INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Cannot get output from my Eurotherm controller

Cannot get output from my Eurotherm controller

(OP)
I am using a Eurotherm 3504 controller to controll a valve based on input pressure.

See details:
PV – Pressure transmitter input (0-5 bar), 4-20mA (i/p to controller)
Module 1 – Remote setpoint (0-5 bar), 4-20mA (i/p to controller)
Module 2 – Analogue output of valve actuators position to control room (0-100%), 4-20mA (o/p from controller)
Module 3- Analogue output to valve actuators (0-100%), 4-20mA (o/p from controller).

---Proportional action with gain of 40%/bar

(I interprete this to mean ...a 1 bar change in pressure results in 40% valve movement when proportional acts on its own. This gives a gain of 2 and PB of 50% I believe).

---Integral action time – 300 secs
---No derivate

Problem: I do not get any response in the output. Modules 2&3 are both reading their lowest vales – 4mA as output, which corresponds to 0% open in the actuators.

I am using a set point of 2.5 bar (midway of the 0-5bar pressure transmitter scale). When I vary the i/p current I am using to simulate the PV, (4-20mA), I do not get get any output in the valves.

Have I got my interpretation of the PB wrong?

I wish I could post screen captures here.

RE: Cannot get output from my Eurotherm controller

"I wish I could post screen captures here."

You can; the button below does that

TTFN
FAQ731-376: Eng-Tips.com Forum Policies
[IMG http://tinyurl.com/7ofakss]
Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers


Of course I can. I can do anything. I can do absolutely anything. I'm an expert!
There is a homework forum hosted by engineering.com: http://www.engineering.com/AskForum/aff/32.aspx

RE: Cannot get output from my Eurotherm controller

Output driven in one direction off scale is a symptom of the wrong control action.

Is the existing control action reverse or direct? Have you tried changing to the opposite control action?

RE: Cannot get output from my Eurotherm controller

(OP)

Hello,

I have been able to get the valves to move, thanks to the explanation below

-----------------------------------------------------------------------------------------------------------

Proportional Band: The amount of change in the controlled variable, expressed in engineering units, required to move the actuator from one end of its stroke to the other.

%PB: Percent proportional band is the proportional band expressed as a percentage of the sensor span.



-----------------------------------------------------------------------------------------------------------

I had previously set the PB as 2.5%, instead of 2.5 eng units.

All is fine now.

Thanks a lot.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close