A question about using ferrite chokes in a data-acquisition system

Question

I'm planning to buy [this flat ferrite choke][1] for ribbon cable to suppress suspected EMI on a data acquisition's multiplexer.

I have no experience on signal integrity. Bu the system setup is basically like this(On the right side the system is single-ended earth grounded):

Instead of adding chokes to each BNC I thought it would be easier to use just one flat core for the ribbon cable since it conveys the signals to ADC insdie the PC.

Which would be a better option? To apply chokes to each BNC cables or to use one flat ferrite core around the ribbon cable? I also couldnt find any passive chokes for 50 Ohm coaxial BNC cables in the market until now, neither info how to install them.

I'm having random glitches sometimes. By random I mean 2 or 3 times in 30 minutes acquisition. And this is not every time. By glitch I mean at some point suddenly all the channels are affected. So it is almost impossible to observe this by scope because I don't know when the noise will hit.

Answer 1

All channels simultaneously get a value of 0 – that's most definitely not EMI, or any other type of what I'd call "noise".

That's a problem with your sampling hardware. Now, this might be anything – from a driver bug to a hardware fault, to samples not being fetched before some buffer runs over to some problems with a on-board power supply, or, and that's my current guess: a faulty connector somewhere that randomly makes the "BNC box" power off.

Generally, if you really just need 6 channels, your bandwidths are this low and you don't calibrated voltage readings, but just relative values: Try replacing the PCI DAQ card with a simple multichannel sound card.

A single 16bit ADC that gets multiplexed across a few 4kS/s channels? That's really not that great – you can actually build that with something as cheap as an arduino. Still, it's probably more time- and cost-efficient to not build something like that yourself, but try with widely available DACs – of which soundcards are the cheapest ones, and perform surprisingly well.