mahmoud turky
Member
I have a flow meter its range up to 53m3/hour, and i want in my program when the flow meter be 400m3, stop the feeding pump.
Could anyone help me in that?
Could anyone help me in that?
Flow Meter
- Thread starter mahmoud turky
- Start date
Mickey
Lifetime Supporting Member
If your flow meter has a range up to 53 how does it measure up to 400? Or does it have the capability to measure up to 400 or greater?
What brand of PLC do you have? Most will have compare instructions to accomplish your task.
curlyandshemp
Lifetime Supporting Member
You will need a digital output that will give you 1 pulse per litre as an input to the PLC. If scan time is an issue , you can set up as 1 pulse = 2 litres .
set up in logic a button to start pump, use pulses from meter to count down from setpoint to 0 , then shut off pump.
You can subtract 1 or 2 litres from setpoint within the program to compensate for pump overshoot.
widelto
Member
First of all, what kind of flow meter are you using ??
Most of them have a totalizer, where you can see how many meters or units of measure have flown thru the meter. You save your totalizer before you start pumping and while pumpimg you substract your actual totalizer value minus data saved, this way you know how mnay meters while pump is on.
Roy Matson
Member
Integrator
It's simple, every few seconds add the flow rate to a variable "X"
e.g.
you are flowing at 50.1 m3/h,
your variable "X" goes 50.1,100.2,150.3,200.4,250.5,300.6..........
divide the variable by the number of additions per hour and put the result in Total "Y"
Now you have a nice simple intergrator with several decimal places.
I usually update my variable "X" every 6 seconds that way it's nice and easy to convert for units per minute by dividing by 10 or units per hour by dividing by 600.
Try it out with a dummy flow rate.
Roy
It's simple, every few seconds add the flow rate to a variable "X"
e.g.
you are flowing at 50.1 m3/h,
your variable "X" goes 50.1,100.2,150.3,200.4,250.5,300.6..........
divide the variable by the number of additions per hour and put the result in Total "Y"
Now you have a nice simple intergrator with several decimal places.
I usually update my variable "X" every 6 seconds that way it's nice and easy to convert for units per minute by dividing by 10 or units per hour by dividing by 600.
Try it out with a dummy flow rate.
Roy
bernie_carlton
Lifetime Supporting Member + Moderator
We still don't have an answer on the type of flowmeter. From the description it's probably analog but it just could be a pulse type with that as a limit on rate.
sthompson
Lifetime Supporting Member + Moderator
Use pulse output:
I'm with Curly on this one, Pulse Outputs are the most accurate. Integrators will work if the flow is fairly constant, but if it varies a lot, or stops altogether during the run, you will get erroneous results. As has been pointed out, better information on the Flow Meter, Analog Card, and PLC type will help us help you.
Stu....
I'm with Curly on this one, Pulse Outputs are the most accurate. Integrators will work if the flow is fairly constant, but if it varies a lot, or stops altogether during the run, you will get erroneous results. As has been pointed out, better information on the Flow Meter, Analog Card, and PLC type will help us help you.
Stu....
mahmoud turky
Member
OP
The flow meter doesn't give me a digital pulse, only what i have that it's range from 0m3/h to 60m3/h and i want when the water in the tank reach 400m3 stop the pump that feeds it.
That's exactly my project.
That's exactly my project.
It sounds like you need to totalize based on your flow reading over a period of time.
Roy mentioned one method of doing it above. I think that 6 seconds might be too long of a sample rate. I figure that the shorter the duration between samples, the better. I usually totalize by multiplying flow rate analog input by the PLC scan time (scaled to the time units of the flow meter) to get the volume pumped during that duration. I then and add it to a register each scan. When the register value approaches your target, stop the pump.
Roy mentioned one method of doing it above. I think that 6 seconds might be too long of a sample rate. I figure that the shorter the duration between samples, the better. I usually totalize by multiplying flow rate analog input by the PLC scan time (scaled to the time units of the flow meter) to get the volume pumped during that duration. I then and add it to a register each scan. When the register value approaches your target, stop the pump.
Mickey
Lifetime Supporting Member
Every Second:
(Instantaneous Flow/3600) + Accumulated Flow = Accumulated Flow
Compare Accumulated Flow:
If Accumulated Flow => 400 stop pump
You must decide when to reset the accumulated flow.
mahmoud turky
Member
OP
Mickey i exactly did what you say and it's a good solution, but i have another problem wanna ask you about it, when PLC stops Accumulated Flow returns to 0.
Is there a way to save it if PLC be stop?
Thanks
lakesidebc
Member
Use a "retentive" memory area
Depending on your PLC, there are lots of places to store the results of your calculations. The non-retentive areas like CIO 200 in Omron, or MW 200 in Siemens (for examples), will go to zero when the PLC stops. You should be using a "retentive" memory area like DM 200 in Omron, or VW 200 in Siemens (for examples).
What PLC are you using, and what address did you use for your calculation?
Depending on your PLC, there are lots of places to store the results of your calculations. The non-retentive areas like CIO 200 in Omron, or MW 200 in Siemens (for examples), will go to zero when the PLC stops. You should be using a "retentive" memory area like DM 200 in Omron, or VW 200 in Siemens (for examples).
What PLC are you using, and what address did you use for your calculation?
mahmoud turky
Member
OP
I'm using S7-300 from siemens and i'm using DataBlock to save the result of addition
jingo
Member
just to clarify in this statement (highlighted),,,"
The flow meter doesn't give me a digital pulse, only what i have that it's range from 0m3/h to 60m3/h and i want when the water in the tank reach 400m3 stop the pump that feeds it.
That's exactly my project. ,,,,just a clarification, are you talking about the VOLUME that filled inside the tank?
and also, like mickey's question,If your flow meter has a range up to 53 how does it measure up to 400? Or does it have the capability to measure up to 400 or greater?
please clarify...sorry for re-asking..
tnx,,
The flow meter doesn't give me a digital pulse, only what i have that it's range from 0m3/h to 60m3/h and i want when the water in the tank reach 400m3 stop the pump that feeds it.
That's exactly my project. ,,,,just a clarification, are you talking about the VOLUME that filled inside the tank?
and also, like mickey's question,If your flow meter has a range up to 53 how does it measure up to 400? Or does it have the capability to measure up to 400 or greater?
please clarify...sorry for re-asking..
tnx,,
Last edited:
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