In engineering terms, this would be called a third-order low-pass filter consisting of three first-order low-pass filters placed in series. The third-order filter is characterized by the transfer function:

G(s) = (1/(tau*s + 1))^3.

Each first-order filter has a time constants of:

tau = averaging_time/3.

The initial values of the outputs of each of the three first-order filters can be set. However, they can only be set together, i.e., only one parameter is provided for all three of them. By default, they assume values of zero.