flowmeter output pulses

[frank222]

hello

Friends need your help please, I need to keep constant the pressure of a liquid I am using a flowmeter with pulse output of 198.4 ppg, please an idea to use the PID function in high-speed input function would have to use the frequency counter, and then linearized, and an analog output to control a frequency for the pump, please if you could expand to have a clearer idea of the PID function, using a VISION 130.

THANKS FOR YOUR HELP

[Joe Tauser]

You need a pressure transducer. Hard to keep a constant pressure on a dynamic system if flow is your input, unless constant flow always equals constant pressure.

If you are indeed trying to control the flowrate, the HSC input has a parameter to report frequency as well as total counts. All the input and output scaling can be done in the PID block. Read the Help file on it - Index tab -> PID.

Joe T.

[frank222]

Thanks Joe for answering

if you want to maintain a constant flow, my question is the input pulse would have to bridge for the two entries because one of them is to tote and one for frequency, I also toltal total quantity of liquid in the PID PV would be my entry frequency input such 10Pulsed per second (10Hz), then I would have to maintain a fixed rate to a setpoint travez, please if you could help me with this that still do not understand well, the analog output for the inverter would have to linearize

Thanks

[Emil]

Hi Frank,

HSC (High Speed Counter) in Vision series OPLC has two independent funcitons - counting pulses and giving their frequency.

In Hardware Configuration of the project, after defining HSC function (in your case as "High Speed Counter") and setting a register to count pulses, when you click on the second line, you will be prompted to define a second register (MI) to get the frequency in Hz.

The next step will be to convert thye pulses to some Engineering Units, for example Gallons per Minute (GPM). The best way to do so is using the function Linearization (VisiLogic > Math Menu). There, in your case you need ot set X1=0 and X2=19840 pulses, while Y1=0 and Y2=100 Gallons per second.

The input X will be the register fro frequency you set in HWC and the output can be linked as PV (input) to your PID loop. According to expected range, you will need to define Min and Max limits for PV.

As CV, you need to set any MI and define the limits to 0 and 4095 (12 bit analog output). CV register can be linked direct in Hardware configuration (HWC) to analog output.

There are a several working examples in VisiLogic > Help menu > Examples > Version 860 > Project examples > PID folder. Please review them.

Please let me know if something still remains unclear and we can help you further.