Hello i got a Autometer A/F ratio gauge but i don't have the instructions... the model number is 4775 does anyone know of how to install it? there are 3 wires. i'm installing on a 95 H22A I know red to the lights, black to ground and purple to what wire off the sensor?

 

red - to some kind of power when the car is on
black - ground
violet/purple - white wire on o2 sensor