CorbyLee

Hi,

I've found that the secret to getting accurate flow total integration from a flow rate input is to carry out integration addition using the raw 6400 - 32000 input via an interrupt controlled routine (I'vehad accurate results using 10ms interrupt).

Attachedare example subroutines for such an application. First subroutine is called on first scan to initialise the interrupt routine. The second is the interrupt subroutinewhere two totals are calculated. One is a overall flow total volume since system started, the other is a volume used to trigger a regeneration sequence after which it is reset to zero. There is also facility to overwrite the calculated overall flow total volume from attached HMI screen if the software calulated value gets out of sync with the flow instrument calulated total which can happen over extended periods of operation and also if the PLC has to be stopped.

Hopefully the networkcomments make the logic clear but please feel free to ask questions.

regards,
Corby

 Hai 

am new to S7-200 PLC. We have CPU 224AC/DC Rly and extension card EM231 AI4 channel. I have to make totaliser for the flow transmitter (4-20ma). 

I dont know how to scale the input to the require range (0-18000 l/h) and how to make totaliser for the same. Like this we have 8 transmitter do to.

Kindly can you guide me how to do.PLS

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Split from Flow totaliser block lader.

Helmut_13

Hi,

check:

1. Input filer (systemblock) for analog inputs and try if you can find settings which fits to your application.

2. Have a look to the Tips&Tricks for S7-200. There is a very old one how to claculate average.

3. Best is to stabalize the value from the sensor.

Regards

Hai

am new to S7-200 PLC. We have CPU 224AC/DC Rly and extension card EM231 AI4 channel. I have to make totaliser for the flow transmitter (4-20ma).

I dont know how to scale the input to the require range (0-18000 l/h) and how to make totaliser for the same. Like this we have 8 transmitter do to.

Kindly can you guide me how to do.PLS

Hello,

maybe idea, in my opinion read analog value of flow isn't precise therefore I see this olution only for show this value on HMI or other kind of display/PC. In case you need prepare Totalizer it need to be simply precise, I see here maybe use of pulse output from totalizer configured and mapped as flow (pulses) per time but also only for display. Simply making totaliser from flow isn't good idea in my opinion, no problem if only for display as momentary value to see what flow is now on flowmeter. Totaliser can be prepared for ex. with liters also via pulse output from totaliser configured as number of pulses per liter. Then you can have number of pulses in your memory and you can easy calculate how much liters you have flowed. Probably better will be you give better info what you really need to do, maybe also what medium is used here.

Update: look to post of CorbyLee in this topic, his PDF can be helpful to understand some principles (link to topic): Flow Totaliser Block (Topic)