AMETEK XG Family Programmable DC - Manual (Page 336)

APPENDIX B
Error Messages
B-6 M370430-01 Rev E
Query Error List
An error number in the range [-499, -400] indicates that the output
queue control of the instrument has detected a problem with the
message exchange protocol described in IEEE 488.2, chapter 6. The
occurrence of any error in this class causes the query error bit (bit 2) in
the Event Status Register to be set.
Table B-4 Query Error List
Error
Code Error Message Description
-400 This is the generic query error for the power supply, used only
when the other types of errors do not apply.