Calculation of flow meter pulses

 Translation from the Russian text, using Googl Translate:

V.Khomenko2701

Hello, I need your help.

I recently took my first steps in PLC programming. I need your help in writing a program.

I have a pulse flowmeter, but I don't understand how to calculate the current flow value in m3/h and implement the summation function in m3

Below I will add the type and characteristics of the flow meter. Maybe someone has a spare moment to help me out

 Здравствуйте В. Хоменко!

You must first tell us which PLC you are using in this project. If you are using a LOGO!, which version and part number, this will help us answer your question.

A general solution for your situation would require a high-speed counter in your PLC, both harware and software. A LOGO! 230RC for example has 4 high-speed digital inputs, each counting up to 5 kHz (5000 pulses/sec).

Hope this helps,

Daniel Chartier

Hello V.Khomenko2701,

I wouldn't take that.You still have some soldering work to do or invest additionally in a converter. Unfortunately there is no type information and therefore no data sheet for the product. In order to program a calculation at all, you need more data about the output signal and the voltages don't match each other anyway.

Greetings Ella_68

(translated with Google)

Ella_68

about the output signal and the voltages don't match each other anyway.

It could work. Device is powered by 3...24V DC and output signal is square wav pulses.

Product page on manufacturer site.

Now, if I understand correctly, there are 7.5 pulses per "litres in minute". So maximum frequency is ca 3.8 Hz. (7.5 * 30L / 60s). Could be perfectly affordable for LOGO.

(by the way, original poster writes in Ukrainian language, not in Russian)

Hello WWEE,

Thanks for the link !

But with 24VDC you are already at the upper limit of tolerance. But I doubt how durable this will be in the long term. A sensor with an upper limit of 30VDC would be better. Experience has shown that these last much longer.

Greetings Ella_68 

(translated with Google)

Ella_68

But with 24VDC you are already at the upper limit of tolerance. But I doubt how durable this will be in the long term. A sensor with an upper limit of 30VDC would be better. Experience has shown that these last much longer.

Sure, a little tolerance margin is always good. I assume that weakest point here is some kond of physical impeller with magnet. Contactless open collector or transistor output circuit (hall sensor) probably works without glitches here and one can directly connect flow sensor output to LOGO 12/24 input without much overthinking.

I'm not in condition today where I can think of a program,  .

But thereshold trigger and counters will probably do the trick.

One of the threshold switches, which is actually intended for the fast inputs, and the analog threshold switches for the evaluation would be enough. Of course, the arithmetic instruction for a little algebra should not be missing.

Greetings Ella_68