SCXI incorrect measurement

[baycan]

Hi Maggie,

I am a little confused about the scanning techniques. From the link you gave:

Scan	Channel	Time (usec)
0	0	0
0	1	1
0	2	2
0	3	3
1	0	4000
1	1	4001
1	2	4002
1	3	4003
2	0	8000
2	1	8001
2	2	8002
2	3	8003

Table 1: Interval Scanning 

Scan	Channel	Time (usec)
0	0	0
0	1	1000
0	2	2000
0	3	3000
1	0	4000
1	1	5000
1	2	6000
1	3	7000
2	0	8000
2	1	9000
2	2	10000
2	3	11000

Table 2: Round Robin Scanning

I am confused because the number of channel switches is the same in both techniques. Just the timing is different. Isn't the good technique supposed to reduce the number of channel switches, possibly by buffering?

[MaggieAggie]

Hello Baycan, 

I apologize for my last link. I misunderstood what you were trying to do as Round Robin Scanning. Round Robin Scanning changes the spacing between sampling the channels. 

For your application, it would be best to use Software-driven scanning that Izzy had mentioned earlier. You were having trouble implementing it. Am I correct that you are using SignalExpress? Would you be able to program it in LabVIEW? 

[MaggieAggie]

Hello Baycan, 

I've been thinking about how to implement software driven scanning in SignalExpress. Make your DAQmx task for your first channel and choose N samples. Then, add a sequence step by going to Add Step >> Execution Control >> Sequence. In the configuration window, check "allow hardware reuse." Then, add another task for your other channel. This method will allow you to sample from one channel for N samples, then the next channel. 

This should minimize the clicking that you hear.