Phase Lock problem with a PXI-1000 chassis

[chilly_charly]

As already discussed here, we had an application running smoothly on a 1042 chassis with a 8186 controller.

We generate two sine waves in phase quadrature, using two 5411 boards.

Unfortunately, we are now obliged to use a PXI-1000 with a 8170 controller, and we don't get anymore the expected results : the signals are generated with the correct frequency and amplitude, but the phase offset is totally unstable, as observed on an oscilloscop.

We are using the Synchronized wave generation NI example. Are we missing something ?

Please consider that we are not specialists in electronics, just plain biologists :).

We need help URGENTLY !!!

[Kenny_K]

One thing that I noticed between the 1000 and the 1042 is that the 1000 has the Fan integrated with the power supply, so the fan is probably run off AC.  In the 1042, the fan is run off DC and as stated in the specifications greatly reducing electronic noise.  It could be that your phase offset is caused by the AC fan in the 1000.

You might want to try to move everything as far away from the power supply and fan as possible (if it is possible) to see if this helps at all.

Also, the 1042 and 1000 have a 10 MHz reference signal for timing pusposes to each of the modules.  The 1042 has an accuracy (skew) of 250 ps between each of the mudules.  The 1000 has a skew of 1 ns, obviously much greater of an error (less accurate), which could be causing some issues as well.

I do not know what freq you are operating at, but you may be able to filter some of the 60 Hz frequencies out with a smaller capacitor 0.1uF or so.

Good luck.

Kenny

[chilly_charly]

Hi Kenny

The problem was with the PXI-1000 chassis. We tried every solution, slots permutation, far on the right, far on the left,... even considering that one of the 5411 boards could have been damaged in the exchange process. We ultimately found that the problem was with the RTSI clock. We have changed again the chassis, for something else (don't ask which one, it's something old and rusty..., and things are again running properly.
Thanks for trying to help.