10/31/2008 4:32 PM | |
Posts: 1 Rating: (0) |
I hope someone can help me with this problem. This is the situation: A big washing-installation has a water-reservoir where soap is pumped into. The soap-flow cannot be adjusted, so it's just on/off (relay-output). The amount of soap in the watertank is measured by a device which gives an analog 4-20mA signal, based on the conductivity of the water. The installation has a S7-300 station with an OP73. The operator will enter a value between (for example) 0 and 10 which represents an certain amount of soap. The S7 station needs to control the soappump until the asked soap amount in the water is reached. (like a temperature control, but scaled for a soapamount). basically I have this signals: OP73: WORD (setpoint soap) measure conductivity: ANALOG 4-20mA relay output: on/off for pump The tank is quite big, so the system will have a certain lag What I've done for so far -communication between OP and station, limited the inputvalue from 0 to 10 and transferred to REAL -scale the analog signal from 0 to 10 and transferred to REAL I have little experience with PID systems, but as far as I can understand I will need FB 41 (cont_c) and FB 43 (pulsegen). Why is LMN used in FB41 and not PV for FB43..?... I don't understand how these two blocks work together, neither what startvalues I should use for the PID control. I have no idea how the system will react. Is there an easy way tofind these parameters? Is this the right way to solve this problem? Can someone help me along? you can find my program in the attachment AttachmentPht____1.zip (614 Downloads) |
Last edited by: Basil007 at: 10/31/2008 7:24 PM |
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