Delays between analog inputs 
Author Message
 Delays between analog inputs

Hello Vince,

I am not very clear about your questions but I'll to try to answer
from what I best understand.

1) You cannot synchronise your channels. By that I mean that the
acquisition cannot be 'simultaneous'. There will be a small time lag
between data collected from any two channels and this is usually in
the order of a few microseconds to milliseconds (depending on how fast
your vi and daqboard are). You could consider using a simultaneous
sampling card but they are expensive. Or you may use a sample and hold
circuit between your sensors and daqboard.

2) What do you mean by delay one or more channels? The acquisition
speed and interchannel delay will be the same for all channels. You
may use software averaging or selection or delays to make data from
some channels processed more frequently than other channels.

Let me know if I am on the right track and we could discuss this

Success to you!

- Gurdas

Wed, 21 Dec 2005 15:44:23 GMT  
 Delays between analog inputs
It seems that my question was not very clear. I just want to delay
some channels to synchronize the acquisition of my system. I want that
the acquition of all signals coming from different sensors or
instruments start physically simultaneously.
For example : at t=0 channels 1 to 5 start, and 5s later channels 6 to
10 start, because the elements connected to the channels 6 to 10 have
a faster time response and I know it is 5s faster than elements
connected to channels 1 to 5.
Doing so I will get synchronize data. At the present I have to switch
manually my data after the acquisition. but there are so many data
that it is not only long and boring but source of mistakes.

Fri, 23 Dec 2005 16:22:34 GMT  
 Delays between analog inputs
The term 'simultaneous' and 'synchronous' can have wide ranging
meanings. Like, you might desire the interchannel skew to be either
just 1 second or 10 nanoseconds!!
If the first is close to what you want, it can be accomplished with
the hardware you have. But if you are looking for simulatneous in the
real sense (say with 10 ns of delay) then the hardware you have will
not suffice. Usually such a demanding acquisition is for dynamic
signals like noise and vibration.

To implement your scheme use AI read twice in your program with a
delay loop of 5 secs inbetween. Use the index array function to derive
the channels you want from the AI Read array data.

- Gurdas

Fri, 23 Dec 2005 21:26:53 GMT  
 [ 3 post ] 

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