From time to time there is a need to completely remove power from the Accel-RF (ARF) AARTS systems for such events as installation or maintenance of the UPS, moving the system, accommodating facilities shutdown events, etc.
ARF recommends leaving the system powered up at all times. Certainly during a life test run it must be powered by definition. However, even when a test is not being performed it is better for the hardware to remain powered at all times. The reason for this relates to system stability. The specifications for system performance are only valid after the system has been powered for 24 hours. The electronics in the system, particularly those related to measurement accuracy are temperature dependent. Due to the density of electronics it takes some time for the entire system to thermally stabilize after power up.
Further, there are long-term drift effects that also play a role. After the system has had power cycled many of the calibration parameters, most notably the Bias Current Offsets on legacy PCU boxes must be recalibrated. RF components are another set of devices that experience notable annealing effects and longer term drift issues. Hence, performing a new RF calibration is also recommended after cycling power.
Please reference our app note Shutdown and Startup of the AARTS System Hardware for full instructions.