Quantum : PID Cascade Loop

Hello All,
Pls refer the Figure
I am new modicon quantum also Concept v2.5
the client requirment is using a cascade loop
The requirment is like Operator Will enter Setpoint for Level controller PID 1
now i have maintain the Control Valve of the PID1 to 700GPM to 1500 GPM
which is Setpoint to Next PID2 i.e Flow Controoled PID
Pls Let me How to Scale the Analog Inputs in Modicon Quantum 11302
and How i can mainten the Control Output of PID1 from 700 GPM to 1500 GPM ?
if some one has Sample program in Modicon quantum (Concept v2.5 ) pls let me know
i have to do this assignment with 4 days of time
also how should handle analog float values

Thanks
Sandy

Concept has a function block that will take the input from your ACI module and prepare it correctly for PID functions.

Concept Help does not provide any application examples but it does a good job of flow charting the different PID functions.

You can find free knowledge base for Modicon products at: http://eclipse.modicon.com/ if you have a software subscription there is a more detailed knowledge base available when you sign in.

Thanks ,,, But how to do scaling to get 0-100%

Thanks Jim
Jim but iAm using 984 Ladder logic How i can do the scaling to get Analog vailue 0 -100 % is their any standard function aviable in concept v2.5 ?

Thanks
Sandy

Jim is the Modicon ace, but this is how I scale analog data in 984 logic. It may get you started on your solution.

I think this subject came up in a previous thread somewhere. We typically use the PCFL A-IN instruction for linear analog scaling.

For your application - to scale from 0-100% - just change the Lower & Upper Engineering Ranges to 0 and 100, respectively.

Also, you may need to load the 'A-IN Configuration Register' with a different number to suit your signal type:

0-20ma: #2816
4-20ma: #3072
0-10V: #2560
+-10V: #2048


-Trevor

By way of further explanation, I just wanted to give you an idea of one way to scale and manipulate data.

This was done in a Momentum. The input was 0-10 VDC and I was using a dropping resistor on a 4-20 mA signal, giving 2-10 VDC for my input.

The first step subtracts off the 20% offset, 6400.

The second step multiplies by the full scale value in engineering units for the transmitter. In my case I store the full scale in a register, 400334, so it can be changed if needed.

The third step divides by the data range, 25600. This comes from full range minus offset, or 32000-6400=25600.

I'm using double word math here to keep accuracy. The fourth step just moves the math result into a single word register fo use in the rest of the program and the HMI.

Again, this was just meant to get you started. I'm sure others that work with Modicon regularly have better ways.

If you are new to 984LL then be sure to watch the solve order of your functions. 984LL solves from top to bottom then from left to right.

This is not an issue in Tom's example as everything is on one line. It is a concern in Trevor's example, because he has the result of at least one function feeding into a different function.

Jim's correct with respect to my example: I'm feeding the PCFL block with the results of the ITOF conversions in the blocks on the left, then extracting the scaled result into another register.

This particular single-network approach is convenient to work with since whole computation happens during a single scan. I can scale all the (linear) analog inputs in a system using the *same* register range for the PCFL instruction, and simply need to change the destination register of the final FTOI instruction for each input. One network per analog input makes it easy to navigate later on.

The downside to using the same PCFL register for multiple computations means you won't be able to see intermediate results for any scaling network besides the last one scanned. However, I've never had a problem with this.

On a side note: If you wanted an upper engineering range > 32767, you'd want to consider moving the final FTOI instruction below the PCFL to prevent unintended 'signing' during the FTOI conversion in case of a PCFL error.



-Trevor