For something more sophisticated try the following example:-
Basic DC-RMS Measurement.vi
"Demonstrates how to compute the DC and RMS value of a signal. You can specify either linear or exponential averaging and choose the type of window for the measurement. You can create different types of signals using the Test Signal Generator Parameters."
With the example you can simulate noise on a signal, change the filtering type and the effect on the DC value.
Hope this is what your looking for.
