How do I replace the Process simulator with a 4-20ma input from a DAQ and to give a 5V Output to DAQ also to switch on Pump

[Brendanbyron]

Guys,

I am building a Level interface and I have a Labview example that I want to use. The only thing I need done is to change the Process Simulator with a DAQ. I want to take in 4-20mA input and use this as my process variable. Then using PID control I want to give a 5VDC output to an Analogue Output in a DAQ also.

Im very lost in getting this working.

I appreciate any help guys.

regards

Brendan

[Kurt_NISalesEngineer]

Hi Brendan,

Thanks for posting your query on the National Instruments forums.

Can you tell me more about your setup. what data acquistion DAQ card do you have in your computer? This Forum was started a while back - can you tell me the current status of the project please. Are you new to LabVIEW? If so have you considered pursuing a LV course?

Kind Regards,

Kurt

[Brendanbyron]

I am using a DAQ USD 6008.

I am still stuck on this part. My project is due in 2 weeks, I am trying to resolve this problem .

Do I set up an array. The Output is coming from the PID toolkit and I want it to switch on a single phase pump. I have the pump switching alright manually.

Can you lend any insight.

regards

Brendan

[JonBowers]

Hi Brendan,

If you want to measure a 4-20mA signal with the USB-6008 you will have to use a resistor and measure the voltage across it. With the DAQ Assistant  you can set this type of measurement up fairly easily.  If you place down the Assistant then set it up to acquire a current input. You can then specify the value of the shunt resistor you are using and the DAQmx driver will do the voltage-current conversion for you. You will need to set up the Assistant so that it acquires one sample on demand. The DAQ Assistant will return the sample in the dynamic data type, which you should be able to wire into your PID control.

As for the output you just need to set up another DAQ assistant to generate one sample on demand and pass it the output value.

I hope this helps

Regards

Jon B
Applications Engineer
NI UK & Ireland

[joooh]

Hi!

I'm not sure if this topic is still active....

Anyway, I kind of have a similar problem by using the "tank level" example. I know how to get the data from the DAQ. But how/where do I connect the DAQ-Icon with the PID-control? I don't really understand where the process variable is brought into the control...

I would be very happy about help!