Posted on Feb 6, 2014

There are three Controls to be Adjusted to make a Proportional Flow Controller Perform Properly. This method has to be practiced and experience gained from it can be used to get very good and stable Control of the Flow or Velocity of a Fluid. This is the Actual Flow Rate of the fluid in the flow sensor or its path. It is very important that the Fl

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ow Sensor is placed at a position in the fluid circuit in such a way to avoid cushions which may lead to oscillations around the Setpoint. The Flow rate zone in which the Output is 4. 1mA to 19. 9mA which in turn Drives the AC-Drive >> Motor from 0% to 100% is the proportional Band. It is Given in % e. g. 50% PB of 200 lph SP is 100 lph. Band 150 lph 250 lph eg : The Motor is at 100% Drive on` till 150 lph and off` above 250 lph. ` Between 150 to 250 is the PB. A little above 150 the Motor reduces power gradually till at 250 it turns off. When SP=PV the output is 12mA (ideal) here the motor runs at 50% of the total power. The Motor / Drive Combination must at 12mA Control signal give a flow Rate at which the system is used for most of the time this gives good stability. The max flow rate setting required by system must be achievable at 80% of Motor Time Axis Power this is to make allowance for load and line regulations. The Flow Circuit should have normal resistance to flow to reduce Oscillations. Here is a 4-20 mA In/Out Analog Mux with Cascade option. This is a simple circuit i designed to make a Automation System within a budget. This takes 4-20mA from many Transmitters and gives out just one 4-20 mA output. The Mux is done with a digital byte or word. This is a slow scanner as process is slow, that way many analog inputs can be multiplexed and sent into one analog input of a D/A. In near real time systems a faster mux...

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