Today we are gathered here to impeach a major industrial controls manufacturer for lacking some basic common sense. I submit to you, the jury, some documentation from the installation manuals for slices of distributed input/output.
Figure 1 shows an analog input module with two inputs. Note the wiring terminals run down the left for channel 0 and down the right for channel 1. The LED indicators above them are stacked, with 0 on top of 1. This is not too badly laid out; it's a sort of vertical flow.
Figure 2 is a four-channel discrete input module with diagnostic points. The wiring for this module runs vertically, and so do the LEDs above them. This is very intuitive, in my opinion.
Figure 3 is a four-channel discrete output module. Note that the LEDs continue to run vertically, but the wiring terminals now run horizontally. What happened? Why change? This four-channel module could easily have been done the same way as shown in figure 2.
Figure 4, from the same family as all three previously shown, is now presented to the jury. This eight-channel output module has two ranks of LED indicators on top, arrayed vertically (0 through 3 on the left and 4 through 7 on the right). But the wire terminals are laid out horizontally.
Now, figure 4 calls into question the intuitiveness of the module shown to the jury in figure 1. It shows modules can have LED indicators side by side. The module in figure 1 would be better for users if the LEDs were side by side. The wire terminals in figure 3 would be more useful if the output terminals were vertical on the left and the common "C" terminals on the right. The output module in figure 4 would be better if the wire terminals ran vertically to match the LEDs.
The rest of the family shows the same seemingly random arrangement of wire terminals to status LEDs. Unfortunately for OEMs, integrators, and end-user maintenance crews, this I/O family comes from a manufacturer very popular with end users. This lack of common sense (not making LED configuration match wiring configuration) leads directly to installation and troubleshooting mistakes.
Remember that figures 1 through 4 are diagrams. The terminal numbers that look so prominent in black are actually the same color molded into the terminal blocks. They're very small. They're very hard to see in electrical enclosures.
I ask you, the jury, to find this manufacturer guilty of having no common sense. This causes mistakes. Mistakes can cause damage. Damage costs money. Unfortunately, this court cannot levy fines against the defendant, so I ask the jury to impose the severest penalty possible: ridicule by the defendant's customers.
In all seriousness, now, what were they thinking? Were they thinking?
The best answer I could get from a representative of this manufacturer was "The electronics module [the device with the LEDs] was made by one branch of the company, while the base and terminal block were made by a different branch." Fine. I can see this happening when you design by committee. But where was the product line manager when this was presented? Why didn't he send his two different branches back to the drawing board, hopefully with a single unified plan this time?
The answer to any "why" question we might have here is always going to be money (as in, it would cost too much to retool at this point of the design). Instead, they've passed what would have been a one-time cost for them down to all of us, to be incurred again and again.
I'm not asking for foolproof design. But neither do I want a manufacturer actively sabotaging what should be a simple and consistent assembly.
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