using 1746-NI16I

[OkiePC]

Once online, I don't think you can apply changes.

I was wrong about that. You can make changes while online and apply them. I am not sure if this still works when you manually insert the rung or only when you let the software do it for you.

 

[jkCBWPnet]

I did not design the program. If it is wrong then allen bradley is wrong. It is copied [almost] directly from the example given in the user guide on pages 97,98 (see my first post for more info) I had searched around at the time (last week) and there was mention of config bits or something for those 3. I think I understand what you are saying but maybe they will always be good and the initial check is done from the PROG - RUN step? idk

ok i get it. the whole ladder program loops but rung 0 will only be done at the reset as per that switch's function. makes sense. (I didn't know if there were seperate loop instructions. I do other types of coding where the code only loops if you tell it to, thats why I asked)

I ran the meter through it's span and datalogged it. It seems to range from 4044 to 20100 am I guessing those values are something close to micro amp values (analog signal of 4-20 mA)
It is set in engineering units atm.

 

[jkCBWPnet]

ok going with the book that is indeed what I should have expected for values. My HMI seems to not accept -300 as an offset for whatever reason. How do make the PLC scale it for me? The flow meter is 0-1200 cfh so:
scaled value = (input * 0.075) - 300
how do I configure the plc?

 

[Lancie1]

It is copied [almost] directly from the example given in the user guide on pages 97,98 (see my first post for more info) I had searched around at the time (last week) and there was mention of config bits or something for those 3.

First off, if you are going to use the examples in the manual, you have to complete ALL of the steps shown in order for it to work. I think you probably failed to notice the instructions on Page 7-21, and did not insert your Analog Input Module Configuration Word in N7:0. Without that, this procedure will not work, and will be worse than nothing at all.

The problem with the Allen Bradley manual is that they are not written for beginners, but are written to cause beginners to have to go to their local AB distributer for help, or even better, to sign up for one of the expensive AB training classes.

If you add a paralled branch on your Rung 000, and insert a MOV command between the FLL and the COP, and Move the value "-16192" to memory location N7:0, then your error-detecting procedure might have a chance to work.

Why do you need this fancy error-detection procedure anyway? Do you know that the analog module will work just fine without this fancy-pants procedure that only detects whether or not it is working? Normally, you will know if it is not working!

 

[Mickey]

With your card's data format configured for engineering units, this will give you

4.00ma = 4000 counts
20.00ma = 20000 counts.

See picture below for an example of how to get that raw data to your process engineering units.

 

[jkCBWPnet]

you are correct that I did not manually specify anything. I thought rslinx did whatever it had to do when I was in the configure page. Even though it works right now there could be problems. Could you help me make it right please.

 

[jkCBWPnet]

thanks mickey. should I append that above the move command then (rung 2)

did you mean for the output to be F8 ?

 

[Mickey]

thanks mickey. should I append that above the move command then (rung 2)

did you mean for the output to be F8 ?

Yes F8:0 is the scaled data 0.0-1200.0. ( I like floating point data). You can use an integer instead if you want.

The example I gave uses the cards input word directly ( my preferred method).

If you want to use the N7 words you have moved the input data to instead of the I:3.0 that will also work. Just replace I:3.0 with the N7 word in the SCP instruction.You can put the SCP instruction anywhere you want, if using the N7 word then after the move would be good.

 

[Lancie1]

I copied the program from the user book on pages 97-98 of the guide. (except my card is in slot 3 not 6)

Back to basics:

For the TEST_NITRO program that you posted, you only have two cards, in slots 1 and 2 and neither is a 1746-NI16I. You have your processor configured for a 2-slot rack, which does not have a Slot 3. You need to do a "configure" and make sure that the PLC knows what processor, rack, and slots that you REALLY are using, and that the card is installed in slot 3.

 

[jkCBWPnet]

what do I do with the value from F8 then? The N thing was not my idea (not sure what pros cons etc are of each way. I would have just looked at the input directly if I hadn't been directed to the N in the first place.)

I just need this to work
although...
self education gets things working, but occasionally picks up bad habits. I would rather avoid those from the start if I could.

 

[jkCBWPnet]

if we are getting to basics, maybe I should just remove the first 2 (unused) cards and start w/ ana in as card 1...

 

[jkCBWPnet]

just so we are up to date on my current rss...

 

[jkCBWPnet]

can the SCP be substituted for MOV with input = I:3.0 (current location) and output = N7:30 ?

 

[Mickey]

That will work.

What you do with F8:0 depends on your process. You can read it from a HMI to display
it. You can use compare instructions to create alarms or take some user action. Use it to control a process e.g PID control.

can the SCP be substituted for MOV with input = I:3.0 (current location) and output = N7:30 ?

Not sure what you are asking here, see my example picture.

 

[jkCBWPnet]

what will work? rss?

I mean instead of a MOV command taking I:3.0 and putting it at N7:30 a SCP command taking I:3.0 converting it, then putting it at N7:30

(honestly I don't know why he suggested to have the bridge point to N)