Need Help with Open Collector Output

[Grumpy_Mike]

I tried to follow Mark T's advice but was a bit concerned about getting the 9V too close to the board. So instead I broke out the multimeter and started testing continuity and voltage. It appears that while the meter is still the resting voltage is 0.6V when the meter begins to spin, the voltage drops. The faster it spins the closer to 0 it gets. I don't know if that is a helpful observation or not.

If that is truly what you did and you included a pull up resistor to 9V then your meter is broken.
However given your track record to date it is hard to tell so how about some photographs of the meter with the wiring you tested.

[kevin567890]

I did not use a pull up resistor to the 9V. That was my concern also. Was the info I was able to gain from the multimeter helpful in understanding the OCO at all?

[Grumpy_Mike]

I did not use a pull up resistor to the 9V.

If you do not use a pull up resistor you will measure nothing from an open collector output.

[TomGeorge]

Hi, question, are you doing all this testing on a protoboard like in your fritzing?
If so, check that the positive and negative supply lines that run down the side of the protoboard are continuous for the entire length.
There are some out there that have a break in continuity half way down, in your case it would mean that the Black and battery negative are connected together but not connected to the arduino ground.

Tom......