You want to choose a voltage range capable of displaying the maximum possible voltage of the panel in open circuit this means that if you have a panel rated for 20 volts you should set the multi meter.
How to test solar panel amp output.
To begin measure solar panel amperage.
You need to have a panel tester that is known as an amp meter.
Whenever you have these two values you can figure out the wattage by multiplying them together.
To determine the power that the solar panel is dissipating you need to measure the wattage and voltage.
Attach the meter to the positive and negative so that you measure the amp output of your solar panels.
To test a 18v solar panel voltage output directly put your solar panel in direct sunlight set your multi meter to the dc volts setting.
As long as the amp meter is rated higher than the solar panel you will be able to measure the output effectively.
To get an accurate measurement you will need to ensure that your panel is in full sunlight when you test.
To measure the amp output of your solar panel you will need to attach the meter to the positive and negative.
Attach the meter to the positive and negative terminals on the solar panel and make sure the panel is properly exposed to sunlight.