20mA current loop

[den2k88]

Never used a current loop but multileveled PWMs are quite common.

GCS/GE d--(d) s-/+ a C+++ U+++ P-- L+@ E-- W+++ N+ o+ K- w+++ O? M-- V? PS+ PE Y+ PGP t+ 5? X R+++ tv-- b+(+++) DI+++ D++ G e++ h--- r+++ y+++*      Weapons extension: ma- k++ F+2 X

[0x01AA]

Before about 35 years I was in contact with 20mA current loop. We used it because it was easy making galvanic isolation.

[Lost User]

CodeWraith wrote:

I think that current loops are now a thing that you can find in a museum, or am I wrong there?

Lots of hardware in the maritime industry still using current loops today. Kongsberg, Baker Hughes, Hatteland, Rolls-Royce... many others, too many to name.

[dan sh]

0x01AA wrote:

Before about 35 years I was

...not existing on this planet in this form.

"It is easy to decipher extraterrestrial signals after deciphering Javascript and VB6 themselves.", ISanti[^]

[CodeWraith]

Ah, ok. Reliability instead of shiny and new. Makes sense.

I have lived with several Zen masters - all of them were cats. His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.

[honey the codewitch]

CodeWraith wrote:

I just stumbled over an old construction article where an option to use a 20mA current loop instead of RS232 is included.

I actually run into things that use serial in the IoT realm and while i'm usually using a USB to serial bridge like a CP2102 or a CH340, some little devices break out to RS232. The thing is, I have no idea what a 20mA current loop is or why it could replace the functionality of a serial interface? And it's something I feel like maybe I should understand. What sorcery is this?

To err is human. Fortune favors the monsters.

[CPallini]

Cobol is still used, my dear.

"In testa che avete, Signor di Ceprano?" -- Rigoletto

[Lost User]

CodeWraith wrote:

Reliability

Yep, I just looked through the Raytheon and L3 products and see they are still using them too. I use to work with alot of maritime hardware. We were converting currrent loop to RS232 to interface with our PLC back then.

[lmoelleb]

Last I heard of it was the Lenz RS-Bus used in model trains - no idea if it is still used, I just read about it back 5-10 years ago. I have been tempted to hook up a remote sensor with current source to run two wires only (as an alternative to 1-wire but less prone to noise or capacitive problems on longer runs). Never got off the ground though, and I do not remember what it was I wanted to sense, so it was probably not important. :)

[CodeWraith]

Old and ancient magic, used for teletypes and later for computer terminals. As an old standard, it was slower than RS232, but is also known for its high noise immunity.

I have lived with several Zen masters - all of them were cats. His last invention was an evil Lasagna. It didn't kill anyone, and it actually tasted pretty good.

[Lost User]

CodeWraith wrote:

also known for its high noise immunity

Cable length[^] is a limiting factor for RS232. Also the reason why some industries are still using current loops. :)

[Mircea Neacsu]

… or RS485 I’d say current loop is confined these days mostly to analog 4-20 mA sensors

Mircea

[Lost User]

Mircea Neacsu wrote:

current loop is confined these days mostly to analog 4-20 mA sensors

Yes, I would say it's the industry standard in some areas. There are many thousands of industrial sensors using current loops even today.

[theoldfool]

Hardly qualifies as a loop but I have a current sensing switch that turns on a device when a pump starts up. Monitors the current on the AC line to the pump.

>64 Some days the dragon wins. Suck it up.