processing of aquired signal during aquisition (arrays?)

[Kostya 74]

Hello,
I'm aquiring a voltage signal from a thermistor using DAQ and Labview. I'm using "for-loop" in Labview for that. Is it possible to take my previous readings of the voltage signal (through A/D channel), say, V(i-1), compare it to its current value V(i) and if a comparison condition holds - "freeze" V(i-1) and feed it continuously to a D/A channel,etc.
I'm basically trying to work with "arrays" in Labview, but can't get the voltage array previous values during the aquisition and manipulate with it during the aquisition.
Thanks.

[IanW]

Kostya

To get at the V(i-1) value just use a shift register, then make your comparison and use a select. I'm not sure whether your array is for the history of one thermistor or several different thermistors. Take a look at the picture it shows both a single channel and 3 channels. To initialise the shift register you can do a single measurement before you go into the loop.

[Kostya 74]

Thanks, lanW. In fact, I tried to use the shift register, but results are same as if no shift register used. I checked it by wiring two "index array" icons with different indexes to the output of my "build array" - they give zero values - I monitor it by attaching "indicators" to the "index array" icons.
What do you think about it?
Also, where do I need to wire the right-hand shift register - to the output of the "build array" or to one of its inputs (one is the left-hand shift register, another one is my signal).
Thanks.

[IanW]

It's hard to see where you are going wrong, maybe you could attach your program or an example which demonstrates your problem.