PID - 2 input

Hello

what PID block is prefered?

Im need controll water temperature but i have two inputs pipe. First hot water and second cold water.

Do you have some idea what libery from s300 is best? Or how to do it?

Have nice day all :) Marek

Hello!

I'm assuming you want to control the temperature with a S7-300 CPU. Take a look at the attached .pdf. Might help you.

Regards.

Hello Marek,

As af as i know, a PID can have just 1 input, however, there are other posibilities to ad more inputs but you need more PID functions. You can use individual control for each part (like double PID formats), or use Cascade PID that allow you control the inputs in 1 process.

You can check these posts that is releated of what you need i think xD

Control With 2 Inputs (you will need a s7-1x00 xD=

Cascade PID

I hope this can help you.

Regards,

Javier

Hello

For Temperature Control the the TCONT Std Temp PID library  ( FB 58 , FB 59 ) can be used.

However for many Temp control applications, Std PID Temp control ( FB 41-43 ) also works fine.

Both libraries are available in SIMATIC Manager:

Open->Library->Standard Library->PID Control Library

The actual usage will depend on the control requirement.

How many Temp Sensors do you have ?

How many control valves do you have ?

Do the control valves require Continuous (mA) signal or  Pulse commands ?

Hope this helps

Cheers
Navnag  
 

Marek cz

Hello

what PID block is prefered?

Im need controll water temperature but i have two inputs pipe. First hot water and second cold water.

Do you have some idea what libery from s300 is best? Or how to do it?

Have nice day all :) Marek

I prefer FB41.

But what ever FB you use,

in your case, watch it:

Use LMN (manipulated variable) Limits +/- 100%

If LMN > 0% you need hot water.

If LMN < 0% you Need cold water.

So you need a compare function to select hot / cold pipe depending from PID output!

Marek cz

Im need controll water temperature but i have two inputs pipe. First hot water and second cold water.

 Hey Marek, i just realise sth....

You say you need 2 inputs, but in you application you have is 2 outputs...

Let me understand, you say you need to control water temp, but you never say you are use 1 or 2 temp sensors... so i asume you are using just 1 (like controlling a tank temp). Following this, while you control the temperature, you will control 2 valves (assuming they allow the water flow to the tank).

One Valve opens when water is too hot, so send cold water.

The other one opens when water is too cold. Once you get the SP temp, it close bot valves (it might be servo valves or just on/off valves).

So you can lead the 2 valves with just 1 PID and some conditios or instructions.

If i'm right, we can help you in a better way. if I'm wrong, plz, detail better what you want to do.

Regards,

Javier 

Marek cz

Hello

what PID block is prefered?

Im need controll water temperature but i have two inputs pipe. First hot water and second cold water.

Do you have some idea what libery from s300 is best? Or how to do it?

Have nice day all :) Marek

 MrMr.Mrek cz

Your question (query) is very interesting 

But I think it's not proper explain ,so please explain proper,

If you going to controlle with use of control valve you should use FB 41

Dear Marek,

Please give detail properly.

Like if you have two pipe then how many valve you have means in some system only one control valve used like split control and some time two control valve also used each for pipe.

After finding this you can use simple PID block for single valve simply and cascade mode for two control valve.

but you can do it using simple PID block.

I think it may usefull for you.

Marek cz

Hello

what PID block is prefered?

Im need controll water temperature but i have two inputs pipe. First hot water and second cold water.

Do you have some idea what libery from s300 is best? Or how to do it?

Have nice day all :) Marek

 Dear Mark,

You have two pipes so i guess you have two flow control valve for that.

So You need to use ratio control...! For that you need to use two PID i.e std pid Cont_c blocks

and follow theory of ration control!

Thanks & Regards,

Dhaval ABotiyawala

Dhaval Abotiyawala

 ..

So You need to use ratio control...!

...