Seaward Solar (seawardsolar.com) offers the 100/200R Solar Survey meters, which measure solar irradiance, ambient air and module temperature, and array orientation and tilt. Determining that a module or array is performing as it should can be difficult, as a PV module’s voltage changes with cell temperature and its current varies with irradiance. These meters provide watts per square meter and temperature readings that can be used in calculations to compare predicted and actual power output. The array orientation and tilt can be useful for estimating and verifying energy output. The irradiance meter also displays Btu/hr.-ft.2, useful for checking the performance of solar heating systems.
The 200R model has data-logging capability, with a USB interface. It can send measurements wirelessly to a PV150—Seaward’s Solar Installation Test Kit, which tests open-circuit voltage, short-circuit current, and conductor insulation resistance (used to detect the potential for ground faults). Seaward also manufactures the Solar Power Clamp for measuring inverter efficiency.