Flow Totalizer with PLC

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Thread Starter

Pravin

Hi gents,

I have surf this site many times, found many useful informations. Thank u all and this site. Now i need some clarification with one of my issue.

We using schneider plc's for our pumping station and got a magflow meter for measuring discharge flow. Now the problem is, the pulse output for totalizing the flow from flow meter is given to a DI card. But pulse output given to that input LED indicating is always glowing. what it means is that instrument giving output pulse or not. Which side need to be checked,in instrument any pulse scale setting is ther or in plc scan time need to be adjusted.

schneider DI - 170 DI 35000
Flowmeter E&H - Promag 50W6H-****D

Looking forward for yur replies and suggestions

Thanks & regards
Pravin
 
R
Pravin,

Are you sure you have the mag meter set-up to give a pulse per unit volume. The standard is 2-1,000 Hz proportional to the flow rate. A standard DI module won't be able to read that high frequency. It's also possible that the output from the flow meter doesn't match the PLC input.

Regards
Roy
 
D

david mertens

Hi,

Check the frequency that is generated by the flow meter. most flow meters can easily have an output frequency of 1000Hz or more. most digital inputs can not handle this hence the sales pitch for high speed counter cards.

The only solution is to lower the frequency e.a. only 1 pulse per m3 in stead of 1 per liter. If that is not acceptable to your application, you will need to buy a high speed counter card or upgrade the instrument to a bus system connection like profibus PA or foundation fieldbus.
 
Many flow meter manufacturers that produce frequency outputs produce little inexpensive modules called "pulse dividers" or "pulse scalers" that will do this function. They were developed to allow people to use the contact closure input as a counter.

Walt Boyes
Editor in Chief
Control and Controlglobal.com
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If the pulse output is an open collector output you may need a pull-up resistor. Contact the service department of your vendors and read the manual...wiring diagrams for this sort of circuit are commonly in the manual.

Walt Boyes
Editor in Chief
Control and Controlglobal.com
www.controlglobal.com
Mailto:wboyes [at] putman.net
Read my blog SoundOFF!! At www.controlglobal.com/soundoff
 
The given Momentum Discrete Input Module Part Number of 170ADI35000 can not handle this type of fast input switching.

You are left with 2 practical solutions:

1) Install a 170AEC92000 High Speed Module

or

2) If you have spare Analogue Input Channel (4-20mA, etc.) in your system, you may procure a Pulse to Analogue Converter and deal with the matter as Analogue Value, not as a Pulse Value.
Taking into consideration the level of deterioration of accuracy caused by this convesion.

Regards,
Ashraf
 
Hi Gents,

Thank you all for yur replies, just exploring this site don't know whether this goes to all. Anyways gents coming to the subject.

Do any wring need to be checked in this case,coz PLC got loop power internal power) and magflow also got its own power supply. When i check the power removing the terminal near the pulse output its gives 24 V DC but once connected to that terminal don't measure anything. Does it means something? Also noticed the frequency it gives its around 250+ Hz only. Looking forward for yur replies
 
R

Randy Bryson

I agree with you Ashraf. If you look at the piece of the model number supplied, the meter comes with both a frequency output and an analog output with HART. If this guy has an extra analog input, assuming the cable distance isn't too long, he can land the analog output directly on the analog input card. I have used lots of Momentums in my time and find this to be quite easy. We don't use a lot of E+H flow meters. We typically use ABB, but the concept is the same. There is a nice totalizer function in the function block library for the momentum. It scans 1/s. I find totalizing this way accurate enough for water applications. If you need revenue type metering, use a Coriolis from E+H or Emerson (Micromotion).
 
Hi Ashraf,

Thanks for your information, but can u refer any document proof so that i can talk with my people to buy new card. I find Schneider quantum card - 140 DDI 353 00 works with that E&H flow meter. It will be highly helpful if provide any documents that momentum cannot support this E&H.

Looking forward for yur reply
 
Hii roy,

Thanks for your reply.yes i got two options in that flow meter - Pulse and Frequency. Can u explain what way pulse/frequency differ and effect in my plc card. Now the setting is in pulse.

Pulse value - 10 m3/p ; pulse width: 100ms is the inside setting. How can we measure from instrument side to conform its giving pulse output.

looking forward for your reply.

regards
Pravin
 
Pravin,
Sorry for the somewhat late reply.

1) Please do not confuse me.
Your initial question was about a MOMENTUM PLC .. and your latest reply is talking about a QUANTUM PLC. WHICH PLC do you have there? a MOMENTUM or a QUANTUM?

2) I did not mention in any part of my message that the MOMENTUM can not do the job. I was merely talking about the DI Module No. 170ADI35000 which you mentioned. I also suggested 2 solutions, one of them is to install a Fast Input Module No. 170AEC92000 (Counter Module).

3) As I answered earlier, this MOMENTUM DI Module which you have in hand can not handle "Fast Input Switching". The Minumum Input Switching Time (INPUT RESPONSE TIME) is around 3.3ms. Hence it can not sense the pulses coming from the Flowmeter. So, the MOMENTUM PLC you have can be used with a Fast Switching Input, providing that you use a High Speed Input Module. Not the conventional DI Module you have in hand.

4) I do not know what document proof you want me to provide. Everything is mentioned in the Data Sheets of the product. This is the proof. Please read it and you will understand what I am talking about.

5) Now regarding the Quantum DI Module No. 140DDI35300 which you mentioned:
If you have a QUANTUM PLC there and you want to use the 140DDI35300 DI Module, this DI Module has a response time of around 1ms. It can sense input switching or around 1kHz or abit less.
Yet again, it depends on what you really want to do. Do you want to count pulses within a certain range or you want to use it for frequency reading? It all depends on the type of logic you will programme the PLC with, and it also depends on your requirement.

6) Please let me emphasize that I am here not talking about connecting this DI Module to a specific device with a specific Brand Name (E&H or whatever it may be).

I am talking about Scientific Facts. Please do not get yourself confused between the 2 concepts.

Regards,
Ashraf
 
Hi Ashraf,
How you doing, I thank you and appreciate the effort you took to explain.

- Well,since our discussion is with respect to the context of earlier mentioned model number i didn't mention in the reply thread but even i was meaning the same momentum DI module 170ADI35000.

- Reason i mentioned quantum plc 140DDI35300 is in our plant we got both momentum and quantum plcs for different application. So that quantum DI module is working with the pulse device very well just for you information.

- And finally to all our surpise even the MOMENTUM DI module 170ADI35000 is working now. How - some setting parameters changed in E&H instrument. The pulse output option of E&H instrument got the following settings

Pulse Value - Factory setting - 100 m3/p when changed to 1 m3/p it worked. We started seeing pulse input in the DI module.May be for low flow application it suits?? can explain this???

Once again thank you and everyone for your replies.

Regards
Pravin Jayapaul
 
Pravin,

1) You are again mixing up the commercial aspects with the facts of science. The QUANTUM DI Module you mentioned is about 3 times "more sensitive" to input status change (from 0 to 1 and vice versa) than the MOMENTUM DI Module in question.

2) The QUANTUM DI Module has a response time of around 1ms, while the MOMENTUM DI Module which you also mentioned has a response time of around 3.3ms. So apparently, the latter will be much more less sensitive to the change of the status of the input.

3) I am really amazed by your statement "to your surprise, the MOMENTUM DI Module starting sensing the pulses from the flowmeter after having reduced the rate of pulse. You or anyone else there SHOULD NOT be "SURPRISED". Please read again the top portion of this message and my previous reply to you.

4) You are still linking between the generated pulse by your device and the flow rate. This should not be the case. The MOMENTUM sensed this change because the rate of occurence of pulse per second has been reduced.

This could have happened whether you have a flowmeter or any other device that has pulse output with certain magnitude.

5) I do not know and I am not questioning your background. But systems are integrated based on knowledge and understanding of the basic scientific facts and terms. Not based upon some device.

6) It is also worth mentioning that reducing the pulse rate, as in your case, will also affect the accuracy of reading. Industrial Systems are built for high accuracy, otherwise it is not economically worth it to invest in expensive equipment and devices, while using it to much less of its potential capability than what it can really deliver.

This is like hiring a whole bus to transfer 2 passengers from point A to point B, while you can do the same thing, more efficiently and more economically, by using a small car instead.

7) Anyway, if you are happy with the way your system is running, then I have no further comments.

The only thing you should know that, in the case of your flowmeter, that if the flow will increase beyond the capability of your system to sense the change of the status of input, then your present setup will not be able to sense or handle the flowrate.

This is what High Speed (Counter) Modules are made and are used for.

Regards,
Ashraf
 
J
> 2) The QUANTUM DI Module has a response time of around 1ms, while the MOMENTUM
> DI Module which you also mentioned has a response time of around 3.3ms. So
> apparently, the latter will be much more less sensitive to the change of the
> status of the input.

According to the manufacturer data on the 140DDI35300, the response time is 1000ms max. Not 1ms. (Refer to the Quantum automation platform manual, section 2, page 18.)

> 3) I am really amazed by your statement "to your surprise, the MOMENTUM DI
> Module starting sensing the pulses from the flowmeter after having reduced the
> rate of pulse. You or anyone else there SHOULD NOT be "SURPRISED". Please read
> again the top portion of this message and my previous reply to you.

Why are you amazed?
He stated that he increased the resolution from 100m3/pulse to 1m3/pulse. An action that would increase the pulse rate by a factor of 100. Given the assumption the card was too slow to see a pulse every 100m3, why would anyone expect to see a reading when increasing the pulse rate?

> 4) You are still linking between the generated pulse by your device and the
> flow rate. This should not be the case. The MOMENTUM sensed this change because
> the rate of occurrence of pulse per second has been reduced.

His device is configured to give a pulse per volume. He is correct in linking between flow rate and pulses. He is interested in the flow rate for his process.

As stated above, the pulse rate has increased given the volume per pulse has decreased.

> This could have happened whether you have a flowmeter or any other device
> that has pulse output with certain magnitude.

He has a flow meter. What is your point?
The magnitude of the pulse output will most likely not have changed. The frequency of pulses has.

> 5) I do not know and I am not questioning your background. But systems
> are integrated based on knowledge and understanding of the basic scientific
> facts and terms. Not based upon some device.

The characteristics of a device within a system is something that has to be taken into consideration. Unless of course you are producing a theoretical system with no plans of ever putting it to use in the real world.

> 6) It is also worth mentioning that reducing the pulse rate, as in your
> case, will also affect the accuracy of reading. Industrial Systems are built
> for high accuracy, otherwise it is not economically worth it to invest in
> expensive equipment and devices, while using it to much less of its potential
> capability than what it can really deliver.

Again, he has not reduced the pulse rate. He has reduced the volume at which a pulse is produced. Increasing both the pulse rate at a given flow, and the measurement resolution.

Fora are far more useful if the people answering actually read and understand the problems rather than responding to the originator as if he were an idiot and spouting useless drivel in a patronising and arrogant manner.

I realise the thread is long dead, but having stumbled across this thread while searching for information on the 140DDI35300, there could be other people falling foul of Ashraf's misinformation and "advice".

My advice, ignore this thread.
 
Hi,

I face same issue with ABB watermaster flow meter. can't find pulse in DCS, just a continuous green light without pulse being received by the transmitter.

Hope you can help me in finding how to measure the pulse.

will be great help.
Regards
Barde
 
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