There is a way to set CO without an analyzer but I do not have my manual handy, so perhaps I can look that up tonight.
With an analyzer, on vehicles with a cat one must keep in mind that cats do not effect the amount of CO2 and O2 in the exhaust stream, therefore by measuring these gasses along with HC and CO we can see what an engine is doing. If your engines have an air pump or air injection system it must be disconnected or plugged before testing the exhaust.
The exhaust of a normal engine will be about 13.8 to 15% CO2 and 1-2% O2 if an engine is running rich the O2 will be lower than this and CO will be high, if lean, O2 will be higher and CO low. Since CO2 is a by product of combustion, the % CO2 is dependant on combustion efficiency including the air/fuel ratios. The % CO2 decreases as as the air/fuel mixture becomes rich or lean.
measuring the exhaust quantity of a vehicle with a cat does not accurately descibe the conditions of the engine. If the cat is working properly it will be reducing the amount of HC and CO in the exhaust stream before it exits the tailpipe So to use an analyzer one should test exhasut gasses that have not been treated. One way to do this is to insert the test probe into a hole drilled in front of the cat or, on some models techs are to insert the test probe into the exhasut opening of the ERG valve.
A properly tuned vehicle with computer controls will emit approximately 50ppm HC or less.Less than .5% CO, 1-2% O2 and 13.8-15% CO2.