what is this symbol on the circled portion of the multimeter in the picture I attached, what is it for testing?
Answer I cannot say without knowing which meter you have, but that is the symbol for a square wave.
Many new meters have a low voltage square wave output and since it is next to the output for diode testing and grouped with it, I expect it is an output.
Check your manual. Contact the manufacturer.
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Licensed Philadelphia electrician serving Delaware, Chester, Montgomery and Philadelphia County in Pennsylvania. I install and repair residential, commercial and industrial wiring and lighting. Troubleshooting and repair of problems that stump other people is my favorite. I am willing to help people figure out why things don`t work. I understand motor controls, transformers and machine wiring.
I do not teach basics to novices or do free design work.
Experience in the area
I have 44 years experience in residential, commercial and industrial electrical construction and repair, 480 volts and below. This is not to be confused with one week repeated two thousand times.
Education/Credentials 44 years experience in residential, commercial and industrial electrical construction and repair