Sinking & Sourcing I Video Lecture | Digital Electronics - Electrical Engineering (EE)

all right so if we look at this we have
some main components are 24 24 volt DC
source a fuse field device and input
module and we need to connect the
circuit up so I can choose to show this
using conventional flow theory or a lock
on flow theory for this example I'm
going to use conventional flow theory if
I'm going to use conventional flow
theory I'm going to start off at the
positive and I'm going to come across
and I'm going to fuse the circuit
remember this is a 24 volt DC source
it's external to the system so we're
going to fuse it and again we're going
to come down to our field device which
is just a regular switch just to show
you it's going to come through the input
now remember the external circuitry of
the input module will eventually hook up
to the common which will come down
across and back up to our negative side
and of course this side here is is to
ground right so that's our basic circuit
and again if we're using conventional
flow theory that current will go that
way now if we were asked to define
whether this field device was sourcing
or sinking or the input module sourcing
or sinking it's in relation to our main
source and the direction of current flow
so in this case if currents go in this
way around this field device will be
sourcing it's closer to the source on
the direction
so sourcing current the DC input module
will be sinking current notice how it's
after this one so this one be sourcing
this one would be sinking now if we look
at this relationship if out in the field
right here it developed a ground let's
analyze the circuit and see what's going
to happen current would flow through
here and soon as we close a switch it
would go to ground that would cause a
short circuit and this fuse would blow
and with this fuse blowing it would save
the circuit