What is the average time to do a pass when data is read after a period of time?

[cpscdave]

Hi there,
I'm trying to model how much faster we will be able to pull data from a set of controllers.
I know how long it takes to read a single data point from each controller.
Right now we are reading each and every data point.

The change I would like to model is some of the data isn't read each pass. But instead read after a period of time during that next pass.

So if we have 2 sets of data A and B
Right now each pass reads A and B and takes x seconds

The change will result in
Pass 1: A & B
Pass 2: A
Pass 3: A
... so many seconds elapse:
Pass N: A& B

How do I figure out the average time it takes to do a pass in the second case??

Thanks :)

 

[mfb]

How does that look in time?

"We read A for two seconds, then B for two seconds, then A for two seconds, then A for two seconds,. ..."?
Then all you need is the average fraction B that gets read, multiply by the time it takes, add the time for A and you have your average time per pass.

 

[cpscdave]

Thats what I originally did.
The problem I ran into is when I follow that through:
A: Time to read the data each loop
B: Time to read the data on
C: the fraction of scans where B is read
Time = A + C*B

So now I need to figure out what C is which I figure is Time/M (M is how often to scan the data)
So solving that out I end up with Time = A*M/(M-B)
Which doesn't seem right.

 

[mfb]

Looks right to me.