The MID-7604 puts out a lot of noise, where can I get isolated cables for it?

Question

I'm using a MID-7604 stepper motor driver. I'd like to reduce the ground loop noise in the system that I am measuring on my PXI-5152 (through a series of transducers, etc.) by using an optical or transformer isolator for the 68 pin VHDCI cable that connects the motor driver to the computer. Does such a thing exist or are there other methods to mitigate the noise? I'd prefer to have the MID-7604 and the computer connected to the same circuit/I don't really want to buy a gigantic isolation transformer/surge protector just to plug in the MID-7604.
Solved!
Go to Solution.

Answer 1

OlliesCamel,
The devices I'm using are PXI-5152 for signal acquisition, TEGAM 4040B for amplification, MID-7604 to drive stepper motors (which have specifications shown here http://www.sherline.com/stepspec2.pdf) to turn a Sherline rotational stage. The transducers are both Harisonic I30508T 5 MHz 3.5" focus transducers.
I have scanned in a drawing I made up of how everything is physically connected entitled Electrical connections.PDF. Also, the noise I am referring to is the noise that is shown in picture noiseMID7604.jpg. (It is labeled)
For the initial laser noise I'm getting an optically isolated RS232 which should fix that problem. On the MID-7604/7602 stepper power motor drive user guide and specifications it shows on page 13 that a wire should go from the 3 position to the case for grounding. It also shows that it seems to be attached to the shield of the shielded wire. Is this necessary as long as I have the ground connected to the case of the motor or? The way I have it now I just have a separate wire in the bundled/shielded cable that is going to the case but it isn't connected to the shielding itself.
The settings for the amplifier and the PXI are for 1 M ohm impedance.
As you can see, my signals don't have a very large SNR, so any sort of motor noise is problematic, particularly since the noise I've shown doesn't stay in the same place during the test. It tends to move around/be on top of my signals at random times even though it doesn't show that in this particular picture. It is problematic since I'm taking many measurements (20,480 acoustic signals per scan, etc.).
I've tried averaging (256 times) and filtering (10 MHz low pass filter is the lowest I can go), however, the noise still persists a bit since it happens to somewhat fall under the same frequencies, etc. The averaging does help, but I'd like to run the test faster and so eliminating that noise would help me in that regard.
Attachments:
Electrical connections.PDF ‏418 KB
noiseMID7604.jpg ‏128 KB