Production rate per hour from Flow

[Hubert12]

Hello PLCTALK members,

I am looking for the most effective way to calculate and store production rate per hour.

Case study:
I have an analogue flow sensor that is measuring flow of the gas produced by the plant.

My idea was to integrate sensors input and calculate the gas produced per hour, but I have no idea how I can make that in RSlogin5000, can you give me some tips?

Best regards,
Hubert

 

[Tom Jenkins]

Essentially use a timer to establish a short interval for making a calculation. Multiply the flow rate at that time by the interval, which will give you volume. Total the volumes for an hour.

See: http://en.wikipedia.org/wiki/Simpson's_rule for the theoretical basis.

 

[Martin Nielsen]

The flow sensor is analog, so I expect the signal between PLC and sensor to be analog as well? E.g. 4-20 mA or bus.
Do you have any digital option from the gas sensor?

Do you want to store the produced gas every clock hour?
E.g. the produced amount of gas in m3 from 13.00 to 14.00 etc.

 

[daba]

Essentially use a timer to establish a short interval for making a calculation. Multiply the flow rate at that time by the interval, which will give you volume. Total the volumes for an hour.

See: http://en.wikipedia.org/wiki/Simpson's_rule for the theoretical basis.

As an alternative to using a timer, place your calculation inside a periodic task. This will give you better timing accuracy, and will give a more accurate result. For the utmost timing accuracy, give that periodic task the highest priority (lowest number, i.e. 1).

 

[Hubert12]

Thank you for your valuable answers!

The flow sensor is analog, so I expect the signal between PLC and sensor to be analog as well? E.g. 4-20 mA or bus.
Do you have any digital option from the gas sensor?

Do you want to store the produced gas every clock hour?
E.g. the produced amount of gas in m3 from 13.00 to 14.00 etc.

Yes, it is 2x 4 - 20 mA analogue:
First connection is flow rate in m3/h
Second is metane fraction in 0 - 100%

I think there's no digital option.

Yes I'd like to store amount of gas produced every hour in the exact format as you wrote.

 

[lostcontrol]

The Logix5000 instruction set has a totaliser function.
Create a 25 element array. When the click hour changes, copy/move the totaliser output into the element if the array that represents you current hour & do a reset of the totaliser.

 

[Hubert12]

The Logix5000 instruction set has a totaliser function.
Create a 25 element array. When the click hour changes, copy/move the totaliser output into the element if the array that represents you current hour & do a reset of the totaliser.

Okay, I've managed to solve the problem.

The solution:
I created a totalizer with auto reset each 60 minutes, after the reset .OldTotal value is moved to Array[25] with FIFO block. Also added possibility to manually turncate Array[25] and reset totalizer from operational panel.

Thanks for all your tips!

 

[Hubert12]

Can I use the same principle for kWh input from power meter?

 

[Martin Nielsen]

kw on an analog signal: yes
kwh on a digital signal : no

most power meters have a digital output who gives a pulse for every kwh or other. then use a counter; simple code, cheaper and more precise.