Measuring flow with the help of a pulse flow meter (S7-1500)

Hello,

I currently have a problem that i'm trying to solve to quite sometime. I have a flowmeter that gives 77.5 pulses/liter/min. I'm trying to measure the pulses with a S7-1500 system that has a DI 32x24VDC HF Module. So i got the special counter inputs (channel 0 en channel 1). I have been reading this document "S71500_counting_measurement_function_manual" but it isn't helping me 

Some more technical information:

Cycle time is around 1 ms

And the max range of the flowmeter is 50 l/min so i can get maximum 65 pulses per second so once every 15~16 ms.

I was thinking of measuring the time between the pulses but i don't have a countermodule. Could you help me and push me into the right direction ?

Thank you in advance,

With friendly regards,

Remco 

Hi,

did you also have a look in the device manual of you module?

Please look here:

https://support.industry.siemens.com/cs/de/en/view/59192896

Regards,

Towome

Towome

Hi,

 

did you also have a look in the device manual of you module?

Please look here:

https://support.industry.siemens.com/cs/de/en/view/59192896

 

Regards,

Towome

 

 

 Hi,

Yes, i did. But it isn't helping me. 

Hello,

don't know if i will be helpfull to you, but your post show me some old times when I was working with this. Just only one idea if you count with this, when flow start, probably time between pulses will be much higer due start run. Same maybe at end of batch f.ex. So your counting with pulses per second is dirty. Sry this is only first my idea, maybe i will recall my some other ideas to help you, maybe this infos will be not helpfull.

Duris_I

Hello,

don't know if i will be helpfull to you, but your post show me some old times when I was working with this. Just only one idea if you count with this, when flow start, probably time between pulses will be much higer due start run. Same maybe at end of batch f.ex. So your counting with pulses per second is dirty. Sry this is only first my idea, maybe i will recall my some other ideas to help you, maybe this infos will be not helpfull.

 Hi Duris,

Yes, i understand what you are trying to say. This is also a little bit my concern. I have been thinking about maybe use interupts and measure the time between the interupts.So basicly I will measure the time between the pulses this way. Do you think this will be a better solution ?

With friendly regards,

Remco

Hello,

I don't have my relevant answer to you this time, but I saw very helpfull topic, maybe giving you some idea  :

Totalizer Block for 4 flow meters

Give pls response.

Edit: found another very helpfull info:

Why this doesn't work? S7-1200

Duris_I

Hello,

I don't have my relevant answer to you this time, but I saw very helpfull topic, maybe giving you some idea  :

Totalizer Block for 4 flow meters

Give pls response.

Edit: found another very helpfull info:

Why this doesn't work? S7-1200

 Hi Duris,

Yes, this gave me some inspiration. I fixed it the following: I used an hardware interrupt on the positive edge of my puls signal. In the interrupt i read the systemclock and stored it. And then compare it to the systemclock of my previous interrupt. Then take the difference and store my new systemclock value so it can be used for the next interrupt. You can find a screenshot in attachment.

I also measured the actual time with a scoop and the difference between the PLC value and the Scoopvalue is less than a ms.

Thank you very much for the help and inspiration !

With friendly regards,

Remco

Hello,

glad to help you, but give thank to that guys who give that ideas, roll-back posts, give stars them, not me.