XY-Graph TORQUE AND POWER IN FUCNTION OF ROTATE SPEED

Question

Dear,
I have  made a program in Labview for my endwork so i have now one problem ; i read data (torque,temperature,power,speed of an engine with an USB-6009 daq-kaart.) now i want to make a graph of the torque (koppel in dutch) in funtion of rotate speed and also power(vermogen in dutch).  i have used xy graph but  i get nothing  . What do i wrong can some one help me? I send the program also as attachement ; on the y i will torque(=koppel) and x i will rotate speed (toerental)  
thank you
Attachments:
Eindwerk_data.vi ‏346 KB

Answer 1

Hey Drayton,
Please have a look at the attached VI.  
Left
of the While Loop I created a 2 dimensional array.  Column zero is
representing the RPM, column 1 the Torque (koppel) and column 2 is the
Power (vermogen).
Then I am simulating the measured data of RMP,
Torque and Power.  As I would like to limit the number of elements in
the array, I used the "Remainder and Quotient" function to round to a
nearest lower multiple of 20.  This means you will have steps of 20 RPM
in your graph.  The lenght of the array is in the case: 4000 RMP max /
20 = 200 elements.  Of course you can change this but then also your
array size will become larger (more processor time needed to analyze).
Next
step is to get the index number in the existing array which equals the
current measured RPM.    This index is needed to replace the
corresponding torque and power values in the array.
If the newest
torque or power value is greater than the already available value for
the corresponding RPM,  then this value will overwrite the existing
value. If not, then the existing torque and power value will be kept.  
Finally I will extract the complete columns of the array for RPM, torque and power to apply them to the XY graph.
You can almost copy/paste this into your VI.
As
your data is coming from Express VI, the wires contain waveform data
which also inclused timestamp information.  As you cannot use waveform
data with arrays and actually don't need it, you have to use the
function "From DDT". This is also an express VI to convert the Dynamic
Data Type from the Express VI into a scalar datatype.  You can show to
analyze only one point at a time of by using an array.
I have also seen that you have place additional numeric indicators on your front panel beside the meters.
This is great. You only used an additional object to do so causing also an additional terminal appearing on your block diagram.
Actually,
the numeric front panel objects have already an numeric indicator
related to it.  This way no additional block diagram terminal will show
up.
You only need to enable it.
Right click on the object to open
the shortcut menu ---> Visible Items --> Numeric Display.  There
is your numeric indicator directly related to the object.
If you do this for all you front panel objects, your block diagram will look much nicer and easier to read.
Best regards,
Joeri
National Instruments
Applications Engineering
http://www.ni.com/ask
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Attachments:
Arrays.vi ‏18 KB