Contact US

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.

Students Click Here

Sharing of Transmitters for Different Control Loops

Sharing of Transmitters for Different Control Loops

Sharing of Transmitters for Different Control Loops

Dear All,

I am seeking your views in the acceptance of good engineering practice to have a common transmitter used to send signal to two different control loops whih perform different functions. For example, a flow meter sending signal to minimum flow recycle control loop, same transmitter is used to send the flow feedback to a flow control loop regulating the same pump speed to achieve a specific set point. Do you agree that transmitter burn out would cause losing both loops and hence as a good engineering practice, it is not recommended to have such sharing of sensor among wo BPCS.



RE: Sharing of Transmitters for Different Control Loops

I don't see why you would need independent flow sensors here - a loss of flow indication will likely already shut down the pump, meaning flow control and minimum flow recycle control will not be needed.

RE: Sharing of Transmitters for Different Control Loops

I cannot understand what you are attempting to do. It seems that you want a common sensor, the signal from which is affecting 2 different control elements and either will affect the same process value? I expect each would fight the other.

Brad Waybright

The more you know, the more you know you don't know.

RE: Sharing of Transmitters for Different Control Loops

No harm done with the use of transmitters for more than one control loop, as long as the transmitter is not in any process safety function. Saves on CAPEX and OPEX maintenance.

RE: Sharing of Transmitters for Different Control Loops

Dear All,

thanks for your replies, considering the failure of the common shared transmitter can be latent (unrevealed) and if the transmitter is not provided with its own diagnostic coverage of the dangerous faults, then surely we would agree that sharing among two BPCS is not recommended.

Answering your Mr.Bard3 question, the same transmitter is used for sending a signal to minimum flow recycle valve and at the same time to pump's VFD. We agree that in case of low flow, the VFD controller would still dictate ramp up the speed while the controller towards minimum flow would dictate recycle operation. This ends up in having the two controller conflicting each other and mandating some kind of loop decoupling to override one another to accommodate the low flow scenario.

RE: Sharing of Transmitters for Different Control Loops

You seem to be seeking confirmation of the answer that you have already decided is correct. There is no inherent reason to not share the transmitter. Whether you should or not depends on many economic and safety factors, which we have no knowledge of.

RE: Sharing of Transmitters for Different Control Loops


We surely do NOT agree that sharing a transmitter reading among two different BPCS is inherently wrong or unsafe. The application needs to be considered based on the individual case. Certain requirements, such as adhering to a SIL-level or coupled-failure scenarios, may dictate more than one flow device and transmitter.

However, in your particular case, where you have a flow reading that governs both the pump speed and minimum recycle flow - potential control/interlock SIL rating issues aside - there is NOTHING inherently wrong with a shared transmitter.

RE: Sharing of Transmitters for Different Control Loops

If the calibrated transmitter range required to operate two control loops is wide and results in reduced sensitivity in process parameter readout for one or more of the control loops, then it may be better to use to 2 separate transmitters. This is the only reason I can see for dedicated transmitters.

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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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