SolarPro Magazine, Feb./Mar. 2014, by Brian Mehalic and David Brearley.
http://solarprofessional.com/articles/operations-maintenance/commissioning-and-om-tools?v=disable_pagination

"Do you ever wonder what tools solar professionals carry when they are performing quality control, commissioning, or operations and maintenance activities on commercial and utility-scale PV systems? We did—so we found out."