Industrial Controls

Thread Starter


Joined Jul 4, 2008
I just started industrial controls class. So far it is very interesting. Except I am not the best at drawing this problem up but I think the attachment is pretty close to the question. thanks for any help or ideas. it would be greatly appreciated.

1. A certain process has two tanks. Tank A has temperature control loop with a steam jacket. Tank B has hot water inlet from the Tank A and cold water inlet from the top. The following assumptions can be made regarding this process :

1. The temperature of tank B is controlled only by the amount of hot water from tank A.
2. The level in tnak B is controlled only by its cold water inlet.

Draw a control diagram showing:

(a) control temperature at the outlet of tank B
(b) control level of tank A
(c) control level of tank B

I think I need to draw something like the attachment except with two tanks labeled A and B. i know I need to study it more but a little help in the right direction would be good also.



Joined Jul 23, 2009
Hi Bigcountry,

Have a look at the attached file in Adobe pdf format. The file has a diagram for the 2-tank system you described. You probably need to adjust it a bit to the format that your instructor expects, but the attached diagram is fairly complete. For example, in the drawing you attached from a book, they used a summing amp with 2 inputs that were both positive in the amp. Therefore, they had to make one of the inputs negative by making the voltage source that feeds the tank float potentiometer negative. This would almost never be done in practice for the main reason that the summing amps are almost always going to be op-amps that have one positive input and one negative input. Therefore, both sources that feed the op-amp inputs can (and must be) both positive so that they get subtracted by the op-amp. I hope that makes sense. But if your instructor wants you to use the book drawing you attached as the format for your homework, then you had better make the amp be a summer rather than a subtractor and also feed the top of the float pot from a negative source so that the amp in effect, winds up subtracting the two signals by adding a positive signal with a negative one.

Good luck,