Apeks HP Wireless Transmitter (MH-8A)
- Compatible with Apeks DSX air integrated computer
- Wireless transmission of tank pressure to your computer
- Rated for depth up to {500 ft | 150 m}
- Includes user replaceable CR2 photo battery
- Also compatible with Aqualung, Aeris, Hollis, Oceanic, Shearwater, Sherwood, and Tusa air integrated computers
Apeks HP Wireless Transmitter (MH-8A)
Related Products
This tank pressure wireless transmitter is compatible the Apeks DSX dive computer. Also compatible with Aqualung, Aeris, Hollis, Oceanic, Shearwater, Sherwood, and Tusa dive computers that support hoseless air integration.
The transmitter is Nitrox Ready, rated for depth up to { 500 ft | 150 m }, and has a user replaceable, non-rechargeable and widely available CR2 photo battery. Although the official specifications reference the usual EN250 requirements for accuracy of mechanical pressure gauges, you can expect the ±5% full scale accuracy typical of digital gauges. The high pressure o-ring located at the base of the transmitter is a standard size AS568-012, oxygen compatible material while the battery cap o-ring used is size AS568-016, Nitrile (Buna-N) A70. Both o-rings are widely available and under normal circumstances neither o-ring requires routine replacement. The dive computer will display a low battery warning that indicates the transmitter number when the transmitter battery needs to be replaced.
The transmitter screws in to a high-pressure (HP) port of the first stage regulator mounted on the tank to be monitored. An antenna inside the dive computer receives the signals when it is positioned within { 72 in (6 ft) |1.8 m } of the transmitter and within a zone parallel or at a 45 degree angle to the transmitter. Best reception is achieved when the dive computer and transmitter are within { 3 ft | 0.9 m } of each other. During a dive you may at times move the dive computer so that is out of the signal pattern of the transmitter, resulting in a temporary interruption of the link. The link may also be interrupted if the dive computer is within { 3 ft | 0.9 m } of a running DPV or after a strobe light flashes. The link will be restored within 4 seconds after the dive computer is reoriented, moved back into range, or the interference clears. For technical diving, Dive Gear Express recommends following the best practice of also including a standard analog SPG on the regulator as a backup.
In rare cases, the body of some first stage regulator designs will have hose ports oriented such there is not room to accept a wireless tank pressure transmitter without interfering with hose routing. The solution is to use a standoff adapter, or some divers prefer to use a short 6-inch HP hose pigtail (do not forget the required Air Spool) in place of the standoff.
Officially, the Apeks branded transmitter is supported and warranted by Apeks for use with their DSX computer, not with other brands. However, this tank pressure wireless transmitter (OEM by Pelagic Pressure Systems = FCC ID MH-8A), is also compatible with those specific models of Aqualung, Aeris, Hollis, Oceanic, Shearwater, Sherwood, and Tusa brand dive computers that also support hoseless air integration with transmitters having that same MH-8A number. It is NOT compatible with Garmin brand dive computers.
| Brand | Apeks |
|---|---|
| SKU | APX-NS119115 |
| Weight | 0.450000 |
Customer Reviews
About Gas Time Remaining (GTR) Calculations
Some dive computers have the ability to monitor a sensor that allows them to provide a digital display of the gas pressure in the dive cylinder. This feature is often referred to as 'air integration' (AI) but since nearly all modern dive computers are capable of handing a variety of breathing gases the term air is a misnomer. A few of the AI computers go a step further and use the tank pressure to calculate an estimate of the breathing gas time remaining (GTR). There are a variety of different methods and formulas for GTR calculations but they all share limitations such that, for specific divers and specific dives, the GTR displayed by your computer can be wildly inaccurate.
Just to be clear, the accuracy of the GTR is not a limitation of the computer or the transmitter but because there are simply too many unknowns to make the GTR anything other than a gross approximation. Beyond the obvious factors such as environment, depth variations in a multi-level dive profile, ascent rates, and stop times; the divers gas consumption rate will vary greatly depending on changes in equipment configuration and exertion. For this reason, GTR estimates are meaningless on most technical dives and even some deeper sport dives, particularly if hunting.
Another factor that can affect the GTR depends on the algorithm used for making the estimate. Some methods require the diver to know and enter an RMV consumption rate along with the volume of gas available (i.e. 'tank size'). Other methods use an observed SAC rate to develop a prediction based on consumption history and may optionally require the cylinder rated service pressure be entered. Computers that calculate GTR based on observed SAC rate history are particularly problematic when the diver uses different capacity cylinders on different dives.
While the GTR can be useful in warning inexperienced sport divers when gas consumption is abnormally high, Dive Gear Express does not recommend relying upon dive computer GTR estimates to control or extend the dive time. Never allow the computer GTR estimate to become part of your dive plan, always closely monitor your actual tank pressure.
