recondaddy
Member
I hope the triviality of this question doesn't betray my experience level, but I'm just starting to get into safety system design, and this question, while always bouncing around in the back of my head, has now taken on some significance.
I understand what normally-closed late-break (NCLB) and normally-open early-make (NOEM) mean, but why do we care? What do these particular distinctions accomplish that make them so much safer than standard NC and NO contacts?
Thanks.
P.S. For those who may never have heard:
NCLB contacts remain closed until the operator is fully mechanically latched. For example, when you push an e-stop pushbutton, the contacts stay closed until the pushbutton reaches the fully pressed position.
Conversely, NOEM contacts close BEFORE the operator is fully mechanically latched. So, when pulling an e-stop pushbutton back out after pressing it, the normally-open contacts will close BEFORE the button has reached its fully pulled position.
I understand what normally-closed late-break (NCLB) and normally-open early-make (NOEM) mean, but why do we care? What do these particular distinctions accomplish that make them so much safer than standard NC and NO contacts?
Thanks.
P.S. For those who may never have heard:
NCLB contacts remain closed until the operator is fully mechanically latched. For example, when you push an e-stop pushbutton, the contacts stay closed until the pushbutton reaches the fully pressed position.
Conversely, NOEM contacts close BEFORE the operator is fully mechanically latched. So, when pulling an e-stop pushbutton back out after pressing it, the normally-open contacts will close BEFORE the button has reached its fully pulled position.