Oxygen sensor tester

On the first two days of fuels, we constructed a device to test an oxygen sensor.
The tester consists of a small circuit board with numerous components including resistors, diodes and LEDs.

When we test the oxygen senser, weh connect the tester to the battery, and to the signal output of the sensor. We can then monitor what signals the oxygen sensor is putting out to the ECU. We can see this by the LEDs flashing. On my tester, the red LED meant it was running rich in fuel, and the green LED meant the engine was running lean of fuel.

We then proceeded to test the testers on an engine down stairs. We used my tester in conjunction with a digital read out tester aswell. I know my tester worked correctly because when the digital tester read rich, the red LED flashed on my tester, and the same with when the digital tester read lean, the green LED on my tester flashed simultaneously.