Flow measurement for positive displacement pump

[Driga]

Hello all

I have this data acquisition task. The goal is to acquire the fluid flow. The system consists of peristaltic pump and flowmeter. What would be the steps for solving this task. I have no experience in this task, it is completely new for me. Should I know the spesification of each hardware (flowmeter,pump and DAQ instrument)? What should I need to know from each hardware?

For the pump, it said that it can be externall controlled through RS232, I do not know what this mean. Can it be controlled by labview?

Thanks a lot!

[zenthoef]

Knowing the specifications of all your hardware is important so that you can be certain your hardware can perform the task you you need done. What exactly is your task? To turn the pump on and then measure the flow? Does the system need to be in some state before you take the measurement? The specifics of what you are trying to do would be helpful.

Does your flowmeter have an RS232 (or other) interface? Or are you trying to get the data from the flowmeter with the DAQ? The flowmeters I have used have an interface that allows you to take a reading directly from the flowmeter. If you need to control your pump, or any other serial device, through LabVIEW, you can do so with NI VISA. See this: http://www.ni.com/pdf/manuals/370423a.pdf. Also, the VISA VIs are located in the Instrument I/O subpanel

I'd also recommend using a state machine as the appropriate architecture to solve your task. See this: http://zone.ni.com/devzone/cda/tut/p/id/3024

Hopefully this will help you get started!

[nathand]

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Driga wrote: 

For the pump, it said that it can be externall controlled through RS232, I do not know what this mean. Can it be controlled by labview?

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This means that it can be connected to your serial port, and you can control it using LabVIEW if you have documentation about what commands it expects to receive.

[johnsold]

A positive displacement pump produces the same flow for every revolution of the pump.  So to determine the flow all you need is the speed of the pump.  Check the pump specifications. If the speed control accuracy is as good as or better than the flow rate accuracy you need, then just knowing the command speed setting is probably sufficient.

Lynn 

[Driga]

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zenthoef wrote:

Knowing the specifications of all your hardware is important so that you can be certain your hardware can perform the task you you need done. What exactly is your task? To turn the pump on and then measure the flow? Does the system need to be in some state before you take the measurement? The specifics of what you are trying to do would be helpful.

Does your flowmeter have an RS232 (or other) interface? Or are you trying to get the data from the flowmeter with the DAQ? The flowmeters I have used have an interface that allows you to take a reading directly from the flowmeter. If you need to control your pump, or any other serial device, through LabVIEW, you can do so with NI VISA. See this: http://www.ni.com/pdf/manuals/370423a.pdf. Also, the VISA VIs are located in the Instrument I/O subpanel

I'd also recommend using a state machine as the appropriate architecture to solve your task. See this: http://zone.ni.com/devzone/cda/tut/p/id/3024

Hopefully this will help you get started!

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My task is to measure the flow. The characteristic of the pump compare to the graph which is given by the pump's manufacturer. I will check on the specification of each hardware tomorrow. 

Regarding your flow meter, is it stated in the technical data that the data can be directly acquired from the flow meter?

What do you mean by some state in your reply? Could you elaborate it?

I do not think that I need to control the pump, I just want to set the rotation speed remotely.  

[Driga]

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nathand wrote:

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Driga wrote: 

For the pump, it said that it can be externall controlled through RS232, I do not know what this mean. Can it be controlled by labview?

---

This means that it can be connected to your serial port, and you can control it using LabVIEW if you have documentation about what commands it expects to receive.

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I have read the pump's manual, I think I have seen such command. I will double check it tomorrow. Thanks! 

[Driga]

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johnsold wrote:

A positive displacement pump produces the same flow for every revolution of the pump.  So to determine the flow all you need is the speed of the pump.  Check the pump specifications. If the speed control accuracy is as good as or better than the flow rate accuracy you need, then just knowing the command speed setting is probably sufficient.

Lynn 

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the pump's manufacturer only give flow rate vs rpm for water. The pump is going to be used to convey a much viscous fluid, so the task is being given to me to check the flow rate characteristic of the pump. Thanks! 

[zenthoef]

By "some state" I was just wondering if you needed to measure the flow right when you start up or after some amount of time. You know, measuring start up state of your system vs. steady state, if you need it to get to some temp, etc... 

The flowmeters I am familar with do indicate that data can be directly aquired from them. 

[Driga]

 Ok guys, here are the known hardware for me:

1. Pump: a peristaltic pump, which can be controlled through RS232 connection. The data string format is available. It is listed as the command send to the pump, the command which the pump replies and the action. The connection is with RS232 port on one side and on the other side is 8 pins connector. How can I employ this to labview?

2. Flowmeter: 

    pulses: 319, frequency: 3.2 - 159. The output signal whether analog or digital still waiting for confirmation from the manufacturer.

3. National Instrument hardware:

   SCXI-1000

   SCXI-1300

What I am about to do actually trying to utilize an old test rig. So there are a lot of cables and the electrician was not available today. I am thinking of doing something first with labview to remotely controlled the pump, the later I will add this to the flow meter acquisition into labview. Will it work? 

Now, how can I start with the pump?

Thank you..

[nathand]

The problem with utilizing old test rigs is that they often have triggers or stop conditions that you won't see immediately, and when things don't work it can be hard to find out why.  For example, there might be an enable switch on your pump that's supposed to be connected to an emergency stop button or sensor and it won't work unless the switch is closed.  If you can't get it to work and you think you have everything right, try tracing the wires.

If there aren't any issues like that, then you should have very little trouble using LabVIEW to run the pump.  If you're lucky, the pump will use simple text commands, allowing you to use Hyperterminal to check that you can send commands and receive replies.  Then, take a look at LabVIEW's Basic Serial Write and Read example (you'll need to install NI-VISA if you don't already have it).  Make sure that you set up the serial port settings correctly and try sending commands to the pump, see if it responds. You should also search the NI site to see if someone has already written a LabVIEW driver for your pump, since that will make your work much easier.