Delays between analog inputs

[vince1970]

I work with a PCI-6033E board with 32 analog differential inputs. I use about 10 channels for analog signals acquisition from many sensors and instruments. My question is how to synchronize the whole system acquisition ? Is it possible to delay one or many channels ?
This because the time responses of each element of the system is not the same !
Thanks.

[Gurdas]

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 so
me channels processed more frequently than other channels.

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

Success to you!

- Gurdas

[vince1970]

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.
Thanks.

[Gurdas]

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