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Hi all,

I wanna make a total flow (cubic meter) totaliser. The analog flow rate meter is in cubic meters per hour. Any idea on how to make this totaliser to indicate how much flow (volume) been through for a certain time in PLC or Pro-face?

Thanks for help.

From,
newbie

Hello Newbie,

Acromag offers Ethernet Modbus TCP/IP slave remote i/o products that may help you.

Model 989EN-4016, 16ch DIO w/ 8 pulse count inputs to non-volatile memory. If your system provides pulse outputs (i.e. 1 pulse for every xx cubic meters), they can be counted and totalized to nv memory on the 989EN. The PLC or Proface unit may be able to poll the 989EN counters via Ethernet Modbus TCP/IP to determine the totalized flow (i.e. volume usage).

If you only have an analog signal(s) from your flow meter (i.e. 4-20mA) and need to integrate and totalize off of the analog signal, Acromag offers several multi-channel solutions as well. They are Models ES2161, ES2151, and other soon to be released low channel count products as well.

If you have any questions or would like information on these solutions, please email me at dlupo at acromag. com

Kind Regards,

I think you can go through some code to do this, add the flow rate when it comes one second.

Sure, it's easy. If once an hour you take the flow rate and add it to a register that's accumulating, e.g. if your flow rate is 5m3/h your accumulator will go 5, 10, 15, 20, 25, etc.

But that's not very good is it, so then you do it much more often. Take the flowrate and divide it by 3600 and do it once every second or divide by 360 and do it every 10 seconds. The trick is to get a good accurate time period, in some PLCs timers aren't accurate enough so use one of the special timers based it on the Time of Day clock or put the calculation in a timed routine.

Use floating point maths.

You may also want to include a low flow cutoff so that the accumulator stops when the mA signal is very close to zero in case your meter has a zero error or it could be interlocked to some other function that you know stops the flow completely.

Post your PLC Make and model, someone will give you a better answer. Some flowmeters also give out a pulse/unit. If you use the PLC to count the pulses that can be very accurate, however if you just have a 4-20mA signal use the former method.

Regards,
Roy

Hi all,

Hi, thanks for the replies. It is very helpful to me. I got the idea now and I think I m gonna take every 3 seconds flow to accumulate up. I am using Schneider-Electric TSX Micro 3722001 PLC and PL7 Pro v4.4 to program it. Too bad my flow meter is just 4-20mA signal. Very much appreciated if someone got the sample application.

From,
Newbie

I don't have access to your PLC but it's quite simple. Use a dummy value to start with to simulate the flow, divide it by 1200 then every 3 seconds using a transitional contact to power up an add block that takes the value of your accumulator register and add the result of the divide calculation placing the result back in the accumulator. You must use a transitional contact or a timed routine so the calculation is only done once Once you are satisfied that it's working correctly substitute your flowmeter signal for the dummy value. 6 seconds is a good time interval, 10 times a minute makes the math easier. Accumulator = Accumulator + (Flow/600)

Hope this helps.

Thanks man! I'm gonna try this later~ BTW, which register should I store the accumulated value? Word (16 bits) or Dword (32 bits)? Word enough, right? Thanks... TSXmicro3722.

From,
PLC newbie

Sorry I haven't used a Modicon in years, should use a double word I think if that's the format for Floating point math.
You want a memory location that saves on power failure.
I'm sure a Modicon guru can help

Roy

in my place they do this but by another additional device called "PULSAR". i don`t know its brand or the manufacturer since i didn't work in it yet or by another way no faults occurred in this part yet.

But let me tell you the criteria that it works with:

It takes the analog signal form the field and integrates it.
and by the way it works also the same way you want since i`m working in waste water treatment plant.

The "MAGFLOW" gives the analog signal to this device and for example if made the presetting for this device to give me one pulse for every 1 m^3 of water then it will integrate the signal that comes to it and for every total flow rate of this value it gives one pulse.

I know that the signal can be driven directly to the PLC analog module and do all this calculations on it and i don`t even yet know why the designers did it this way, but i wanted to tell you this idea, i though it may be useful.

Hello Yong,
If your water meter is turbine-based or single-jet-based (eg. Sensus, Neptune, Badger, Actaris, Elster-AMCO, Hersey,etc...), then an EtherMeter (by SCADAmetrics) can be connected to the meter register, and this device makes the totalization and flow rate data available in MODBUS format.

Your PLC can then poll the EtherMeter (using MODBUS) for the correct meter totalization and flow.

The EtherMeter reads the totalization directly from the meter register in an encoded format, so you won't lose your totalization after a power failure, etc.

Hope this helps!

Hi all,

Thanks for the replies. The informations are useful to me. But my client just don't allowed me to add an additional device into this application, thus I can only do this by using PLC.

But in the future, I may propose these additional devices to other clients. Thanks again.

From,
newbie