The two modern standardized test methodologies in use are the Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives or C.I.P.
The piezo measuring device (transducer) is positioned at a distance of 25 millimetres (0.98 in) from the breech face when the length of the cartridge case permits that, including limits.
In a rifle cartridge case like the .308 Winchester, the TDCC M = 25.00 value denotes the transducer must be positioned at a distance of 25 millimetres (0.98 in) from the breech face.
nomenclature), the TDCC M = 12.50 value denotes the transducer must be positioned at a distance of 12.5 millimetres (0.49 in) from the breech face.
almost exclusively uses one type of piezoelectric sensor (named "channel sensor") made by the Swiss company Kistler that requires drilling of the cartridge case before firing the proofing cartridge in a specially made test barrel.
This measurement is referred to as the "offset" and makes allowance for the "loss" of that gas pressure prior to the cartridge case coming in contact with the transducer and generating the impulse.
Other benefits of the SAAMI conformal transducer are: very adaptive to the high volume quality control testing demands of commercial and law enforcement ammunition production; protection of the transducer from direct exposure to the high temperature combustion gases and hence a comparatively long service life; 80,000 psi (551.6 MPa) maximum working pressure.
[8] A low cost method of gathering pressure data uses a resistive stress gauge attached to the exterior of the chamber.
Because this system does not require a specialized test barrel, only a firearm that has an accessible external chamber wall, it is much lower cost.
This causes high frequency oscillations of the pressure sensor (approx 200 kHz for a Kistler 6215 transducer) and this requires electronic filtering with the drawback that filtering also affects the lower harmonics where a peak is found causing a slight error in the measurement.
This slight error is not always well mastered and this causes a lot of discussion about the filter order, cutoff frequency and its type (Bessel or Butterworth).