×
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!
  • Students Click Here

*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

Jobs

Need help doing code for enclosed tank

Need help doing code for enclosed tank

Need help doing code for enclosed tank

(OP)
Hi Guys,

I need some help constructing a code using rslogix 5000 ver 7.02 to read the level of an enclosed tank.
I am trying to use two absolute differential pressure transmitters as the inputs.

The transmitters are mounted opposite each other. one on top and one at bottom.

I understand that i must subtract the the value of the top transmitter from the value of the bottom transmitter.

I also have to take into condideration that the tank is under vacuum.(read by top transmitter) but the vacuum is kept constant.
The pan is used for boiling syrup. so as time goes on the density of the liquid will increase.

I have very little experience with rslogix and I am having trouble getting this to work.

I used a subtract funtion and subtracted
Source A: Local:3:I.Ch1Data (lower transmitter)
from
Source B: Local:3:I.Ch1Data (upper transmitter)
to
Destination: A pre-defined tag in the controller tag section

I am getting a Zero (0) for the answer and this is incorrect.

I could use some help.
Thanks in advanced

CWYN

RE: Need help doing code for enclosed tank

This may be too simplistic, but aren't you subtracting the low from the upper when you should be subtracting the upper from the lower?

"Do not worry about your problems with mathematics, I assure you mine are far greater."   
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

RE: Need help doing code for enclosed tank

Source A and Source B are the same value.  Source B needs to come from another location.  Go online with RSLogix and open the Controller Tag page and look at the "monitor" screen.  Look at the values of the analog input card to determine the location of the data.

And the lower sensor should have a higher vaule than the upper sensor.  What is the density of the liquid and the distance between the sensors?

RE: Need help doing code for enclosed tank

Source A: Local:3:I.Ch1Data (lower transmitter)
from
Source B: Local:3:I.Ch1Data (upper transmitter)

If you notice your sourceA and sourceB are the same data ch1.  Of course your getting zero.  Take a deep breath and try again.  

Also be careful with taking raw data and doing a calculation.  Always buffer the data, test the buffer data for correct range of value.  Then perform your calculations.  That way you will not perform a bad correction to bad data received.

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