NI 9361 Pulse Counting to Display Mass flow rate in terms of kg/h

[Deepa_Krishnamurthy]

Hi everyone,

I am trying to Display the Mass flow rate in kg/hr using NI9361 and cDaQ 9185. The Signal is connected to PFI0 9 and 28 respectively.

The device specs are:

Output type: Pulse

Pulse width: 100ms

Pulse valuse: 1kg per Pulse

Range: 0 - 7500kg/h

Problem: The Previous and current values are mostly same. and difference between them is Zero. so the flowrate is also 0. But the device Displays it as 800kg/hr.

Please find the attached VI as jpg.

Please guide to get the correct values.

Thanks in advance

Best Regards,

Deepa

[GerdW]

Hi Deepa,

Problem: The Previous and current values are mostly same. and difference between them is Zero. so the flowrate is also 0.

That's no problem. It's a fact and it's your measurement value!

Pulse valuse: 1kg per Pulse… But the device Displays it as 800kg/hr.

At 800kg/h and 1kg/pulse you get 800kg/3600s*1pulse/1kg=0.222pulse/s. Simple math, eh?

So there will be 4s without pulse and one pulse in the 5th second…

Maybe you should increase the time per iteration?

Maybe you should apply some averaging to your measurement values?

Maybe you should measure the time between the pulses (for low flow rates)?

When using pulses to measure flowrates you ALWAYS need to decide between accuracy and measurement speed!

[Deepa_Krishnamurthy]

Thanks for your reply GerdW.

The Output of the flow meter is Passive: open collector, 30 V DC, 250 mA.

Am I measuring it right with NI 9361?

[GerdW]

Hi Deepa,

Am I measuring it right with NI 9361?

I don't know. How should I?

With an open collector you usually need a pullup resistor. I guess the manual of your sensor has a paragraph on this topic…

[Deepa_Krishnamurthy]

Promass 83I by E&H is the flow meter, from which i am trying to get the flow rate.

Its pin 24+ and 25- is the Passive Output terminal. In the Manual only the type of Output is mentioned.

Should I provide a voltage of (5-10V) to Pin 24+, inoder get the pulse Output?

[GerdW]

Hi Deepa,

why don't you read about open collector and pull-up resistor on Wikipedia?

You should learn the electronics basic before using them!

I'm pretty sure Endress&Hauser explain, how to use their devices, in several AppNotes or WhitePapers. Did you search for them?

Should I provide a voltage of (5-10V) to Pin 24+, inoder get the pulse Output?

Well, you might burn your device when doing so (or kill this open collector)…

No, you need a pull-up resistor!

[Deepa_Krishnamurthy]

Thanks a lot for the advice.

Will read about Basics. and try to get the result.

[Deepa_Krishnamurthy]

I could finally see the pulse on the oscilloscope. As the Output is Passive I provided a external supply voltage to the Output terminals of the flowmeter. I found this in one of their Manual.

Thanks for the help