synchronous start of measurement

[Bernd Schoofs]

Hello!

I want to measure different channels with different scanrates. The Hardware
supports it. The measurement has to start simultanously. When I use the VI
"AL acquire waveform" the channels are acquired sequential and with other
VI's I can't set different scanrates for each channel. How can I solve this
problem?

Thanks in advance

Bernd Schoofs

[Oleg]

May be I'm not right but I think that your problems are because of only one ADC on your board. If your board has only one ADC it has to read channels sequential with switching from one channel to another. This is because you have actually only one device to read many channels.
If you want to read some channels more often than others you can set the sequence of channels for example as
1,2,2,1,2,2,1...
in this case the channel "2" will be read 2 times often than channel "1". But in any case they will not be read simultanously.

Oleg Chutko.

[Hugh]

Why not sample all of the channels at the sample rate required by your
highest bandwidth
signal and then undersample the data from those channels that don't
require such a high rate
afterwards? Sure, it's a waste of memory, but memory is cheap these days 😉

Hugh

Bernd Schoofs wrote:

>Hello!
>
>I want to measure different channels with different scanrates. The Hardware
>supports it. The measurement has to start simultanously. When I use the VI
>"AL acquire waveform" the channels are acquired sequential and with other
>VI's I can't set different scanrates for each channel. How can I solve this
>problem?
>
>Thanks in advance
>
>Bernd Schoofs
>
>

[Filipe A.]

Bernd;

The easiest and cleaner way to do that is by sampling all channels at the fastest Scan Rate required by the fastes channel, and then disregards some points of the other channels, so you can construct the array with the points acquired at different sampling rates.
Hope this helps.
Filipe