help

[raoof]

hello

my self abdul ...i need help please help me out ...

i want to read current values with step  size of 0.1 voltage till 5 volt from laser diode driver(FL500) via USB 6009 ...so please ... can any one tell me the connection to read current values i.e on x-axis volatge and y-axis current as ouput.

and here i am attaching my programe which i try to read it but i was falied to do it...waiting for reply

[GerdW]

Hi raoof,

but i was falied to do it..

Where exactly did you fail?

- What is the difference in your calculation of "c" and "st", so you need to calc them both?

- Why do you use a While loop instead of a FOR loop?

- Why do you read 1000 samples for each voltage setting?

- What is your task definition? Your subVI is missing…

- How did you wire your current? The USB6009 is not capable of measuring current directly…

- Why do you use the DAQAssistent instead of plain DAQmx functions as you did for reading the AI channel?

[raoof]

hello Gerdw sir

1) i failed to get output of current verses voltage

2)c is variable and st is step here to stop my step when it reach to 5 v

3)for continous itteration ...as need to read volatge with step of 0.1 till 5 v

4)just i give 1000 samples to read but it can be change .

5)my task defination is to read current of laser diode driver via USB6009 . and here i was provided with dammy laser diode with 10 ohm resister...so i need to get my output current and volatge values in graph  with step of 0.1 till 5v as i am giving 5 volt from power supply..i  will attach my vi

6)accroding to my knowledge sir in DAQ assistant we can not define our respected values so i use DAMmx ...

sir please can you tell the connection

[CorinneDoppmann]

Hi raoof

Can you please attach the "my voltage 1.vi" that you are using as a SubVI?

Thank you,

CorinneD

[raoof]

hello i am attching my sub vi file please look it and give solution for it waitng for your positive reply

[CorinneDoppmann]

Hi raoof

I'm sorry, I do not really understand what you are trying to do in the newest version of "my voltage task.vi" that you posted.

The vi is currently doing two things:

The while loop with the DAQ Assistant will continuously read out the "Voltage" channel between 0V and 5V and plot the read values in the Waveform Chart.

The two while loops are completely independent to each other.

The upper while loop, where you calculate c and st will allways plot a sinusoidal.

I think the old version of "my voltage task.vi" was closer to what you were trying to do.

As far as I understand you want to create an IV plot where you sweep from 0V to 5V and read out the corresponding current values.

Could you please tell me, how you want to measure the current? Because the USB 6009 only has analog voltage inputs, so you somehow must convert your current measurement to a voltage measurement. 

In order to create the IV plot you only should have one while loop with three steps:

1. Write out a voltage value

2. Wait for your system to settle

3. Measure the corresponding current

You were doing these three steps in the old version of "my voltage task.vi"

I think your main problem is the third step: to measure the corresponding current.

To find out what the problem is, I would need more information on the "my voltage 1.vi" , which probably isn't doing what it should.

And you should probably convert the measured voltage to the current value somehow, depending, on how you measured the current in the first place.

The way you create the XY Graph after the while loop should be correct. 

Best regards

CorinneD

[raoof]

hello

i want to get VI (voltage and current) graph.. with step of 0.1 V using muti power supply of 5 V via usb 6009...plaese can any one help me out  with the connection ...

and please check my prorame which i a m attching here ...and also my experiment picture which i am working.

thanks

[GerdW]

Hi raoof,

using muti power supply of 5 V

What is "muti power supply"???

please check my prorame which i a m attching here

You only read a single AI channel.

You don't output any voltage values.

You use a single X value with 1000 y values for your graph.

You do reading the DAQmx channel in a loop, but the graph is made outside the loop.

You only use the values of the last iteration to create a plot.

[raoof]

hello

thanks sir for replying me soon

muti power supply is power supply where i am giving 5V to laser diode driver..

and sir i didnt get your programe please send me once....

can you show me in detail how to read current values...........waiting for reply

thanks#

[crossrulz]

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@raoof wrote:

and sir i didnt get your programe please send me once....

can you show me in detail how to read current values

---

He didn't send you a program.  He told you what you need to fix in yours.

The best way to read current is with a little Electrical Engineering inginuity.  Ohm's law states that the voltage drop across a resistor is V = I*R.  So to measure current, you can measure the voltage drop across a resistor.  I = V/R.  They make really small resistors specifically for this purpose.  You should use a differential measurement when doing this.