Sinking Output?

I have an application for a sensor that calls for a Sinking Output. I
am not familiar with electronics. Can someone help me understand what
this means.

Thanks

 

[JeffM]

I have an application for a sensor that calls for a Sinking Output.
...help me understand what this means.
MROPART...@comcast.net

To "source" something means the juice comes out of your device.
To "sink" something means the the juice comes out of a source,
through the load (if there is a separate load),
and through your device to ground.


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[Chris]

MROPARTNER@comcast.net wrote:

I have an application for a sensor that calls for a Sinking Output.
I
am not familiar with electronics. Can someone help me understand
what
this means.

Thanks

Hi. A current-sourcing output will source current, a sinking output
will sink current. Sourcing outputs are also called "PNP" and sinking
outputs are also called "NPN". Here's the details.

+24V
..-------------------o---o
"Sinking"| |
NPN | |
Sensor | .-.
..------o---. | | R
| | | |
| .--o-----. '-'
| | | | |
| | | | | OUT
| |/ | '---------o---o
| -| | <------
| |> | I (sink)
| | |
| | |
'-------o--'
|
'----------------------o
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

Here's a "sinking" NPN sensor, say, a proximity switch. Internally, at
the output of the sensor is an NPN transistor. When an object comes in
proximity to the sensor, it is made so that the NPN transistor at the
output turns on, "sinking" current to GND. When the transistor is off,
no current flows and you can read a voltage close to or equal to V+ at
the output because of the + referenced load (R). Sensors of the
"sinking" or NPN type are more common than sourcing.

These sensors work well with programmable controllers, which have
optoisolators built in which have their commons tied to V+, like the
resistor above. They can sometimes be used with logic level power
supplies, and can sometimes be connected to logic inputs, but you have
to be careful and read the sensor literature. One big problem with
this type of output is that it is somewhat susceptible to electrical
noise when the transistor is off (false ON). Also, note that usually
these sensors have small signal transistors at their outputs, and can't
switch more than 50 to 100 mA. Also, do not use these to switch relays
or non-resistive loads -- inductive kick can crash the output
transistor. Since it's built-in and non-repairable, that means you've
got to throw the sensor out.

Possibly if you ask for an "NPN-type" sensor you might have more luck.
Or, if you can be more specific as to your sensor requirements, someone
can recommend something for you on this newsgroup.

Good luck
Chris