I'm trying to inject a signal and read 2 voltages using the analog output and input portsof USB 6003 using LabVIEW. I use the digital I/O to control relays to move the signal to different points in my test circuit. When I run this through once, it works fine. The problem comes when I try to run my VI in a loop. It makes the readings I tell it to for the first point, but when it loops I get an error saying the buffer needs more time (or something to that effect). So, what am I doing wrong? How can you clear the buffer? I've attached my VI's, Test2A is the main VI and CurveTrace is the sub.