PLC Totalizer and Storing each Value

[drbitboy]

The timebase configuration for the TOT instruction mentions the following values: 0 - seconds, 1 - minutes, 2 - hours... where did you get that 3 from??

This link: https://literature.rockwellautomati...re/documents/rm/1756-rm006_-en-p.pdf#page=131

 

[MaxK]

4-20 mA open signal?

And why does the OP totalizing up the data from the disabled sensor?
Just kidding.

I'm 99% sure the issue is scaling (values, times). I.e. until there is confidence / understanding that the scaling is correct (volume / time -> mA -> bits (ADC) -> floating point value), further reasoning is of little use.

 

[cardosocea]

And why does the OP totalizing up the data from the disabled sensor?

I'm not sure if the low flow cut off works for the negative values if set different than zero, but it's worth looking into it.

This link: https://literature.rockwellautomati...re/documents/rm/1756-rm006_-en-p.pdf#page=131

Interesting, I looked at the instruction itself. Though the timebase is for the input unit, so 3 isn't correct.

 

[OkiePC]

Hey Guys I'll try to answer all the questions
I appreciate the help and feedback

1. The PLC is a Compact Logix L32E
2. The Flow meter is a Coriolis 5700 meter
3. The units are in bbls/min coming into the PLC
4. I have another totalizer setup from an previous flow meter installed and it totalizes fine. I thought it might be the settings in the TOT, but I used the same exact settings. the previous flow meter units is in gal/min though.
5. I have the "Timebase" setting to 3 in the TOT settings. See pics
6. The 5700 meter does have its own totalizer built in and it is correct. I assume its a setting in the PLC TOT.

thanks for helping

Then

can you use a different protocol (modbus ec) to read the instrument?

This is the ideal way to go, otherwise you are guaranteed to end up as the man with two watches.
Why build another watch when you can just ask the guy you trust standing right next to you?

With analog conversion involved, the totalizers will never exactly match, although they should be very close if you do it right. How close is good enough might depend on who's looking in what industry. Most flowmeters have a low flow cutoff as does the add-on instruction so those values need to match along with the usual things like exacting precision in transmitter and receiver calibration.

The 2nd best option is pulse counting which can suffer from an offset error if something is powered off or reset to a mismatched starting point, but should not accumulate a growing error.

 

[cardosocea]

Picking up on OkiePC, another option may be to use HART (if you have the IO for it) to read the totaliser and reset it. Rockwell has a document outlining how to do this with CIP messaging.