RSLogix 500 Flow Meter Totalizer Signet 2551

[bearsgone]

Yes, I actually use PID. Based on Signets panel we are running about 60gpm so that is not a problem

I will try raw

 

[sthompson]

Yes, I actually use PID. Based on Signets panel we are running about 60gpm so that is not a problem

I will try raw

If you change it to Raw/Proportional, you will have to add another SCP Instruction for your PID, so I would hold off on that. Is there somewhere in the PLC or on an HMI that you can monitor the Flow Rate, and make sure it agrees with the Display on the Flow Meter? I would also put in some Trap Logic to monitor the Flow Rate, and make sure it never exceeds 70 gpm.

Stu....

 

[bearsgone]

Now I am confused based on harryting formula I have:

F8:20*(1/60000)*S:35 + F8:38

F8:20 running running SCP flow, F8:38 grand total

I get two operands in sequence error

To answer sthompson:

We have signet 8900 which is connected to flow meter and I am reading off 8900 panel. Between PLC and 8900 I have a discrepancy of 2-3k gallons a day

 

[sthompson]

Now I am confused based on harryting formula I have:

F8:20*(1/60000)*S:35 + F8:38

F8:20 running running SCP flow, F8:38 grand total

I get two operands in sequence error

To answer sthompson:

We have signet 8900 which is connected to flow meter and I am reading off 8900 panel. Between PLC and 8900 I have a discrepancy of 2-3k gallons a day

I was inquiring about Flow Rate, not Flow Total.

Stu...

 

[bearsgone]

I am sorry, there is nothing else I can check the accuracy

 

[sthompson]

I am sorry, there is nothing else I can check the accuracy

Is there not a Flow Display on the 8900?

Stu.....

 

[harryting]

Now I am confused based on harryting formula I have:

F8:20*(1/60000)*S:35 + F8:38

F8:20 running running SCP flow, F8:38 grand total

I get two operands in sequence error

Huh... Seems ok when I plug it into RSLogix 500, be sure you use the right symbol for division in 500 it's not a slash but a "vertical bar", try paste this:

CPT F8:38 ( ( F8:30 | 60000.0 ) * S:35 ) + F8:38

 

[bearsgone]

Re harryting:
I tried:
CPT F8:38 ( ( F8:30 | 60000.0 ) * S:35 ) + F8:38

If I give F8:30 value of 1, in 1 minute I get 10. If F8:30 is in GPM should not I be getting 1 by the end of first minute?

Should 60000 be 600000?

 

[harryting]

My brain ain't functioning this early in the morning (PDT)... so I'm not getting it.

Say you have 1 Gallon/Minute, with S:35 = 20 ms (just pick a nuber out the air, keep in mind this number changes every scan but for our example, let's say it stays at 20ms)

In one minute, how many of the equation will it excute (1 minute = 60,000 ms)?

Answer: 3000 times in one minute (60000ms / 20ms)

Ok, now, in one scan, how much flow has passed?

Answer: 0.00033 Gallon

using our equation 1 gal/min * (min/60000 ms) * 20 ms

===> so in one minute 0.00033 will be added 3000 times

===> 1 gallon

 

[harryting]

Added to say, when doing any kind of equation like this, just keep the unit straight. if your unit in GPM (Gallon/minute) and 1 minute = 60,000 mS. You are basically coverting GPM to GPmS, therefore you divide GPM by 60,000 to get Gallon per Millisecond.

 

[MATT116]

This seems to be very accurate. I've used it on a couple of jobs with 8900

 

[bearsgone]

RE: harryting

I agree with your logic and attached what I have. Was going to mention that if I remove .0 from 600000 I get Error: Operand sizes do not match but with .0 everything works fine. Maybe that is where I get the difference between 60000 and 600000 but why would .0 make a difference?

RE: MATT116

Thanks, I will try it

 

[bearsgone]

MATT I tried your code and it looks like it added gallons every PLC scan not ever second cause for a flow of 1 g/m I get 150 gallons after 10 seconds?

 

[harryting]

Matt's code require the use of STI Function File, where you set a set interval for the ladder to excute. For Micrologic 1400, you have to go to Function File -> STI and fill in the correct parameters. You have to make sure the totalizer ladder have nothing but the totalizer logic as posted by Matt.

Not sure about the .0 deal, doesn't seem to be an issue in my version of 500. But it shouldn't hurt anything.

 

[MATT116]

As Harryting mentioned you need to setup the STI function to call the ladder with totalizing code in it.

1st Create a ladder with the totalizing code in it dont put any other code in the ladder.
2nd Dont call this ladder with a JSR from main ladder.
3rd Setup the STI to call the ladder every second.

Hope this helps