Faulty Vacuum Sensor

Forgive me if this has been brought up recently.  I am wondering how many photographers have had issues with faulty alarms with their  Sentinal vacuum alarm.    I never used one until I upgraded to a mirrorless camera and new housing.  The housing manufacturer sold the vacuum unit and installed it.  I have had a lot of false alarms where sensor would go red during a dive but no water got in housing.  

What procedure do you use when setting up the vacuum system?  I have seen reports from people having this trouble who tried to minimise the vacuum used by pumping until the light just went green.  I normally give 1-3 more full pumps once I get green on my Nauticam system.  Lots of people use the Leak sentinel system and seem to be very happy with it going by reports I've seen here on WP.

Like Chris, I add an extra couple of pumps once the light goes green.

An other possible issue is moving the housing into a much warmer or cooler location than the one where you installed the camera in the housing - or created the vacuum.

Depending on the model of Sentinel you have, that can sometimes create an issue. Models v4 and v5 have circuitry that compensates for temperature change but, on occasion, I have had false reds too. Scary!

I understand a v6 is on the horizon......

Aloha!   Thanks for fast responses.   I do give it a few extra pumps. I am pretty sure it is V4. I have put a moisture pack under camera tray for moisture and am aware and careful about temp changes.  I try to keep camera and housing at ambient temp, but on Liveaboards have gone from an a/c environment to the dingy, and then a boat ride to site.  I set ups fora dive the night before and do a vacuum check.  In the morning I hope for green light, and go diving.   Several times now the red light flashes in the morning indicating a leak.  When I open, I need to vent air and that tells me the housing did not leak air.    Several times while out on a day boat, the red light starts blinking.  I have aborted dives and checked housing to find it dry.

Sure sounds like you are doing all the right things, Douglas.

I've got the V5 and have had a few false alarms of late - including the same overnight and red in the morning as you've experienced; and, like you, having to vent to check the housing. I've put it down to temperature variation (I'm in the tropics) but that maybe me trying to excuse the gear!

I'd suggest dropping Miso an email and outlining what you are seeing and see what he says. He's very helpful.  

info@vividhousings.com

Let us know how you get on. It's always useful to build the knowledge base on these types of devices. 

Just because you vent air doesn't mean there was no leak, there could have been a slow leak in that time period, but hasn't lost all the vacuum yet.  I do all the same stuff with my Nauticam system and have not had any issues with false alarms - touch wood!.  You can't switch the Nauticam system off overnight and I've pumped down and left the housing overnight in the past as well as pumping down before heading off for a day's diving. 

Technically for a false alarm to occur due to temperature the absolute pressure must go up and the only way to make the pressure go up without adding air to the housing is for the housing to get hotter which increases the absolute pressure.  Absolute pressure refers to the pressure above absolute zero pressure or a perfect vacuum - it's what you use when calculating pressure changes due to temperature.  

Causes for an alarm could include first an air leak, then a temperature change and it would have to increase,  or an issue with the pressure sensor - it might itself be temperature sensitive.  It might also include how the circuit is programmed.  Typically you would need to reach a certain vacuum to switch the device over to monitoring mode then have to decide how much the pressure needs to increase before it triggers an alarm. 

I'm wondering if the issue might be the construction method for the leak sensor.  As I understand it the regular models are fully self contained inside the device you screw into the housing.  This would cool off faster than the housing itself and the sensor circuit would expect the pressure to drop but when it doesn't as the air inside the housing will cool more slowly it could trigger the alarm.  They also make a model with the circuitry inside the housing and this should not have that problem.  This would explain an alarm after jumping in the water but not the overnight alarm. 

Probably it is not the vacuum sensor, but the moisture alarm. I had similar problems repeatedly with two Nauticam housings (NA-EM1II and NA-EM5II). In my case it turned out to be the moisture alarm (see photo in the link below). I solved all the problems by making the moisture alarm less sensitive: I inserted an additional contact to bridge by clipping the yellow wire...

View archived post in: Nauticam vacuum leak system defective?

Wolfgang

I’ve had false alarms due to temperature when I had the housing in the sun or a car parked in the sun. I never had a false alarm during the dive. That would indicate to me that you might actually have a tiny leak or something or there is an actual problem with your vacuum. During the dive it can hardly be explained by temperature variation. 

As I understand it the Leak sentinel does not have a water alarm and normally the water alarm has a buzzer to distinguish it.  You test this out by testing the contacts with a damp finger.  

@hyp, I offered one way it could alarm due to temperature variation - it would require a latching alarm, which most of these devices seem to have.  The cuase could be lag between the sensor cooling off and the gas inside the housing cooling.

Aloha everyone, and thank you for your feedback.  I really appreciate it.  The housing has an audible moisture alarm and while I have heard it go off, my concern is about the intermittent red light flashing on the sentinel vacuum unit.  Maybe the sensor has an issue and I am getting false alarms. I went diving with housing yesterday and it did not leak but the red light flashed.  I did maintenance and put camera and lens inside.  The sentinel vacuum has held green for 24 hours. I am taking it diving tomorrow.  The irony is this is the first housing I've used in 28 years of underwater photography that has a vacuum alarm. I switched from Nexus when I got the Z7II, and the vacuum was part of the new system.

13 minutes ago, ChrisRoss said:

As I understand it the Leak sentinel does not have a water alarm and normally the water alarm has a buzzer to distinguish it.  You test this out by testing the contacts with a damp finger.  

Correct Chris, there is no water alarm on the Sentinel. It's vacuum leak only.

1 minute ago, mauidoug said:

Aloha everyone, and thank you for your feedback.  I really appreciate it.  The housing has an audible moisture alarm and while I have heard it go off, my concern is about the intermittent red light flashing on the sentinel vacuum unit.  Maybe the sensor has an issue and I am getting false alarms. I went diving with housing yesterday and it did not leak but the red light flashed.  I did maintenance and put camera and lens inside.  The sentinel vacuum has held green for 24 hours. I am taking it diving tomorrow.  The irony is this is the first housing I've used in 28 years of underwater photography that has a vacuum alarm. I switched from Nexus when I got the Z7II, and the vacuum was part of the new system.

Douglas, as I suggested earlier, drop Miso a line at Vivid. He's The Man. Outline the issue to him. 

Aloha, this is correct, the sentinel does not have an audio moisture alarm.   The audible alarm is separate.

Thank you Tim, I will do that. Mahalo!