Sink vs Source in relation to 4-20mA loop

When you talk about digital components, like proximity switches, a “source” component supplies power on its terminals and responds to the change in the load. A “sink” component, on the other hand, does not supply power to its terminals and responds to changes in the voltage or current impressed upon it as measured on those terminals.

In 4-20mA loop parlance, I could understand a “source” component as one which supplies the loop power such as a powered 4-20mA output card in a PLC rack, or a 4 wire pressure transmitter that provides the loop power from its internal power supply.

Likewise, I could understand a “sink” component as a passive receiver instrument such as a 4-20mA input card on a PLC, or one of the gazillion 1/4 or 1/8 DIN panel meters on millions of pieces of equipment in factories.

But that leaves a gap for a couple of pieces. In loops which have a 24VDC loop power supply rather than having power supplied by the transmitter, I certainly wouldn’t think of that as “source” instrument despite the fact that the PS is obviously supplying the EMF. Likewise, for a loop powered 4-20mA pressure transmitter you couldn’t call it a “source” instrument if the criteria are that it should supply loop power since it doesn’t supply the power. However, I also wouldn’t call it a “sink” instrument, since it isn’t a receiving instrument.

SOURCE: http://www.control.com/thread/1026233000

Want to be the first to know? Subscribe to our Newsletter!

Enter your email below and we will send you our latest content directly to your inbox. Be the first to read about topical discussions, and new product releases.

This Post Has One Comment

Leave a Reply

More-Articles-Icon-Two-Documents-Blog-News-GEO-PSI
Solving-Unique-Customer-Problems-Through-Innovation-GEO-PSI
Top Posts
Nick Nazarovs

Solving Unique Customer Problems Through Innovation

A look at how continued capital investment enables us to develop innovative solutions for unique customer problems. In a previous blog post of ours titled Getting Off The X”: A Lesson in the Value of Movement, we put forward the idea that movement in business, or your personal life for that matter, positions you for

Read More »
Service-Installation-And-Maintenance-World-Wide-Oil-Rig-Oilfield-Trucks-GEO-PSI
Archive
Jeff Scott

Permanent Downhole Gauges & The Importance Of Accountability

ac·count·a·bil·i·ty [uh-koun-tuh–bil-i-tee] I’m often asked, what does GEO PSI do? Technically we manufacture, install, and service continuous downhole pressure monitoring systems. While that may be interesting, there are at least 20 other companies in the world that can claim the same. “I believe what makes us unique is that we are actually selling accountability to our customers.”

Read More »
Technology-Partner-vs.-Product-Vendor-GEO-PSI
Top Posts
Aastik Saluja

Technology Partner vs. Product Vendor

A look at how our approach of becoming a technology partner differs from product vendors or service providers. Here at GEO PSI we strive to develop fit-for-purpose, robust, and cost-effective downhole monitoring technologies that provide immense value to our customers. Our Vision “To provide digital oilfield solutions to energy producers for environmentally responsible full field

Read More »