Using Tach/Dwell Meter - need some help

[rgnprof]

I have bought 2 different types of tachs lately to try and measure my '72 250 rpms. I bought a digital one that didn't work and then I bought an older Sears Engine Analyzer - analog with the needle, measures volts, amps, dwell, and low/hi rpms.

Trouble is I can't get either of them to measure my rpms. I have an Equus Tach/Dwell Meter that works but it only measures up to 1600 rpms. It has a green clip which connects to the -coil terminal and a black ground clip that goes on the -battery terminal.

I tried connecting the digital one the same way and the numbers just jump all over the place and the Sears one doesn't measure anything. The Sears model has red and black (battery?) clamps and a green clip and a plate. I tried attaching the green clip to the -coil terminal and the black to ground and nothing (BTW, the Sears analyzer came with no manual).

One bit of information - I am using a Crane optical ignition, but the Equus model seems to work fine - it just just doesn't read high rpms.

Anyone have any suggestions?

ryan