I have been looking for the front panel controls to control the DAC voltage out the back of the PNA-X I/O. So far, I have not been able to find them. I want to make S-parameter measurements of a voltage-controlled device at a single frequency. I want to sweep the voltage over a subset range of the +/-10 volt range, and display the result with the applied voltage on the X-axis, and one or more S-parameters on the Y-axis. How do I set up the instrument to do this?