Generally, yes, manually. By turning the big knob with one hand and watching the meter with the other.
Or perhaps watching it with your eyes. Just don't try to turn the knob with your eyes.
(I'm poking fun at me, not you. Yes I really wrote that you should watch the meter with your hand -- I should wake up before posting in the future)
The reading at Vo will never be zero unless the imaginary part of the impedance is zero (i.e. it is a pure resistance). It will, however be symmetrical about zero when the bridge is balanced (or as balanced as it can be with a resistance on one side and a reactance on the other.
Sorry, I actually said an AC voltmeter. That was a mistake. you need to measure the average voltage, so that would be done with a DC range. A digital meter would not work, and it would be hard to do it with a microcontroller also.