PXI R Series PWM Behavior

[blackburnite]

Hello,

I created a simple PWM using a PXI 7851R and it was working fine for the past month or so however now it is behaving oddly.  Previously if I provided a min and max output, the generated pulse would be between those two values.  Now what is happening is the generated pulse is always centered over zero with a min and max value equal to half the range between my entered values.  So for example if I wanted a pwm signal from 0-6V, I previously would enter a min of 0V and max of 6V but now that results in a signal from -3 to 3 "[ (6V-0V) / 2 ]".  As you can see in the snippet, all I'm doing is updating the AO channel with the max value, waiting, then updating it with the min value so I can't figure out why it is behaving this way.  I'm using an SCB-68A connector block so I thought maybe the switch settings got messed up but they appear to be set to direct feedthrough.  Any ideas why this is occurring?

- Will

[sassyaspy]

Hey Will,

Was this constantly running, or did you rebuild the FPGA VI recently? Does the program exhibit different behavior when you leave 0 V and 6 V as a constant instead of a control? Also, what are you using to measure the output and where?

[blackburnite · Accepted solution]

One of the AO channels on another connector block was shot previously so I was thinking this was a similar problem but it was actually just some plain dumb user error on my part and I forgot to put my scope in DC mode .