It seems like this should be an easy way to make a crude Air/Fuel gauge for basic carburetor tuning on normally aspirated cars.

The signal really should be cleaned up by a signal conditioner of some sort, using a multimeter will bounce around to a point it will not be useful.

Wideband gauges that can log to a laptop are "cheap" and come with the proper bungs and sensors.

My LC-2 was $160 shipped.

You can with a narrow band sensor but it does not tell you much. Hook the heater up to 12V and measure the output of the sensor. With the engine running, the sensor will read 1 volt when at 14.7 to 1 AFR. Any other voltage indicates the AFR is not stoic. Wideband sensors give you a lot more information but they are not linear and indicators like the LC-1 translates the voltages for you into AFR. There are Arduino applications to do the same thing:
https://www.youtube.com/watch?v=W9Izy425jGQ
Craig

Widebands are actually linear. My LC2 talks to my Megasquirt ECU with a two-point line, "what AFR 0v" is and "what AFR 5v is".

Arduinos are fun to play with and I could see this being one of the lowest-cost solutions, if you have a little electrical/coding background.

I dont run an 02 sensor on my 63 as I have only worked with the factory setups. Sure I could read them with my fluke meter but it was easier to read it on the scanner through the PCM after it sends the signal to the scanner through the communication system the scanner uses with the PCM. Course on the factory setups of 0 to 1 volt the normal switching point is .5 volt which on that setup was over .5 is rich and the PCM will adjust pulsewidth to lean out and when it goes under .5 the PCM will add pulsewidth to richen some. I cant see that type being any help and some years even read from 2.5 to 3.5 as they biased 2.5 volts on the ground. But I have not worked with the aftermarket wide band systems. I have read the factory 02 sensors with my fluke but it switches so fast that the only way I would read them so I could use the info was on the recorder when I recorded the readings and played them back in slow motion on the shop computer. I thought the aftermarket 02 widebands were not to pricey ? Ron

Use an analog meter, response time is slow enough to "condition" the signal.

Wideband o2 sensors are fairly cheap these days. I have one with with an analog gauge in the dash. It's a great tuning aid. I thought that I would take it out after I had the carb dialed in but I like having it so much that I just left it.

I have used a simple volt meter with narrow band sensors... from memory about .5 volt is stoichiometric and .9 volt is getting rich... as much as a narrow band can measure.

I used it on an older stock FI type setup and modified engine to help get it checked out and dialed in.

I did it for a bit, the farther away from 14.7 the less accurate. Tuning not so good. Fuel starvation at higher rpm it works. Goes pig fat it works. Not for fine tuning.

Mine was even easier: just told the Megasquirt it was an LC-2 (LC-1 with no display).
Craig

The preloaded LC2 numbers varied slightly from how my LC2 came from Innovate, so I loaded those specific numbers in.