I am pasting an answer that was asked a while back that may help answer yours.
Title:
Error 10086 When Using Calibate_E_Series Function to do an External Calibration.
Problem:
In this particular case, the customer was trying to do an external calibration on his E Series board using the E Series Calibration Fixture to connect a power supply and DMM to the board. He made the following NI-DAQ call, "Calibrate_E_Series(2, nd_ext_calibrate, nd_ni_sw_area, 6.1)", but received error 10086, "Invalid reference voltage".
Solution :
This customer was trying to use a power supply to provide the external reference voltage to calibrate the board with. However, a power supply cannot provide a steady enough signal for NI-DAQ to be able to narrow in on a value. A
source 4 to 10 times more accurate than the board should be used, such as an actual calibrator.