Anti-Alias Filter vs CPU load

[FrankL]

Hi,

I read the Anti-Alias help documentation of the dash manager and some stuff is still unclear to me.

1. Let say I logging a damper position sensor at 1kHz, should I use a Anti-Alias Filter?
Should I understand that the AI of the C185/187 is processing the signal at a high rate that 1kHz?

2. Does removing the Anti-Alias Filter reduce the CPU load? If yes, how much, any estimation in % of the logging rate?
What would be the best practice, logging at double the sampling rate needed for a channel or using the Anti-Alias Filter?

3. If some information are being broadcast on a CAN BUS at 1kHz and I am logging this channel at 1kHz, is there any use for the Anti-Alias Filter?

Thanks, François

[NathanB]

1. If you are logging a channel at that speed, the anti aliasing filter should be removed. Wired inputs such as AV's are sampled at 4khz, however the anti alias filter is intended when you are logging at a rate far lower that the update of the channel, and WANT each logged sample to be an average of the received values in the time between each sample, as opposed to the sample being the value at that moment in time.

2. Yes, but it is tricky to quantify, as it varies based on a number of factors. As an example, I have a log set with 960 channels at varying rates. 35 channels had AA filtering turned on. I saved 0.2% CPU turning the AA filter off on the 35 channels.

3. No