DASYLAB : start acquisition on rising edge during a certain period of time

[M.Charbonneau]

Hello,

I would like to know how to do on Dasylab to start acquire data on rising edge and during 0.6s exactly.

Secondly, I've a little problem with the module "Integer". I displayed an acceleration and I would like to have the speed and position with a double integer but I did'nt find how to do this on Dasylab...

Thanks,

Morgane Charbonneau.

[SAMUEL_NIF]

Hello,

do you know this link?

http://digital.ni.com/public.nsf/allkb/AE0A4D71F0CD603786256D9C0075B95B?OpenDocument

http://digital.ni.com/public.nsf/allkb/91D44FC21F0DF0CE86256BB1003F6CD9?OpenDocument

http://digital.ni.com/public.nsf/allkb/77F973851F041E0F86256BB1003EB94C?OpenDocument

Regards

[TomRizzo · Accepted solution]

For the triggering, you need to use a relays with control signal and block the output, the output will then go to the write data module.

This will store data only when the control signal of the relay is high (5).

If I remember correctly you will need to take the accel signal going through a high pass filter 0.5Hz and then going through two integrator modules.

Did you try this way?

[CJ_Butler__DASYLab_Pro]

Hi,

To integrate and double integrate in the TIME domain you need to use the integrate module twice.

To integrate and double integrate in the FREQUENCY domain, use the FFT module. At the bottom is a selection to differentiate, double-differentiate, integrate or double-integrate in the FREQUENCY domain. The output will be a frequency block with the amplitude integrated or differentiated for each frequency line. 

[M.Charbonneau]

Thanks for your answers & advices, I've added a combi trigger just before the relay, and it works! 🙂

But why do you need to take the accel signal going through the high pass filter? My sampling rate is 1000Hz, is it necessary for suppressing noise?

[JackSprat]

Blocking DC stops inevitable drift of output signal till limiting occurs - or numerically the value creeps towards infinity - pos or neg.

Dave the Rave

[TomRizzo]

Sorry fo the delay but Dave answered it perfectly.

Thank you

[M.Charbonneau]

I'm sorry but I don't understand what are you talking about...? The accel signal itself? The filter? The relay?

[JackSprat]

With a cup of coffee in hand - consider and understand what 'Integration' is and does as a mathematical process.

Consider then what happens if you have a small but non-zero and steady input signal, and you integrate this.

If you can see the result here then you will see the need to supress any residual or standing 'average value' in your otherwise dynamic source signal.

The Hi pass filter is removing any existing average offset from your electronics.

Dave the Rave.