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Industrial Equipment Datalogging: Best practice for interfacing signals


Immediate Need: Better cables and connectors to interface industrial machine signals with DAQ

I have been using DAQ units for years to characterize, troubleshoot, improve and verify electro-mechanical behaviors of industrial equipment, primarily in Packaging industry, with great success. DAQ is always external, portable and temporary, never part of the process. Wheel it up on a cart, then put away. Problematic for me has been interfacing (non-NI) DAQ with machines, most of which are PLC-based. I find myself with a hodge-podge collection of field wires and cables (from control enclosures, external instruments e.g., pressure transmitters, thermocouples, encoders, PLC I/O, etc.) at a crude patch panel near the DAQ. Too much time is spent tracing connections, fastening wires to terminal screws, retracing connections, and occasionally, rerouting DAQ wires because they picked up machine noise.

Short of better advice found here, my plan is to:

1. Design and fabricate custom patch panel that handily interfaces up to 32 field devices with DAQ. Plug-n-play.
2. Find a durable, shielded twisted pair cable and associated connector for interfacing field devices with patch panel
3. Find shielded twisted pair cable to patch incoming field signals with DAQ at the patch panel

Immediate need is two-fold:

1. Field Interconnection (mostly 24VDC or less, 10-50ft in distance, less than 10Khz)
a. What is best cable for connecting field devices to DAQ patch panel (e.g., shielded twisted pair)?
Needs to be small jacket diameter, yet durable. Can be premade, or be plain cable with one pair, or a cable series with added pairs.
b. What is best connector for this cable? I've used 3-pin, 4-pin, 5-pin M12 connectors... is there something better? Lemo makes great stuff but very pricey

2. Patching Signals at Patch Panel
a. What connectors are best for patching? 0.1" pitch? Mini-banana? Mini coax? other?
b. Are there standard breadboard jumpers for this?

I am not a board designer but expect to find someone who can lay out a patch panel PCB (not asking for that help here). Given time, I could do myself, but would likely incur one or 20 mistakes (e.g., trace routing produces noise!!) before getting it right. Again, just giving you an idea what I am planning, custom PCB patch panel should do the following:
a. Distribute external +24V, +12V and +5V DC power to operate various connected field devices
b. Provide multiple channels of 250-ohm current loading (4-20mA field device ouputs are common)
c. Provide multiple channels of voltage dividing to adapt 24V digital devices with 10VDC DAQ
d. Provide piggy-back connector scheme to accommodate thermocouple interconnection
e. Provide standard connector scheme to interconnector with standard NI C-Series I/O cables

I don't want to recreate the wheel. Somebody here must have pioneered this long ago. All help is most appreciated.  This is my first post, feel free to correct my etiquette and/or redirect me to another forum.


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Hey Sharker1, 


I may not be able to give you any recommendations regarding your custom cabling and interface, however if you are even considering some of our NI products (besides the DAQ you already have) feel free to call into our sales line 877-387-0015. If there are any specs and requirements that they are unsure of they can make you a service request and that would be a better avenue for getting your specific questions answered as long as they involve NI products.


If you require assistance beyond the scope of our products then I would say you've posted in the right place and hopefully you can get some help here. 


Best of luck.

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