Solar testing equipment is used to monitor the efficiency of your solar panels and detect whether they are worn out or faulty.
An 'I-V curve' is the relationship between current and voltage in an electrical device or component. Solar testing equipment allows you to monitor the parameters of this relationship in your solar panels to determine whether they are working correctly. It can then provide you with an efficiency calculation, sometimes in the form of a percentage.
Solar testing equipment varies by size, minimum and maximum operating temperatures and minimum and maximum voltage measurements. Some can monitor current to a greater degree of accuracy than others, and can have different capacities for logging data. You may be able to download via a USB connection, or you may be able to send it straight to your smartphone. Solar testing equipment usually has rechargeable batteries and an LCD or LED display.