Switch Power Calculation for Pulsed Signals

Issue Details

In the specification sheet for the PXIe-2737 , there is a description that explains the maximum switching power is 60 W, 62.5 VA. I am using a pulsed signal with a duty cycle of 5 % with 84 Vpp and 2 A. Can the switch handle these pulses? Does the duty cycle factor affect the perceived power from the switch's perspective? Can we calculate the signal power as 84 V * 2 A * 0.05 = 8.4 W? 

Solution

When handling a pulsed signal, you will have two states. Either on or off. When the signal is on, the switch perceives the full power, which would be 84 V * 2 A = 168 W. This value is too high for the card and shouldn't be route through the switch. Therefore, even if the duty cycle changes the average power of the signal as a whole, from the switch's perspective, you cannot multiply the power by a duty cycle factor.

In addition, in some cases it might be possible to carefully time the signal and the switch's operation to only toggle channels during the low part of the signal's duty cycle. However, the relays generally take a couple of milliseconds to toggle. Therefore, it is strongly recommended to pause the pulse before toggling the relays.

Additional Information

While this article addresses the PXIe-2737, the same logic applies to the family of switch devices.