I connected several devices to my raspberry pi Zero. These devices are breakout boards for sensor and some ICs. Sometimes I suspect that one of the boards has short circuit. For example, when I modify wiring and flux residue is not cleaned properly. Thus I wanted to know, if it's possible to check whether the Pi Zero has been booted, by measuring a voltage of a node. This is for protecting my PC. Unfortunately I do not have a monitor in the location. 

I disabled LED using the boot script and may not enable it again, because the place should be completely dark, except when I go there to deal with the hardware.