What happens if sensor is disconnected during operation of FLXA402, SA11, and sensor? Will the measurement value be kept on hold?

It will be an error. This is because it is not possible to know whether SA11 has been disconnected or communication error has occurred due to cable disconnection. Burnout function will be active when SA11 is disconnected. If you want to avoid burnout, please change in advance mA output setting to hold.