Synchronize cDAQ-9174 with PXIe-1082?

[FT1989]

Hi,

I have a cDAQ-9174 using a ni-9401 module to read position of an angular encoder. I have a PXIe-1082 chassis with PXIe-6365 Multifunction I/O module reading other analog inputs. I want to synchronize these two chassis but I'm not sure what hardware I need to make this happen. The 1082 backplane has BNC connections for 10MHz ref clock. It seems like I need an NI-9469 for the cDAQ with CAT5 cables, but it only  connects to other NI-9469 modules. I understand a cDAQ-9178 would have BNC connections on the chassis but is there a workaround for a cDAQ-9174?

This is an attempted solution to an issue I've been having the angular encoder being on the PXIe-6365 module. If the encoder is connected to the PXIe and powered on, the other signals on the module become extremely noisy, such that the data is unusable. So I disconnected the encoder from the PXIe and connected it to a cDAQ-9174, the only other daq device I have. This dramatically reduced noise in the other signals, however the data is no longer synchronized.

Thanks in advance!

[Kevin_Price]

I don't know either way if there's a workaround for chassis-syncing between your PXI and cDAQ chassis.

With that caveat, I'd be focusing harder on the original problem -- why does the encoder induce so much noisiness on your other channels of the PXI-6365?  How can you fix it?

It's far, *far* more common for people to be able to readily integrate encoder and analog measurements on the same MIO device.  Your situation is unusual, not the norm.  That makes me think it can probably be fixed/avoided/worked around.

-Kevin P

[FT1989]

Hi Kevin,

I don't understand why there is so much noise when the encoders are operating.

All encoders are connected to the cDAQ-9174 now and also powered by a separate power supply. This has certainly decreased noise but it is still significant. The only common point of contact with the PXIe-1082 is the power supplies are connected to the same power strip.

If the encoders are off, all signals are excellent with high snr. The most sensitive signals I'm acquiring are hall effect sensor signals that have a range of 0.2 volts and the noise is less than 0.02 volts. When the encoders are on, the noise increases to around 0.2 volts, drowning out the original signals.

[Kevin_Price]

I'm not an expert on dealing with electrical noise, but I very strongly suspect this to be a solvable problem.  I'm inclined to think you have a particularly terrible power supply and you could help matters by using a better one.

As a diagnostic step, can you try powering the encoder with plain old batteries?  Or do you have other better quality power supplies you can try?

-Kevin P