SP G2 uses Buhlmann algorithm, it has a combination of MB and PDIS in this case you can choose to activate it or not.
From Wikipidia:
PDISs are intermediate stops at a depth above the depth at which the leading compartment for the decompression calculation switches from ongassing to offgassing and below the depth of the first obligatory decompression stop, (or the surface, on a no-decompression dive). The ambient pressure at that depth is low enough to ensure that the tissues are mostly offgassing inert gas, although under a very small pressure gradient. This combination is expected to inhibit bubble growth. The leading compartment is generally not the fastest compartment except in very short dives, for which this model does not require an intermediate stop.[22] The 8 compartment Bühlmann - based UWATEC ZH-L8 ADT MB PMG decompression model in the Scubapro Galileo dive computer processes the dive profile and suggests an intermediate 2-minute stop that is a function of the tissue nitrogen loading at that time, taking into account the accumulated nitrogen from previous dives.[22] Within the Haldanian logic of the model, at least three compartments are offgassing at the prescribed depth - the 5 and 10 minute half time compartments under a relatively high pressure gradient. Therefore, for decompression dives, the existing obligation is not increased during the stop.[29]
A PDIS is not a mandatory stop, nor is it considered a substitute for the more important shallow safety stop on a no-stop dive. Switching breathing gas mix during the ascent will influence the depth of the stop.[22]
The PDIS concept was introduced by Sergio Angelini
From the SP G2 manual :
Profile Dependent Intermediate Stop (PDIS), as described in the chapter: PDIS (Profile Dependent Intermediate Stop), has been extended to both nitrogen and helium gases. The optimal off-gassing depth will be indicated when PDIS is enabled. PDI stops are not obligatory, but will potentially assist in reducing possible bubble formation.
3.10 PDIS (Profile Dependent Intermediate Stop)
3.10.1 Introduction to PDIS The main purpose of a dive computer is to track your nitrogen uptake and recommend a safe ascent procedure. Diving within the so called no-stop limits means that at the end of the dive you can ascend directly to the surface, albeit at a safe ascent rate, while for dives outside of the no-stop limit (so-called decompression dives), you must perform stops at certain depths below the surface and allow time for excess nitrogen to be expelled from your body before finishing the dive. In both cases, it can be beneficial to stop for a few minutes at an intermediate depth between the maximum attained depth during the dive and the surface or, in case of a decompression dive, the first (deepest) decompression stop. An intermediate stop of this kind is beneficial as soon as the ambient pressure at that depth is low enough to ensure that your body is predominantly off-gassing nitrogen, even if under a very small pressure gradient. In such a situation, you can still cruise along the reef and enjoy the dive while your body gets a chance to slowly release nitrogen.
In recent times, so called “deep” stops have been introduced in some dive computers and tables, defined as half the distance from the dive’s maximum depth and the surface (or the lowest decompression stop). Spending 2 or 15 minutes at 30m/100ft would result in the same deep stop at 15m/50ft. With PDIS, as the name suggests, the G2 interprets your dive profile and suggests an intermediate stop that is a function of your nitrogen uptake so far. The PDI stop will therefore change through the course of the dive to reflect the continuously changing situation in your body. Along the same lines, PDIS will account for the accumulated nitrogen from previous dives; hence, PDIS is also repetitive-dive dependent. Conventional deep stops completely ignore these facts.
3.10.2 How does PDIS work?
The mathematical decompression model in the G2, called ZH-L16 ADT MB PMG, tracks your decompression status by dividing your body into 16 so-called compartments and mathematically following the uptake and release of nitrogen in each with the appropriate laws of physics. The various compartments simulate parts of your body such as central nervous system, muscles, bones, skin and so on. The depth of the PDI stop is calculated as that at which the leading compartment for the decompression calculation switches from on-gassing to off-gassing, and the diver is advised to perform a 2-minute stop above the displayed depth (this is the opposite of a decompression stop, where you are asked to remain just beneath the displayed depth). During this intermediate stop, the body is not taking up any more nitrogen in the leading compartment, but rather releasing nitrogen (though under a very small pressure gradient). This, combined with the relatively high ambient pressure, inhibits bubble growth. It should be noted that the 4 fastest compartments, up to 10-minute half-times, respectively, are not considered for the determination of the PDI stop depth. This is due to the fact that these compartments are only “leading” for very short dives, for which an intermediate stop is not required at all.
This DC don't have GF but have L0 to L9 being L0 no conservationism and L9 the most conservationist.
This computer have multiple mix gases options and PMG that dictates gas switches depending on you O2 concentration up to 8 gases, and trimix
How far off is this DC without GF to be a good technical DC ?
Have any of you done Serious Tec Diving with the UWATEC ?
Some time ago many used certain UWATEC DC models for tec diving and now opted for the same Algorithm but with GF.
*-* what have you notice a big difference in how you feel between this two.
*-* will you dive a UWATEC DC again for tec diving if you don't have one with GF in that moment
*-* It seems logical to extend you last stop at 6m, will you use the UWATEC DC, but padd the last stop knowing what your prefered GF dictates for that particular dive.
This thread is not about a selection of DC, is about the differences.
From Wikipidia:
PDISs are intermediate stops at a depth above the depth at which the leading compartment for the decompression calculation switches from ongassing to offgassing and below the depth of the first obligatory decompression stop, (or the surface, on a no-decompression dive). The ambient pressure at that depth is low enough to ensure that the tissues are mostly offgassing inert gas, although under a very small pressure gradient. This combination is expected to inhibit bubble growth. The leading compartment is generally not the fastest compartment except in very short dives, for which this model does not require an intermediate stop.[22] The 8 compartment Bühlmann - based UWATEC ZH-L8 ADT MB PMG decompression model in the Scubapro Galileo dive computer processes the dive profile and suggests an intermediate 2-minute stop that is a function of the tissue nitrogen loading at that time, taking into account the accumulated nitrogen from previous dives.[22] Within the Haldanian logic of the model, at least three compartments are offgassing at the prescribed depth - the 5 and 10 minute half time compartments under a relatively high pressure gradient. Therefore, for decompression dives, the existing obligation is not increased during the stop.[29]
A PDIS is not a mandatory stop, nor is it considered a substitute for the more important shallow safety stop on a no-stop dive. Switching breathing gas mix during the ascent will influence the depth of the stop.[22]
The PDIS concept was introduced by Sergio Angelini
From the SP G2 manual :
Profile Dependent Intermediate Stop (PDIS), as described in the chapter: PDIS (Profile Dependent Intermediate Stop), has been extended to both nitrogen and helium gases. The optimal off-gassing depth will be indicated when PDIS is enabled. PDI stops are not obligatory, but will potentially assist in reducing possible bubble formation.
3.10 PDIS (Profile Dependent Intermediate Stop)
3.10.1 Introduction to PDIS The main purpose of a dive computer is to track your nitrogen uptake and recommend a safe ascent procedure. Diving within the so called no-stop limits means that at the end of the dive you can ascend directly to the surface, albeit at a safe ascent rate, while for dives outside of the no-stop limit (so-called decompression dives), you must perform stops at certain depths below the surface and allow time for excess nitrogen to be expelled from your body before finishing the dive. In both cases, it can be beneficial to stop for a few minutes at an intermediate depth between the maximum attained depth during the dive and the surface or, in case of a decompression dive, the first (deepest) decompression stop. An intermediate stop of this kind is beneficial as soon as the ambient pressure at that depth is low enough to ensure that your body is predominantly off-gassing nitrogen, even if under a very small pressure gradient. In such a situation, you can still cruise along the reef and enjoy the dive while your body gets a chance to slowly release nitrogen.
In recent times, so called “deep” stops have been introduced in some dive computers and tables, defined as half the distance from the dive’s maximum depth and the surface (or the lowest decompression stop). Spending 2 or 15 minutes at 30m/100ft would result in the same deep stop at 15m/50ft. With PDIS, as the name suggests, the G2 interprets your dive profile and suggests an intermediate stop that is a function of your nitrogen uptake so far. The PDI stop will therefore change through the course of the dive to reflect the continuously changing situation in your body. Along the same lines, PDIS will account for the accumulated nitrogen from previous dives; hence, PDIS is also repetitive-dive dependent. Conventional deep stops completely ignore these facts.
3.10.2 How does PDIS work?
The mathematical decompression model in the G2, called ZH-L16 ADT MB PMG, tracks your decompression status by dividing your body into 16 so-called compartments and mathematically following the uptake and release of nitrogen in each with the appropriate laws of physics. The various compartments simulate parts of your body such as central nervous system, muscles, bones, skin and so on. The depth of the PDI stop is calculated as that at which the leading compartment for the decompression calculation switches from on-gassing to off-gassing, and the diver is advised to perform a 2-minute stop above the displayed depth (this is the opposite of a decompression stop, where you are asked to remain just beneath the displayed depth). During this intermediate stop, the body is not taking up any more nitrogen in the leading compartment, but rather releasing nitrogen (though under a very small pressure gradient). This, combined with the relatively high ambient pressure, inhibits bubble growth. It should be noted that the 4 fastest compartments, up to 10-minute half-times, respectively, are not considered for the determination of the PDI stop depth. This is due to the fact that these compartments are only “leading” for very short dives, for which an intermediate stop is not required at all.
This DC don't have GF but have L0 to L9 being L0 no conservationism and L9 the most conservationist.
This computer have multiple mix gases options and PMG that dictates gas switches depending on you O2 concentration up to 8 gases, and trimix
How far off is this DC without GF to be a good technical DC ?
Have any of you done Serious Tec Diving with the UWATEC ?
Some time ago many used certain UWATEC DC models for tec diving and now opted for the same Algorithm but with GF.
*-* what have you notice a big difference in how you feel between this two.
*-* will you dive a UWATEC DC again for tec diving if you don't have one with GF in that moment
*-* It seems logical to extend you last stop at 6m, will you use the UWATEC DC, but padd the last stop knowing what your prefered GF dictates for that particular dive.
This thread is not about a selection of DC, is about the differences.
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