Chaman Ali

How i can make totalizer in delta PLC for calcualting Litters of liquid by flow meter

8 posts in this topic

Our task to know total water in tank by using flow meter 4-20MA .

so how can i use totalizer in delta plc

Share this post


Link to post
Share on other sites

Posted (edited)

So 20SX2 series has analog input channels which support input voltage and input current modes. You can find the connections of the inputs in the user manuals. Anyway I don't believe that the level of water in a tank should be measured by a flow meter. I think that a level meter should be used. Flow meter is used when a rate of water delivery is measured, not water level.

If you're using flow meter anyway to get the water level you should take a lot of things in mind - the initial level of the water, the moment and the average values of the meter diring the intake process, the time, the values of the flow (how many mA are equal to how many liters/s). In this variant there's a high percentage of miscalculation of the level due to the listed circumstances. 

Using a level meter instead of flow meter will provide correct results in real time measurements because it's values are reffered directly to the water level itself without the need to make intermediate calculations in order to get the level from the flow.

 

Is it necessary to use flow meter? Could you use level meter instead?

Edited by IvanBratanov

Share this post


Link to post
Share on other sites

Thank you so much for your guideness.

Actually Application needs flow meter. There are alot of water tanks are present on site. Operator just give a command on HMI water quantity like 500 litters , 300 litters etc for different tank. Water hose will be kept on require filling tanks for filling.

If possible, could you share your whatsapp number with me?

Share this post


Link to post
Share on other sites

Posted (edited)

If so then how familiar are you with the ladder programming? Do you have any expirience with the Delta PLCs? Because if you are a newbye in this area it will be very difficult for you to create a program. If you haven't had any previous expirience with the analog A/D and D/A then you should first start study it and when you are known enough then start creating programs. This is not an easy task.

 

I'm creating industrial projects with Delta IA products more than 20 years already and even for me there are sometimes minor difficulties.

 

 

Take a look at this video:

 

https://www.youtube.com/watch?v=LeiNCEBpceY

Edited by IvanBratanov

Share this post


Link to post
Share on other sites

Suppose your flow unit is M3/Hr.

Convert this value to M3/Sec. (This is easy)

Now accumulate this value at every second. (at the rising edge of per second bit, hope you know how to do so)

Call this function at every second ---- M3= (M3)+(M3/Sec)

And you know how to convert Mto liters, right ?:-D

 

(Disclaimer - This will not give the 100% right value because there is something called scan time in the PLC.)

 

Share this post


Link to post
Share on other sites
Quote

 

Suppose your flow unit is M3/Hr.

Convert this value to M3/Sec. (This is easy)

Now accumulate this value at every second. (at the rising edge of per second bit, hope you know how to do so)

Call this function at every second ---- M3= (M3)+(M3/Sec)

And you know how to convert Mto liters, right ?:-D

 

(Disclaimer - This will not give the 100% right value because there is something called scan time in the PLC.)

 

Before creating the calculations he has to set the inputs of the PLC for the right mode - 4-20mA, current mode. Next he should choose that the register of the A/D input being selected shows the current value only instead of an average by default. Next he has to convert the input A/D value to L/s. This is called a conversion ratio. For example if the full scale range of the input A/D value is 0-2000 for 4-20mA and the flow range of the flow meter is 0-100 L/s it means that the conversion ratio is 20. Without it it will be impossible to calculate the flow in L/s.

And only now can he start writing the program. The program should create a 1-second virtual gate. The 1-second time is the sampling frequency. It may be shorter or longer but the accuracy of the measurement will depend on that - lower sampling frquency, larger error.

On every pulse of the gate an internal register should take the current value of the flow meter. It should be converted to L/s and added to the intermediate sum. On each program scan the sum should be compared to the desired value and if it is equal or more, the process ends.

 

And that's just a rough description. Doing this in real is more than specific.

As you can see its not so easy to recreate that in a program. It will be the most easiest thing for me to write the program instead of the author of the topic but thats not the point. Thats why I asked him if he has some expirience with the A/D programming and with the ladder programming at all. As I said its not an easy task at all and without any basic knowledge it will not be achievable.

Edited by IvanBratanov

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now