by pizza » Sun May 30, 2010 12:01 pm
Hi Tom,
the taus that I use are
float taus[12]= {0.1, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024}; //note: unit = seconds
as these are equal intervals on the allanvariance log-log graph.
Tau is the averaging time used on the bias.
A 24 hr sample will have 86400*100 samples on a 100Hz sampling rate.
If tau = 1s, the samples are divided into 86400bins(i.e no. bins = total no. samples/samples in each tau). The samples in each bin are averaged. Then the allan variance is calculated. this is repeated for every tau. for tau=2s, there will be 43200bin etc. the less number of bins will cause higher error rate i.e ε(%)=100/√(2(bins-1)). A 2.4 hr sample will have less number of bins etc.