I got this from a friend of my uncle. He makes them from scratch. It is pretty precise, since it has 30 LEDs in all. Has helped me solve two problems so far: O2 sensor, and an exhaust manifold leak.
The red light on the far left is the power light. it stays on. sensor hasnt warmed up enough to send a signal yet.
Green for Rich
Orange for middle
And red is for lean.

The red light on the far left is the power light. it stays on. sensor hasnt warmed up enough to send a signal yet.

Green for Rich

Orange for middle
And red is for lean.