The Design
The Apeks TEK Gauge has a black face to help reduce glare and to preserve night vision in low-light environments. The numerals, intermediate markers and the single hand have a luminescent coating and glow when charged from a light source (usually a dive-torch).
The unit has a chrome-plated marine brass body with a tempered glass face. Its 52mm-diameter scale reads from 0-360 bar with a maximum working pressure of 300 bar, and weighed in at 200grm (without a hose) on my digital scale.
The instrument’s sealed and waterproof body houses a common Bourdon tube mechanism. This works on the principle that a curled-up metal tube tends to straighten when internal pressure is applied, causing the tip to move; the movement of the tip drives the hand via a geared mechanical linkage to indicate a reading against a fixed scale.
For safety reasons the back of the body has a blow-out disc that’s designed to fail and release internal pressure should the Bourdon tube rupture, thus preventing the glass face fragmenting outwards.
The gauge was supplied with an 80cm-long high-pressure rubber hose carrying a burst pressure rating of 1500 bar.

The Tests
The first thing I did was test the TEK Gauge for accuracy. This was something I couldn’t do without enlisting the help of a former colleague from the Fire & Rescue Service Breathing Apparatus Section.
The Fire Service’s technicians use precise measuring instruments to ensure the accuracy of their own contents gauges. When the TEK Gauge was tested it delivered a result of +/–2 bar, which the technician eloquently described as “a pretty accurate gauge” as he scoffed my blackmail lunch at the local boozer.
I like to mount my SPG using a simple but effective piston-clip that’s cable-tied to the end of the hose. Tec-diving purists will be wincing and firing off emails of condemnation to the Editor, followed by a detailed description of the proper way to do it using doubled-over O-rings or loops of nylon line, but the simple, cheap and nasty cable-tie method has never let me down – well, not as yet.
Under water, the weight of this instrument makes it negatively buoyant, and for that read “stable”. Once it’s clipped off on a well-placed BC D-ring, it’s always where you expect it to be throughout the dive.
This might not sound like a big deal, but when you’re constantly checking the reading (as you should be during a dive) it makes the operation as simple as possible.
The black face enabled the contrasting dial markings and, more importantly, the hand to stand out, so a quick glance is all that’s required to assimilate the information.
A red band between the 50 and zero bar markings enhances awareness, highlighting the fact that the dive should be over at that point, while maintaining a safety margin.

Conclusion
The humble SPG is a crucial instrument, and one that should receive more than a cursory glance (pun intended).
The Apeks TEK Gauge proved to be accurate, and it’s robust construction and well-considered layout keeps it simple and easy to read. It should last a lifetime.
I can’t think of a single negative comment to make, so I’ll finish with the same advice I used to give my trainee firefighters: “Gauge check, gauge check, gauge check, then check again.” One day that procedure might just save your life.

SPECS
PRICES: Gauge only, £61. With 80cm hose £90
MAX WORKING PRESSURE: 300 bar
SCALE: 0-360 bar
SIZE: 52mm diameter
DIAL: Black, luminescent numerals and hand
BODY: Chrome-plated marine-grade brass
WEIGHT: 200g (without hose)
CONTACT: www.apeksdiving.com/uk
DIVER GUIDE 10/10