labview temp measurement program using daq 6008 and lm335 temp sensor

[razvan1515]

Hi, I'm new around here. I'm a student, and I need a Labview program for temperature measurement, using a NI USB daq 6008 and 8 temperature sensors - LM 335.

I never worked in labview, I have the 8.0 version.

Can anyone help me with an example of program? Even for a single sensor.

[johnsold]

First, as a student you will learn more if you do things for yourself, so generally participants on this Forum will not provide you with complete solutions.

A good place to start learning LabVIEW (LV) is with the online tutorials.  They cover the basics.  Search for Getting Started with LabVIEW.

When you are ready to start putting together your temperature measuring system, define the performance requirements.  In addition to the information you provided you need to know temperature range, desired accuracy and resolution, measurement time intervals, how the data will be displayed, saved or used, and perhaps other things.

That information will let you determine whether the sensor and DAQ device you have can meet the requirements. You can design the sensing circuits. (The LM335 by itself is not enough.  You also need at least a power source and a resistor.) Then you can design your program.  For the data acquisition part start with the examples which come with the DAQ drivers.  Some of those will likely be quite useful in helping you get started and may even do most of what you need.

When you get stuck, come back here with specific questions.  Tell us what you have tried and what did not work. Report any errors you have received.  Include your VI and some typical data.  We do not have your hardware, so we can help better when you include the data.

Lynn

[razvan1515]

well, i started with online tutorials, i've I studied online tutorials, I made ​​about 90% of the program, but now I know not a small problem to solve.

When taking data, there are some fairly large fluctuations in temperature, increases or decreases abruptly by 3-4 degrees Celsius.

Overall figure is ok, you can see differences, but the waveforms are sawtooth aspet.

My work studies the thermal regime of a coil in AC or DC. Temperature is measured by sensors 7 Lm335, two sensors are for inside the coil, 3 are in the middle coil, and two are on the outside of it.

I attached the program.

[johnsold]

The fluctuations may not be from your program.  I suspect that you have electromagnetic interference between the currents and voltages in your coil and the sensors.

Other notes: LabVIEW arrays are indexed starting at zero. Your program uses indexes 1 through 7. Are you getting the right data to the right indicator?

The Merge Signals node can be expanded for multiple inputs.  You merged all the signals once inside the loop.  No need to do it again outside; just wire the merged data out.

It could take almost one minute for your program to stop after the stop button is pressed.  You might want to look at other timing methods which do not require long delays.

You could use a Chart in place of the graph. Then you would not need the Collectors.  Set the output tunnels to indexing and you would get arrays of data to write to the file.

Lynn

[razvan1515]

The data is displayed correctly to each indicator, sensors are connected from input AI1, not from AI0. I tried to use waveform chart, I deleted collectors, but now the text file records only one value for signals.
I tried for the last 3 sensors to make the average property values​​, to get rid of those differences, but I think the result is not ok.

Can anyone who is documented to help me, I'm running out of time, in 10 days I have presentation of the diploma and I want the  program to go well.

[razvan1515]

And this is the program that works ok, but it uses collectors.

[johnsold]

In your version without collectors you do nothing to accumulate the data.  I had suggested using indexing tunnels to build arrays.  That eventually will have problems due to memory re-allocations for the arrays but at 2 points per minute you will be retired before you run out of memory.  The better approach is to pre-allocate memory for the largest array you might use and then Replace Array Subset inside the loop.

Look at this modification of your VI.  I do not have any DAQ equipment nor can I run DAQmx so I have not tested any of this.

Lynn