Above Table 3 on Page 5 of the manual where it talks about Test Equipment, it states that "If you do not have the recommended instruments, use these specifications to select a substitute calibration standard." It sounds like the 5720A meets these specifications and the board is calibrated. If the accuracy of the 5520A does not meet requirements, I would not recommend using it, even if the signal is cleaner.
Josh Y.
Applications Engineer
National Instruments
