how to measure velocity with trigger

[madness]

Hi all.

I make an acquisition of sensors : pressure, velocity, temperature.

The datas are stored in binary files (because of data size).
The I post-process the data to convert voltage signal into value (for example : voltage into pressure...)
No problem to process the pressure and the temperature.
The problem is the velocity.
With the card I use, I cant make a numeric acquisition of the velocity. Thus, the datas are all take in analogic.
Then, the velocity is in analogic.

What I want to do :
I "just" want to convert velocity data into velocity.
1-
I know that I need a trigger to do it. But, how can I measure the velocity using a trigger with analogic datas?
2-
The datas have to had the same number of points for every sensors. Then, if I made a trigger conversion, I'll have the velocity every 10-20-...-n points. How can I do an average, to have the same value between 2 measurements of the trigger.

example :
The 20 first velocity points are : 0 5 5 0 0 5 5 0 0 5 0 5 0 5 0 5 5 0 0 5 5 0 0
Give the velocity result of : 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 1 1 1 1 1 1 1 1 or something like that.

The idea is to have as many points of velocity than the binary velocity data.

Thanks in advance for your help.
Please let me know if there is any point that is not very clear.

[SanaaT]

---

madness a écrit:
Hi all.

I make an acquisition of sensors : pressure, velocity, temperature.

The datas are stored in binary files (because of data size).
The I post-process the data to convert voltage signal into value (for example : voltage into pressure...)
No problem to process the pressure and the temperature.
The problem is the velocity.
With the card I use, I cant make a numeric acquisition of the velocity. Thus, the datas are all take in analogic.
Then, the velocity is in analogic.

What I want to do :
I "just" want to convert velocity data into velocity.
1-
I know that I need a trigger to do it. But, how can I measure the velocity using a trigger with analogic datas?
2-
The datas have to had the same number of points for every sensors. Then, if I made a trigger conversion, I'll have the velocity every 10-20-...-n points. How can I do an average, to have the same value between 2 measurements of the trigger.

example :
The 20 first velocity points are : 0 5 5 0 0 5 5 0 0 5 0 5 0 5 0 5 5 0 0 5 5 0 0
Give the velocity result of : 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 1 1 1 1 1 1 1 1 or something like that.

The idea is to have as many points of velocity than the binary velocity data.

Thanks in advance for your help.
Please let me know if there is any point that is not very clear.

---

Hello,

To respond to your question, I need more information :
1 - The device you use.
2 - Driver and version
3 - Version of LV

Have you any example that reproduce the problem?

Waiting for your response.

Sanaa T
National Instruments France

[madness]

dear sanaaT

I dont have a ni instrument, but a contec acquisition card, that work well.
The labview I use is 7.1 .

In fact, re-reading the explication of the problem, I think i can have a easyer wait to do it.

All I want is to "translate" voltage data (frequency is proportionnal to velocity) into velocity data.
I think I have to use a couple of points to have the velocity information.

I think it's easyer to understand with a picture ( excuse me for the style of the picture, I have made it with paint)

[SanaaT]

---

madness a écrit:
dear sanaaT

I dont have a ni instrument, but a contec acquisition card, that work well.
The labview I use is 7.1 .

In fact, re-reading the explication of the problem, I think i can have a easyer wait to do it.

All I want is to "translate" voltage data (frequency is proportionnal to velocity) into velocity data.
I think I have to use a couple of points to have the velocity information.

I think it's easyer to understand with a picture ( excuse me for the style of the picture, I have made it with paint)

---

Hello Madness,

Do you acquire TTL signal or analog signal?
Can you give me more information about your acquisition device?

You can also use the conversion VIs that you can found on the Functions Palette>>Numeric>>Conversion.

Sanaa T
National Instruments France

[madness]

sanaaT Thank you for your help :yes:

I use an analogic acquisition card.

The device is
CONTEC Analog I/O PC Card
ADA16-32/2(CB)F

32 analogic Inputs, high sample frequency.
But, I cant change the input way to acquire datas.
All I can have is an analogic array of datas, that I neeed to compute, to translate it into velocity.

...

[SanaaT]

Hello Madness,

It will be hard to tell you how to do the exact conversion. However, I send you some documents and example about corresponding signal processing in LV :
http://zone.ni.com/devzone/conceptd.nsf/webmain/9034002fc17fece586256cdb007457b6
http://zone.ni.com/devzone/conceptd.nsf/webmain/bfc420d779576b0a06256a03000b2c63
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3E96556A4E034080020E74861&p_node=DZ52014&p_source=external

Using NI device, the measurement of velocity is relatively simple using counters.
You can found, in the link below, the method that we use to do that :
http://zone.ni.com/devzone/conceptd.nsf/webmain/6f25cba2cd73417786256869005e5fc3

Then don't forget that there are some conversion functions in Functions Palette>>Numeric>>Conversion

Hope this help.

Sanaa T
National Instruments France

[madness]

I will test it this week, hoping this is helpfull.

Thanks a lot for you help 😉

I'll feedback the result of this.