What is the difference between the express Integration (time domain math) and the numerical integration fuction from the Sound and Vibration Toolkit?

[Agile]

This might be a stupid question with a simple answer.  We're working on a project that requires acceleration, velocity, and distance data over time.  We're using the NI 9234 in a compactDAQ chassis connected to an accelerometer.  The accelerometer is attached to a cantilevered plastic subject (rectangular) that is "plucked" -- sort of like a ruler over the edge of a table sprung like a diving board.  We're acquiring at about 2k samples/sec and using the Sound and Vibration Toolkit's integration VI to derive velocity & distance.  Charting it, this is what we get:

We set up a task and used the defaults for the 9234 to convert voltage to g.  But "g" is both an SI and English unit (m/sec^2 or ft/sec^2). 

My question is, charting it, what would be the units and scale for both velocity & distance?

[Agile]

Oops. I see that the title of the post doesn't match the question in the post. It's because I started the process with one question and then posted another, not knowing it would use my original question as the title. Both questions are valid, but the units question is more critical to finishing our job.

[Henrik_Volkers]

---

We set up a task and used the defaults for the 9234 to convert voltage to g.  But "g" is both an SI and English unit (m/sec^2 or ft/sec^2). 

My question is, charting it, what would be the units and scale for both velocity & distance?

---

 First : g is not a SI !

The nice thing about the SI- units is that they even work together with math 😉 a  or have you seen a distance measured  0.10193679918451 gs² (= 1m)

So if you feed  m/s² into an (time) integrator you receive velocity in m/s , repeat it and you get distance in m .

[TheStudent]

Henrik,

Thanks for responding.  Here's my data below.  Would you be so kind to explain what you mean by this statement: 

""The nice thing about the SI- units is that they even work together with math a  or have you seen a distance measured  0.10193679918451 gs² (= 1m)

So if you feed  m/s² into an (time) integrator you receive velocity in m/s , repeat it and you get distance in m .""

the information is in English the displacement is "INCHES".  An additional question is "WHAT IS 5.11756?"   Is it "g's"?

5	Time (sec)	Acceleration (g)	Velocity	Displacement
3	Date	2010-06-29_11:04:42
1787	0.870117	5.117156	28.8235	0.173253
1788	0.870605	5.117156	39.43966	0.18988
1789	0.871094	5.117156	48.70714	0.211358
1790	0.871582	5.117156	56.70183	0.237046
1791	0.87207	5.117156	63.49703	0.266339
1792	0.872559	5.117156	69.16351	0.298668
1793	0.873047	5.117156	73.76955	0.333498

  Thanks

Rick "TheStudent" 

Greetings from Germany
Henrik

[Henrik_Volkers]

An additional question is "WHAT IS 5.11756?"   Is it "g's"?

Sorry Rick, my crystal ball is in recalibration 😉

As for now it's a meaningless number for me.

You are the only one who can answer that question 😮

But lets have a look into the measuring chain:.

What sensor are you using? 

Do you have any information about it's sensitvity  {mV, pC}/{g, m/s²} 

Offset?, DC included?

Do you use an additional amplifier/signal conditioner? If Yes what's the transferfactor S?

What are you reading with your DAQ? Voltages?

[Agile]

Henrik,

This is Rick under Darrell's signon.  We are all working on the same Project.

In response to your further questions to me:

An additional question is "WHAT IS 5.11756?"   Is it "g's"?

Sorry Rick, my crystal ball is in recalibration

As for now it's a meaningless number for me.

You are the only one who can answer that question

But lets have a look into the measuring chain:.

Q1 What sensor are you using?

A1  The sensor we're using is a Dytran Instruments model 3056B3.  It is an IEPE accelerometer and has a sensitivity of 492.9 mV/g.  There's no BW limit between 20 & 10kHz.  The frequency response is pretty solid between them.  You're right about the time scale and the 10Hz highpass.

Q2 Do you have any information about it's sensitvity  {mV, pC}/{g, m/s²}

A2 see above

Q3Offset?, NO   DC included?

A3 NO

Q4Do you use an additional amplifier/signal conditioner?  NO  If Yes what's the transferfac

tor S?

A4 NO

Q5What are you reading with your DAQ? Voltages?

A5 voltages

Thanks for your interest in our exercise.  Much appreciated.

Speak with you soon.

RicK - TheStudent