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albert kok

Using a mini-altimeter as a leak detector

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Commercial leak-detectors are based on the principle that a barometric underpressure (or: partial vacuüm) that is sucked in your housing with a hand pump, rises above a critical level. In that case a red LED on the detector starts blinking: probably a leak! If you already have a vacuüm pump, but no detector, a mini altimeter (basically a small barometer translating mbars in feets of altitude) can be very helpful. At least if you a have a transparent Ikelite housing. I use this little and cheap device ALTIMER ONE that I stick to the inside of the Ikelite housing. After the vacuüm is established (around 20 strokes) you read out the pressure in feets altitude (say 4000 fts). Giving you an objective indication of the pressure inside your housing. So you want to be sure that this reading doesnt change, say in the next couple of hours.

 

I haven't yet checked the altimeter reading during a dive. Its possible that the air pressure inside the housing may drop a bit, because of the decrease of water temperature (and cooler air inside the housing) with increasing depth. This will give you a higher reading on the altimeter. No reason to panic. Only a sudden lower reading on the altimeter means trouble. Apparently water is entering the housing, which causes a rise of the inside pressure Have fun!.

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Edited by albert kok
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Hello Albert,

 

I think people who are into rocketry use that device to record maximum altitude. Does it have a mode that allows you to continuously observe pressure changes within the housing. How long does it remain on? Something like that would certainly be an improvement over the usual red/green light indicators.

 

I see that there is also an "altimetertwo" and an "altimeter3." Do you know how they differ from yours. I think the altimeter3 can de controlled by an iPhone.

 

Right now, I'm using a rather large aneroid barometer the same way. However, once installed, it shifted some housing controls out of alignment - to fix that problem, I had to I shave quite a bite of material off the bezel and off the back of the thing.

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This gadget is made by a firm called 'jolly logic'..indeed for rocketry. The mode one altimeter costs round 45 US dollars. It also has a real time option; an online reading of the altitude in fts or meters. Another option is maximum altitude. The more expensive model altitude 3 indeed can be controlled with your Iphone.You can charge the battery via the USB port of your computer. 17 strokes of your vacuum pump corresponds with around 1800 meters altitude; which I think is around 180 mbar underpressure, There is some variation in the altitude reading dependent on the ambient temperature. A 10 degrees Celsius drop or rise in temperature will probably give you an altitude reading of 50 meter higher or lower than the preset 1800 meters, respectively. Thats is around 10 mbar variation.

Edited by albert kok

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