Jump to content
pointy

Cheap vacuum indicator for "Housing Sentry"

Recommended Posts

I would like to fit my Ikelite housing with the "housing sentry", but the complete kit, which includes flashing red and green lights to indicate whether the vacuum is being maintained, costs $699. Alternatively, I could just buy the vacuum fitting and cap for about $200, and use a syringe and stopcock to withdraw air from the housing.

 

http://uwcamerastuff.com/housing_sentry_price.htm

 

To give me visual verification that the vacuum is being maintained I could place a small capped syringe inside the housing. As air is withdrawn, the plunger should rise and remain elevated as long as the vacuum is maintained. That wouldn't be quite as good as the complete kit, but it would save me $500.

 

Does anybody have a better idea for a low budget vacuum indicator? Do you think going the cheap route would leave me open to a disaster that could cost way more than $500?

 

John McCracken

 

 

 

 

 

 

 

 

 

Share this post


Link to post
Share on other sites

I dont think that it would work. I wouldnt think that the plunger would move if you lost pressure.

Share this post


Link to post
Share on other sites

I dont think that it would work. I wouldnt think that the plunger would move if you lost pressure.

Just now, I put a capped syringe inside a growler jug with a one hole stopper on top. Then I used a bicycle pump to pressurize the jug, which caused the plunger to move from the 12ml mark to the 6 ml mark. When I released the pressure, the plunger rose back to 12 ml. Prior to putting the syringe into the jug, I compressed the plunger to give a little extra pressure to help the plunger overcome friction against the barrel that would otherwise have kept it from returning to 12 ml.

 

That's the opposite of what you want to do with the housing sentry, but I did it this way because I didn't have the means to pull air out of the jug - In any case, the syringe did respond to pressure. If the syringe doesn't leak much over a period of several hours, this could work.

 

I'll try to do this right when I have the means to create a partial vacuum.

 

John McCracken

Share this post


Link to post
Share on other sites

John,

 

There is a long thread on vacuum systems that just occurred a few weeks ago. You might find some useful info in there.

 

http://wetpixel.com/forums/index.php?showtopic=49678&page=1

 

As to your question, I don't believe going the cheap route is a risky move. I only have the vacuum fitting and cap and don't feel there is any need for anything else. Just before the dive, I confirm the vacuum is still there by reconnecting the pump and gauge. If it is, you're all set.

Share this post


Link to post
Share on other sites

When going cheap, you get what you pay for; some times!

Share this post


Link to post
Share on other sites

Vivid Housings has tiny electronic indicators available for less than 75 Euro, with a switch and red and green LEDS to indicate whether the vacuum has been lost. I think most housings would have space for these where they can be seen from the outside.

Share this post


Link to post
Share on other sites

Do you think going the cheap route would leave me open to a disaster that could cost way more than $500?

 

Yes!

depending on your camera insider, but in case of a major flood you will destroy at least 1000$.

Is this amount (for most of us it will be much, much more) worth to play around with home built vacuum wannabees,

investing even if only 100$ in a home built vacuum leak tester?

If a home built system should work for some time, sooner or later you will get somehow sloppy in closing the housing and if

then the system fails it will lead to a disaster.

Well, you can get a camera insurance covering accidental floods, but in this case you don't need even a vacuum leak detector.

 

As i wrote in the other tread about the backscatter vacuum leak detector, i love my Hugyfot HugyCheck vacuum leak detector and built in water flood alarm and

if i should switch to another housing manufacturer the availability of this system will be one of the biggest point of the decision what manufacturer will sell me the housing.

Chris

 

 

 

 

Share this post


Link to post
Share on other sites

A balloon, tied off with the slightest puff of air in it could give a good indication of vacuum retention.

Good luck getting it through airport security ;)

Share this post


Link to post
Share on other sites

Vivid Housings has tiny electronic indicators available for less than 75 Euro, with a switch and red and green LEDS to indicate whether the vacuum has been lost. I think most housings would have space for these where they can be seen from the outside.

 

Thanks for that. Vivid Housing’s “Leak Sentinel” seems like a good option. The complete kit with flashing light indicator costs about the same as the basic “Housing Sentry” with no indicator. The vacuum fitting/indicator fits on top of the housing and it looks really nice. If they make a version that fits into a vacant control hole for my Ikelite then I might have to go with it:

http://www.vividhousings.com/leak-sentinel.php

 

However the “Sentinel” is a plastic fitting, and I worry that it might not be as durable and reliable as the “Sentry’s” simple metal fitting. Any thoughts on that?

 

In the meantime, I’ve already ordered a small digital barometer from China that costs less than $20. If it fits then I’d prefer that to flashing lights. In any case, I’ll also have a syringe, a condom, and Balrog’s ballon as backup. It’ll be beautiful.

 

For others who like to save money through gerry rigging, here are instructions for a simple homemade vacuum pump:

http://www.avs.org/chapters/nccavs/pdf/NCCAVS_EdCom_Manual_Vacuum_Pump_Made_From_a_Syringe.pdf

 

John McCracken

Share this post


Link to post
Share on other sites

Hello John,

 

Could you put the link to the chinese small digital barometer? I was also looking for one small enough...

Share this post


Link to post
Share on other sites

Hello John,

 

Could you put the link to the chinese small digital barometer? I was also looking for one small enough...

Hello David,

 

Sure, here is the link to the one I ordered:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=251147030734

 

You could Google "small barometer" or "small altimeter". If you're willing to spend a bit more money, you might find something better.

 

John

  • Like 1

Share this post


Link to post
Share on other sites

Hello John,

 

Could you put the link to the chinese small digital barometer? I was also looking for one small enough...

Sorry David,

 

The previous link didn't work. The one I ordered looks like this:

http://www.made-in-china.com/showroom/ljbetty/product-detailbqrQiMRoZIky/China-6-in-1-Multifunction-Digital-Altimeter-Compass-SR106-.html

 

You can find them on ebay. It may be junk but it didn't seem like much of a risk for the price. It just might be perfect.

Share this post


Link to post
Share on other sites

Hello John,

 

Could you put the link to the chinese small digital barometer? I was also looking for one small enough...

Hello David,

 

The cheap Chinese barometer was only good for telling the time inside my housing. I agree that a good barometer gives better information than the usual system of indicator lights - That was your thinking from an earlier thread. I eventually got a "Sun Altimeter/barometer 202 M", which works well for me.

 

A simple, well made valve from Miso at Vivid Housing cost 60 Euros. The barometer cost $60. and a vacuum pump that I devised cost less than $20 to make. I tested my housing, with the valve on and vacuum applied, in the dive store's pressure tank at a simulated depth of 50 meters. There was no leak, so I feel good about using this fitting on my next trip.

I have included a link to this custom made system from my Flickr account.

 

http://www.flickr.com/photos/pointymccracken/8723697445/in/set-72157633459277984/

 

John McCracken

Share this post


Link to post
Share on other sites

My previous post contained an unstable link. Here is a link to my photo sets on Flickr. The relevant set is titled "Cheap vacuum leak check". If you click on any of the thumbnails, you can read details about Miso's simple valve, the altimeter used as a vacuum indicator, and my home-made vacuum pump. I hope this works better:

 

http://www.flickr.com/photos/pointymccracken/sets/

 

John McCracken

Share this post


Link to post
Share on other sites

OK, I'm still a little confused by this whole concept. I understand that there are commercial versions that draw a vacuum as well, but wouldn't it make more sense to slightly pressurize the housing? That way, if there were a slight leak, you would be visually alerted by a stream of bubbles, rather than having the vacuum suck water INTO the housing. What am I missing? There must be an obvious reason why the commercial versions, as well as yours, draw a vacuum instead of pressurizing the housing.

Share this post


Link to post
Share on other sites

Well if you pull a vacuum on the inside of the housing, the outside air pressure will create a stronger seal via the housing o-ring than if you pressurize the housing. Too much pressure and you will try to push the back and front of the housing apart negating some of the sealing force.

Bill

Share this post


Link to post
Share on other sites

OK, thanks. That helps.

Share this post


Link to post
Share on other sites

It's testing for leaks using air. You test for leaks BEFORE entering the water. If you see a stream of bubbles from your housing while underwater, your camera is probably already toast!

Share this post


Link to post
Share on other sites

Sponsors

Advertisements



×
×
  • Create New...