is it possible in Labview? Suggest me...

[shjukheter]

Here is again, I saw some mistake in befor posting..

1) I just started my work on yesterday. So, the pump is working good at 12V when there is no noise and even if you increase the voltage, still it is good but look like more strokes inside. I am not sure about this. I guess when increase the voltage, the number of strokes are fast.

[johnsold]

Thaks for the answers.  It is now much more clear what you are trying to do.

Question 5.  When they do the tests, is the pump away from other objects as shown in the image you posted? Or is it attached to some testing apparatus?

Based on those answers, I would recommend an accelerometer.  Install the accelerometer on the test fixture (bracket which holds the pump during testing). The exact postion of the accelerometer will depend on the direction of motion of the part which causes the noise.  The best place is likely to be in a straight line with that motion.  Read the accelerometer while manually adjusting the stroke.  The impact which occurs when the noise is created should be easy to detect in the output of the accelerometer.  Then repeat with the serial command to the pump and read the accelerometer again.  This can all be done in LabVIEW.

The accelerometer will pick up the impact or vibration from the pump but will not be very sensitive to other noises in the air.  I think it will work better than a microphone or other acoustic sensor.

Lynn

[shjukheter]

5) pump is always same, once they assemble all the parts and next adjust stroke manually then they do testing with liquid. That's it.

        OH! How you read the data from vibration sensor to Existing Serial between the pump. I am just doing with DAQmx to read the data from http://www.meas-spec.com/searchresults.aspx?search=4610-020-060 to labview and again take the stroke adjustment decision and fix it through SERIAL pump. I am not sure whether it will work or not. As you said with serial, how can I get the accelerometer data to labview from the existing serial communication with pump. In the meantime, I thought it will take more time rather than adjusting manuvally. Like this, Getting the data from sensor to labview via DAQmx and take the decision and need to check with all the strokes values from 0 to 255(let say 5 point increment always and check again for noisy vibrations and reading and checking with +5 increment..So on until it fixed). If it takes more time, then I fell to go for manuval adjustment. Do you have any suggestions?

[johnsold]

How much experience do you have with LabVIEW?  Do you understand state machines?

I would probably have the LV program set up to run as parallel loops.  One loop would have the DAQ read VIs to get data from the accelerometer.  Another loop would control the pump through the serial interface.  Possibly a third loop for an event structure to get input from the user, if needed. Pass the data between loops via queues.  Look at the examples and Design Patterns for Producer/Consumer and for state machines. 

Rather than starting the stroke at 0, determine the minimum value which has created the noise in the past and start with that.  Perhaps start slightly higher.  If the noise occurs at that setting, reduce the stroke by 5.  If not noise, then increase the stroke.  For example suppose that most pumps start making noise at stroke values of 150-200.  By starting at 160 you would rarely need more than two steps down or eight steps up to find the onset of the noise.  Starting at zero requires 30 steps to reach the minimum.  The actual values of course will depend on your production data.

Lynn

[shjukheter]

Yes, I understand well rather than design by self. Anyway, I would think later about labview first I am checking the vibration sensor with CRO, to see what level of voltage used to gave. I attached my sensor on pump which shows 20mv with zigzag analog signal look like below. I have no idea to proceed now.

[johnsold]

20 mV is small. You will need to amplify the signal before sending it to the DAQ device, unless the device has a built in amplifier to allow a full scale range of about +/-50 mV.

Set a threshold where you can separate background vibrations from the noise of the impacts, perhaps about 2 divisions on your image. If the signal is greater than the threshold, then you have the impact or noise and need to reduce your stroke.

Lynn

[shjukheter]

Hi,

       Can I connect two sensor to one DAQmx at a time. I mean I have vibration and pressure sensor and I want to connect both them to two channels in DAQ. I saw GND port also between each analog channel on DAQ. Whether I need to connect these GND pin always or not necessary.

[Ray.R]

You would want to shield the signal from picking up any interference signals.  So yes, Gnd is used..

I would also be concerned with ambient vibration with the pump.  You may want to look at that siognal and filter it out to get a cleaner profile from the accelerometer.

[shjukheter]

Hi, As you said to do amplification before connecting to DAQ. I don't see any noise on CRO but the output voltage is very low in mV. Some one told me that , we can amplify it in labview to certain level without doing any amplification outside. I looking for some suggestions. How can I go ahead now.

[johnsold]

You have not told us what DAQ device you have or its input voltage range(s).

Suppose you have a 16-bit A/D converter with a full scale input of +/-5 V. That means that a full scale signal would generate 65535 counts and a 20 mV signal would produce 131 counts.  You could multiply the 131 counts by 500 to get 65500 (which is mathematically the same as amplifying), but you would still have a resolution of one part in 131 rather than one part in 65000+.  If you amplify the signal (with a low noise amplifier) before digitizing, you can get the full resoution of the A/D converter.

Some DAQ devices (such as those designed to work with strain gauge bridges) have built in amplifiers.

So whether you need an amplifier or not depends on the DAQ device you are using or plan to purchase.

Lynn