We are using the 6211 in a custom power supply design. The 'left hand' side is connected to a standard lab signal generator via a 50 ohm cable that is powered from 120VAC. The 'right side' is connected to an FPGA that is used to control a Dc-Dc converter that is powered from 240VAC. The device is being driven with a 15uS signal at approx 200Hz. both sides are capacitvely coupled to chassis / earth. The device will only trigger if the pulse generator is outputting 5V pk-pk pulses with a 2.5V offset and does not work with 5V pk-pk with a 0V offset.
I suspect that there is a capacitive ground loop connection between the pulse generator and the 240VAC power supply via out power supply and the earth connection back in the breaker box in another part of the building and perhaps the ground loop is preventing the input of the 6211 from exceeding the trigger voltage. However, this really doesn't make sense as the bandwidth of the device and the noise immunity is kV/nS so it should be tolerant to noise on the input.
Clearly I am missing something - Does anyone have any insight?
Thanks in advance