How do you know if your PV array is doing its job?

I've been working on a simplified method to ascertain the state of health and
proper performance of a PV array.

On one hand, I've been developing a sophisticated system of sensors, and
web-based instrumentation to achieve a 'measured' level of performance
of a PV array and its inverters.

On the other hand, I'm devising a simplified set of tools,--protractor, compass,
level, temperature and light sensors, total costing less than a couple of hundred
dollars and basic skills of trigonometry; to arrive at a qualitative indication of
how a PV array is performing. This is based on performance parameters
stamped on the PV panel used in the array.

I'm curious as to level of interest on this method among the solar energy
enthusiasts.

Any comment, or suggestion will be welcome.