Jay,
I cannot give details about the way the power supply VIs work because I do not have them.
Generally when an instrument software is initialized, the instrument is set to a "safe" and known state. Typiclaly for a power supply that would be with the output voltages disabled or set to zero.
If you just put the ELVIS power supply in a loop, it would initialize and close the power supply every time the loop iterated. You do not want that. What you want is Initialize, change output voltage until limit is reached, then set voltage back to zero and close. There are two common ways to do this:
1. Create three subVIs. One does the initialization. The next sets the voltage. The third closes. Looking at the VI names, it appears that these already exist. So the existing power supply VI has this structure. The only difference is that it is set up for manual operation rather than for use as a subVI. More on this later.
2. Create a state machine program. States include (among others): Initialize, Set Power Supply, Calculate Next Voltage, and Shutdown. It would start at the Initialize state. After initialization it might go to an Idle state to wait for the user to start the experiment. Then it loops Calculate Next Voltage, Set Power Supply, repeat, until the end voltage is reached. Then it goes to Set Power Supply with the voltage = 0 followed by Shutdown.
Further comments on converting the existing Power Supply VI: Make the initialization subVI from the stuff to the left of the while loop which is relevant to the power supply. Remove all the property nodes, because the front panel will not be open while it is running and the User Interface (UI) stuff is irrelevant. Inside the loop the event structure in the Idle case will be removed - but - carefully as some of the code inside it is still needed. It looks like the Timeout case code needs to run at least once. Perhaps this should be moved to the initialize subVI outside the loop. The update VI may be all you need in the loop. I cannot be sure, again because I do not have the code. The VI needs some new controls: Start Voltage, Step Voltage, and Stop Voltage. Some error checking to make sure that Start + N*Step will reach Stop for some N. Connect Start to the left terminal of a shift register. After writing to the update VI inside the loop, add Step to the value on the shift register and wire it to the right terminal of the shift register. Stop the loop when the Stop voltage is reached. Note that you need to account for both positive and negative voltages.
Lynn
