An ANSTI machine replicates the action of breathing from a regulator at depth. It provides its results in a scientific and quantitive way, without the emotional or mental responses of a human diver.
The computer linked to the machine displays a pressure/volume diagram that evolves from each breath cycle. Parameters for the performances achieved are set and these performances vary according to ambient depth, supply pressure and the air demanded.
For our regulator test we demanded air in the amounts required by a very large, hard working diver - around 63 litres per minute. Many training agencies suggest
25 lpm for air requirement calculations.
The regulator is subjected to increasing depth, the machine continues to breathe, and the computer takes continuous readings of inhalation and exhalation pressures, and the work of breathing. This is plotted in the familiar pressure/volume diagram.
In the past we have taken each regulator down to the point where the inhalation pressure exceeds 25 millibars. This has given us a "depth rating" at the point at which the regulator "failed".
However, some would say that this is misleading, because the regulator does not "fail" to give air as such - it is just that the inhalation effort exceeds the limit previously adopted for test standards.
This time we took each regulator down to a target depth of 50m and compared the work of breathing and the shape of the pressure/volume diagram achieved at that moment. Surprisingly, some regulators went off the scale and we had to reduce the test depth to get a satisfactory result.
The machine makes a new graph for each breathing cycle and the operator selects the specimen breath cycle to print out.
A typical ANSTI read-out. Our example shows the Apeks TX40.
