ControlLogix Module Selection

bledet

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Join Date
Mar 2007
Location
New Orleans
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What are the advantages of using the modules with less I/O points such as:
1756-oa16 vs. 1756-oa8
1756-of8 vs. 1756-of4

Why would you use two 1756-of4 insted of one of8? Is there a pogramming or reliability advantage I am overlooking?
 
OA8 is 2A per point, OA16 is only 0.5A per point.
OF4 and OF8 pretty much the same functionality, just have different amount of channels, so if you need just few channels why pay for 8. But it makes no sence to buy two OF4s
 
Contr_Conn said:
OA8 is 2A per point, OA16 is only 0.5A per point.
OF4 and OF8 pretty much the same functionality, just have different amount of channels, so if you need just few channels why pay for 8. But it makes no sence to buy two OF4s

It makes sense if you need one point at the time of installation and four more sometime down the road.
 
It may also make sense to use two OF4 cards if you have many systems that use a single OF4 and don't want to stock two different spares.

But now we are nit-picking...
 
jimbo3123 said:
It makes sense if you need one point at the time of installation and four more sometime down the road.

If I am building a custom system I usually go with the spare I/O, but OEM's build the same thing over and over and if you save a few dollars on each machine it can add up to be siginificant after you've built a hundred, or it helps to make your price more competitive.
 
Thank you everyone for your input. I now have tyhe answers when they hit me with the q's.

OkiePC - Actually your nit picking is right on the money. They want their new systems modules to be compatable with an existing systems modules, for stocking spares, to save $$ . I just can't justify that excuse for an extra 5-7 I/O modules, cables, IFM modules, chassis slots, panel space........ After all of that, their savings sure are costing alot, now aren't they!
 

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