The Fundamentals of 4-20 mA Current Loops

[@jameserayburn]

Best tutorial on 4-20mA I've seen thus far. Two big thumbs up.

[@predig]

Glad you found this useful James. Let us know if there are other topics you'd like to learn more about as we may consider them for future webinars.

[@andersonmauricio209]

sorry to be off topic but does someone know of a tool to log back into an instagram account? I somehow lost the password. I would love any help you can offer me.

[@tobywade776]

@Anderson Mauricio Instablaster ;)

[@andersonmauricio209]

@Toby Wade thanks for your reply. I found the site through google and im trying it out now. Seems to take a while so I will reply here later when my account password hopefully is recovered.

[@guyems8693]

5:02 Is Intro 10:38 Where it starts

[@chriscrawley1014]

Surprised there wasn’t many videos on this subject. However you guys nailed it! Thanks for the info.

[@predig]

Thank you for the feedback! Glad you found our video useful.

[@randallnicholas1848]

9 Year Old Video and it is still very informational and appreciated!

[@predig]

Thank you for the feedback! Glad you found this useful. The video may be old, but the fundamentals discussed remain the same.

[@youtuuba]

As a retired electrical/process engineer and also college professor in the industrial control curriculum, I tend to watch a lot of videos like this; I am interested in what the presenters do well, and what they do poorly. How well do they address the questions from the students. Sometimes, it is obvious that the presenter has given their 'class' many times and had learned from the experience, refining how they present the information. Most of the time, it seems as if the presenter is still new to the subject, and falls into a lot of holes in trying to convey the concepts adequately. I thought this video started pretty well, but then started to fall part when students started asking questions. For example, when one student asked "what does regulating the current" mean, the presenter repeatedly tried to use the word "regulate" to define itself, which never works. When I taught this subject, I usually dealt with this question by making the points: - Without a Transmitter, we could just adjust one resistor in the loop until the desired current flows, and the Receiver(s) will 'see' the correct value. But if the loop resistance changes for any reason, or if the power supply voltage varies by even a tiny amount, the loop current will change and thus the Receiver will no longer see the correct process value. - To make the current loop reliable, able to cancel out or ignore all the odd variables in the environment or in the loop equipment and wiring, we introduce the Transmitter. - The Transmitter acts as a variable resistor in the loop, and its resistance gets changed automatically by the Transmitter in order to cause the desired current to flow in the loop, such that the Receiver(s) see the appropriate process value. But by itself, this function of the Transmitter is little better than the first rough (no Transmitter) approach. - To really make the current loop work robustly, the Transmitter ALSO incorporates its own Receiver, just like all the other Receiver(s) in the current loop. Since the loop current is exactly the same everywhere in the loop at any given point in time, the Transmitter's integral Receiver sees exactly the same current as all other Receiver(s) in the loop. Now, if the Transmitter means to have, for example, 12mA in the loop to represent a 50% process value, but some environmental change, or loop resistance change, or the power supply voltage changes, this tends to move the current away from the desired 12mA, but since the Transmitter instantly sees the error via its integral Receiver, it can tweak its variable resistance to counteract the error and get the current back to the intended 12mA. This correction happens essentially at the speed of light, so there is no perceptible delay and for all practical purposes, there never was an error in the first place. THIS is what "regulating" the loop current means.

[@muhammadhabibalkhairi7946]

Thanks for this explanation

[@mushwani85]

this is an excellent piece of video , a really appreciate you for such deliberate effort, here it subscribed.

[@merlissoto3923]

Excelente webinar. Aunque no participé en tiempo real, fue una clase excelente. Muy instructiva. Thanks very much for this excellent instructive video.

[@predig]

Merlis, nos alegra saber que este webinar te parecio instructivo. Tendremos más webinars en el futuro, incluso en Español. Visita www.predig.com/webinars para mas detalles.

[@cranebert7058]

thank you, in farming i am starting to get involved in measuring all this, transducers, water levels, vfd's, great job, thanks

[@predig]

Glad to hear you found this webinar useful!

[@garbo8962]

PM I'd hundreds of VFDS from 5 to 200 HP. but never got involved with the speed control. Never asked what is the best control & most commonly used the 4 to 20 milliamp or 4 to 10 millivolt.

[@oketchojacob9826]

Hello there, suppose that the pressure transmitter is used on both sides of a unit to balance the pressure across the main inlet valve to the turbine. Now one transmitter has failed. it is possible to bypass the two-wire device? is it safe to join the +ve voltage terminal and the feedback terminal together? Since for the unit to start, there should a balanced signal to the controller

[@ioannistsikriteas3807]

Hi, i have a Fluke 724 Calibrator and a Flow transmitter with the 24 dc voltage supplied by an external ps on it. If i try to simulate my transmitter is there a change to damage my calibrator from the dc voltage of the loop?

[@jeremyhall7951]

Shouldn't be an issue as long as you take care not to run over current.

[@jacquedreyer5479]

Really awesome video gents - thanks for sharing!

[@predig]

Glad to hear you enjoyed this video!

[@TheRealTomBombadil]

Wow, this is awesome. Thank younfor this

[@predig]

Thanks for the feedback! Hope you found our video useful.

[@sivapathasuntharamaruliah5930]

Can you please explain about receivers maximum allowable input impedance for 4 - 20 mAmp transmitter? I recently experienced a 4-20 mAmp tranmitter when connected to a data logger(0-10VDC) using 250 Ohms across data logger terminals trasmitter dropped it's output from 16-17 mAmps to 2-3 mAmps. I suspect transmitter is unable to maintain current supply depending on sensor output due to high input impedance of data logger. Please explain

[@merlissoto3923]

¿Seminarios en español? Great!!! Igual si están en inglés los disfruto y aprendo, y si hay en español no pierdo información por efectos del idioma!

[@predig]

Hola Merlis, si quieres participar en nuestro próximo seminario web sobre nuestras 3 nuevas líneas de productos se llevará acabo en Abril www.predig.com/seminario. La versión en Ingles será a finales de este mes www.predig.com/webinars.

[@Electricworld-1]

Thank you, very helpful, good information .

[@predig]

Glad you found this video useful! Don't forget to check out our white paper version here: www.predig.com/indicatorpage/back-basics-fundamentals-4-20-ma-current-loops

[@kookoo7786]

Very Good tutorial 👍👍

[@dieguyn]

Search the video with that name, is an excellent Hart Configurator: Configurador Protocolo Hart - Bluehart Eletrosert.

[@h20no63]

Great videos but audio is lacking.

[@ns-nf9pi]

subtitles seems to be "calibrated"

[@saeedlanjekar9905]

what is the voltage level in 4-20 mA current in flow meters

[@SuperHaptics]

A pedantic comment follows 🤪. I think Ohms law is generaly presented I=V/R for showing the causality in the relationship of current to voltage and resistance. DC Current in basic terms exists as a result of voltage and resistance. However voltage exists without any current being present... So even if that presentation is algebraicaly correct, i think the original order should be kept when describing ohms law principles i.e.what is causing what and how they are related.

[@jmhealey9432]

wow thanks! This caused me to think like an engineer (which I am not) instead of a technician ( which I am )

[@velmuruganrajesh8240]

How to running Fuji frenic ac drive 4 to 20 mA pressure feed runing

[@ClaudinneV]

Thank you very much! Very insightful :)

[@predig]

Glad it was helpful!

[@mihaiadam4024]

great job, thank you

[@predig]

Thanks for the feedback! We're glad you enjoyed this.

[@zynthos9]

38:30 Why would there be a voltage drop when using a 0-10V or 1-5V signal as opposed to a 4-20mA signal? The thing that causes the voltage drop is current, yes? If you are using a voltage signal (no current) how could there be a drop across long wires?

[@ricky36975]

Signal does not have anything to do with the loop in question, by signal he means the reading you are measuring in the loop. So since a powered series circuit has a consistent current flow for the entire circuit and a changing voltage after resistance, he is saying you want to measure the current and compare that measurement to your power source. This is because if you don't you can measure for voltage at several different places of an unchanged circuit and you will get different voltages. To sum that up, it is a property of a series circuit that could screw you up if you aren't thinking about it.

[@greywolf271]

Any circuit feeds into a load, however high the impedence (or resistance) of the load is, it draws current from the input circuit. You assume the input signal will not cause current to flow. This is wrong.

[@emslawrenceks6108]

Good Stuff A++++

[@selfhealing1047]

Calling from the Moon

[@surzsanz3988]

what time is it? 4.20? wait..... i shouldn't be here

[@jhariasaurabh75]

I wish audio quality was a little better

[@balikuddembejoseph1519]

Manufacturing

[@balikuddembejoseph1519]

Africa

[@KDNACH1]

too slow...boring! get to the point

[@hiramkhackenback]

true, 10 minutes before any content was started

[@chriscrawley1014]

Surprised there wasn’t many videos on this subject. However you guys nailed it! Thanks for the info.

[@predig]

Glad you liked it! Thank you