Proportional control leads to automatic instability

The PID parameters are not properly adjusted; it would be helpful to have screenshots of the fluctuation curves, as this makes it easier to make judgments

Dear, first you need to determine the unit of your scale – whether there is a % sign. If there is a percent sign, then that represents the scale factor; increasing this scale factor will reduce fluctuations； If the unit does not have a %, reducing the proportion will decrease fluctuations.

Great post! Professionals are welcome to answer questions... Thank you!

The original poster’s question isn’t clear. When you say that “the flow control of the two materials is done through proportional regulation,” do you mean two separate flow control circuits, or rather the adjustment of the flow ratio between the two materials? There are various reasons why automatic mode cannot be used as a control loop. First, you can switch to manual mode to check whether the system is stable; if it is stable, it indicates that the PID parameters need to be adjusted properly, and re-tuning is required ； Otherwise, it is necessary to check whether all components of the circuit are functioning properly (on the assumption that the circuit is properly configured and the instruments are appropriately selected). This involves examining each measuring instrument, control valve, the various cards in the DCS cabinet, as well as the connecting components between them.

Floor 8 explains it very clearly. The configuration can be checked again; if the two materials do not come from a single source and their proportions need to be determined through calculations (which is the case in many proportion control scenarios), then check the data source address of the calculation module, as this is where problems tend to occur. Or the data address that requires temperature and pressure compensation.

From what the poster has described, it seems to refer to a ratio control system, right?