove the car with entire instrument cluster out and my meter hooked up to the cable from sending unit sitting on the seat beside me. Believe it or not the car will run with the cluster removed.

My problem turned out to be a flakey connection inside the speedo.

I think the sender rarely gives problems

What are your symptoms?