Witschi ProofMaster - Reference to Standard ISO 22810

Description
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A negative leak rate can be caused by a number of factors, e.g.:
• Elastic deformation of the test specimen;
• Thermal influences.
Over a longer measurement duration, the ProofMaster measurement
algorithm compensates for these influences and displays a more
accurate result. This makes it more reliable and faster than an algorithm
used for conventional deformation measurement.
However, the end result may also display a negative leak rate. This
usually occurs with leak-tight test specimens, in which case
compensation cannot be fully performed. However, the reliability of the
measurement is still guaranteed.
Significant negative leak rates indicate that the automatic
compensation was insufficient for the test specimen. Manually setting a
longer measurement time may remedy this.
If unclear, please contact customer service, see Technical support
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4.7 Reference to standard ISO22810
Leak-tight watch in
accordance with
standardISO 22810
Standard ISO 22810 defines that a watch shall be classified as leak-
tight if less than 50 µg of air penetrates the watch per minute at a test
pressure of 2 bar.
Relationship between
volume and deformation
The ISO 22810 standard does not take into account the volume of the
watch. This means that the leak rate of 50 µg per minute applies to all
watches, regardless of their size.
When testing according to the principle of deformation, the reversion
depends on the free volume in the watch. In a watch with a small
volume, the reduction in deformation is more pronounced with the same
amount of penetrating air. The free volume must be programmed in the
watch for a standard-compliant test.
Interpretation of ISO 22810
The standard is based on a pressure of 2bar or 0.5bar. No limit value is
specified for other pressures. It is therefore assumed that the limit of
50 µg per minute applies for all test pressures.