Spikes in logged data

[ChNy]

Hi!

I have a problem using a Kistler 8792A50 accelerometer and NI cDAQ-9172 with a 9233 module. When I plot the logged data I get vertical "spikes" in the plot. Data is also missing around the spikes. Can someone help? I will also add that I’m a beginner so everything is possible 😕

[johnsold]

Can you show us data with the actual problem?  The image you posted looks like some lines were drawn over a data trace via a graphics program.

What is the full scale range as you have set your hardware and software? What is the sampling rate? How are you logging the data? Do you have any idea what could be causing your spikes?

Lynn

[ChNy]

I’ve attached the data. For some reason the up loader won’t accept .lvm files so I renamed it to a .log file. Sorry about that.

I've tried several ways of importing the logged data in to matlab so I’m confident that the problem is not a part of the actual importing process.

I’m logging with a sampling rate of 19.2kHz. From the 9322 datasheet I’m guessing the actual sampling rate 16.667kHz. I’ve tried to setup the system according to the datasheets for the Kistler accelerometer and the 9233 module. Thank you for looking at this...

The data is logged from a swinging ruler for an easy fft analysis. I’m trying to learn and understanding the concepts.

Note: The data from the error picture is from the Z-axis in .lvm file.

[johnsold]

When I look carefully at your log data I see no sign of the spikes.  However, if your import process includes the blank line between data blocks, that could produce a jump in the data.

This is an excerpt from the file when read as text:

---

1.999880 -0.009471 -0.007884 -0.163235

1.999920 -0.002806 -0.001346 -0.161478

1.999960 0.004451 0.005757 -0.155967

Channels 3 Samples 25000 25000 25000

Date 2012/09/21 2012/09/21 2012/09/21

Time 15:26:05.625 15:26:05.625 15:26:05.625

Y_Unit_Label g g g

X_Dimension Time Time Time

X0 1.9999999999999998E+0 1.9999999999999998E+0 1.9999999999999998E+0

Delta_X 4.000000E-5 4.000000E-5 4.000000E-5

***End_of_Header***

X_Value X Y Z Comment

2.000000 0.010570 0.011051 -0.151092

2.000040 0.012431 0.013021 -0.142521

2.000080 0.015900 0.017220 -0.130475

---

As you can see the values in the first column increase by 0.000040 in each row, including across the header separating the two segments.

Graphing the data from each segment separately shows no spikes.

Lynn

[ChNy]

Oh, I see. That’s the reason! But why is this happening every 2sec? Can I change something in the program to remove this?

Thank you!

[johnsold]

That probably has something to do with the settings in the DAQ Assistant.  I do not have that and cannot see your settings.

Lynn