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Automatic Liquid Mixing & Dispensing using Feedback of Level & Flow Measurement
Need a solution for mixing a chemical with water at continuously variable concentration & volume.

Hello guys,

This is my first post here and I’m really looking forward to receiving some valuable inputs from you guys.

I have been trying to design an automatic fluid dispensing or make-up system for my CNC machine. A Level transmitter will be fitted to my sump, and I will use a refractometer to send concentration readings in 4-20 mA to a PLC.

Water & coolant concentrate have to be pre-mixed before being sent to the sump. Water shall be supplied to the dispensing system under gravity & coolant can be transferred from a drum/barrel placed on the ground.

Once everyday, a make-up cycle is required to be run which will use the inputs from the level transmitter & refractometer to decide the quantity of liquid to be topped up.

Since the water will be fed under gravity, can I use a flow control valve with a flow transmitter on that pipeline? And for the coolant concentrate, flow control valve with transmitter on the delivery end of the pump?

Also, I was wondering if I can use a Venturi Injector (Ejector) for mixing the liquids? Or maybe use PWM.

Feel free to let me know if the information given above is inadequate.


Since your flows and volumes are going to relatively small, I would
suggest displacement type flow transmitters or even small displacement or diastolic pumps to dispense the water and cutting fluid, and effectively "measure" it as well.

This will be simpler and much less expensive than flow transmitters and valves.

good luck