Read the oldest error information from the error queue. The error queue can store up to 255 errors.
The error queue is cleared using the *CLS command.
Returns the oldest error or event information in the error/event queue in response to SYST:ERR? as follows:
(Example) When there are no errors or events
Returns 0, "No error".
(Example) When a command that cannot be executed in the current operating condition is received
Returns -221, "Settings conflict".