I have been conducting some bench experiments with my Bohli taut-band
bellows with capillary leak vario to determine the system time constant.
The set-up is a 0.45 liter glass vacuum flask attached to the vario with .5
meter of 3mm Tygon tubing with a 1cc syringe teed into the tubing at the
flask. The static/TE port on the vario is left open to the atmosphere.

By injecting 1cc of air into the flask, I simulate a sharp edged thermal
encounter. This causes the vario reading to instantly jump to about 5
meters per second up and then decay to zero. I am starting a timer at
various points on the scale as the needle falls and timing the decay to half
that value. (For example, start timer at 4 MPS and stop at 2 MPS) I am
consistently getting 7 seconds for this decay interval.

The Sage web site suggest the test should be for the decay to 37% of the
initial value. Using 37%, the decay interval is 11 seconds. Sage claims 1
second decay.

Repeating the 50% test on a 5MPS vane-in-torus type vario resulted in values
of only 2.5 seconds.

The decay values for the Bohli vario seem large to me. I am starting to
suspect that the 0.45 capacity is far too large for the size of the
capillary in the Bohli.

Is this type of experiment of any real value? Any comments?

Bill Daniels