Position from acceleration data in DIAdem

[dzehner2]

I'm working on a project where I'm measuring the acceleration of a piece of equipment in our plant using 3 single axis accelerometers. I have 2 of them measuring the X axis (to detect when it is swaying from side to side) and one measuring the Z axis (to show when the equipment is moving up and down). I'm trying to use DIAdem to analyze the data, and I've run into a problem when I integrate the raw data to get posisition. Here's a screenshot of what I'm experiencing:

The top channel is the acceleration from one of the X axis sensors, the middle is the 1st integration, and the bottom is the 2nd. I would expect the veloctiy curve to look similar to the acceleration curve, but out of phase by 90 degrees. The position curve should also have a similar shape. What am I missing here? I'm new to using DIAdem to analyze data, so any help is appreciated. Thanks!

[HeroOfHyrule]

How are you running the calculations to determine your second and third graphs? Could you post the equations you are using to produce these?

[dzehner2]

I'm actually just using the Integrate function from the Basic Mathematics menu in the Analysis tab. Then I do a second integration on the results channel of the first. I think I may be missing an offset correction or something...

[Brad_Turpin]

Hi dzehner2,

What are you using as the X channel in the integration dialog?

Brad Turpin

DIAdem Product Support Engineer

National Instruments

[dzehner2]

That could be the issue... I'm just using the blank time channel from the accelerometers. Should I generate a time channel in DIAdem?

[hnesmith]

Hey dzehner2, 

You could generate a time channel in DIAdem or log the time alongside your acquisition. How are you logging the data? 

[dzehner2]

I'm using a NI 9184 compact DAQ chassis with a NI 9234 signal conditioner with analog accelerometers for sensors. I'm using Signal Express to generate a .tdms log file. I've just been using the internal clock for my X-axis when graphing the data. Do I need to create a time channel or use an external clock?