[PSUBS-MAILIST] Depth Gage

Tue Sep 15 01:23:11 EDT 2015

OK, thanks Alec.It certainly looks good from every other aspect; & yes maybe somesmall directional LED light would do.Cheers Alan
      From: Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Tuesday, September 15, 2015 1:05 PM
 Subject: Re: [PSUBS-MAILIST] Depth Gage

Hi Alan,
My current gauge has no lighting at all, so I have to turn on the cabin lights to see it. I would certainly prefer it to stay on indefinitely, but on the other hand it lights up with the press of a button so I guess it's better than what I have now. If it turns out to be a pain, I guess I could rig some little lights strategically - it should be easier to place a few adhesive LED strips in the vicinity than to hack the gauge. There is also at least one other instrument I would like to see that has no lighting at all. I've ordered one, so let's see what it's like once in hand.

Best,
Alec
On Mon, Sep 14, 2015 at 7:01 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Alec,looks a good gauge; I am tempted to buy one :)It has an auto shut off after an hour, but this can be disengaged.The backlight goes out after 2 minutes which may be a nuisance, but as itworks off a small battery I guess this has to happen to preserve them.I would be interested to see if you think this is going to be a problem.A solution would be to wire the backlight LED to an external power sourceif you can get at it.Cheers Alan 
      From: Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Tuesday, September 15, 2015 1:02 AM
 Subject: Re: [PSUBS-MAILIST] Depth Gage

Coincidentally I just spent yesterday afternoon selecting one of those. I would normally prefer an analog gauge because I try to minimize electronics to maximize reliability. However, on a 1,000 foot sub the needle would barely move on shallower dives, so digital display is the only way to go. The accuracy of these instruments is measured as a percent of full scale, and a cheap one is accurate to 1% FS. For a thousand foot sub, that means the smallest depth change it could measure is 10 feet - not good! Well, let me rephrase that. I'm fine knowing my depth to within 10 feet, but what I really want to know if whether my depth is increasing or decreasing, and I'd like to know that before I've traveled 10 feet.
I settled on the Dwyer DPG-100, because it has this:
- 0.25% FS accuracy- Displays pressure directly in feet of water- Wetted elements are 316 SS- IP66 enclosure (waterproof to "hose-down" standard)- Lighted display- Battery powered, so no need to wire it into the sub power (battery life 2000 hrs)- Reasonably priced ($185)
It also records the max depth, hardly a necessity but cool for unmanned depth tests. For testing my K250 I just strapped a dive computer outside, but that wouldn't work for a test to over 1,000 feet.
Here is a link: https://www.dwyer-inst.com/PDF_files/A_34.pdf
If you want to go the Arduino or PLC route with a touch screen and all that, you can step up to the Dwyer DPG-200 because it transmits a process signal. The nice thing compared to the normal pressure transducers is if your Arduino, PLC, or display screen failed, you could still see the depth directly on the gauge. The DPG-200 also has high and low programmable alarms with NC and NO switches, so you could use it for example to automatically turn on your scrubber when going past ten feet, or to wake you up with a klaxon if you are going past your max depth.   However, it has cables coming out the back that make it a little less compact, and it needs an external power feed. Dwyer also offers low-cost screens that you can plug the DPG-200 depth gauge into directly without any processor.  
https://www.dwyer-inst.com/PDF_files/A34A_low.pdf

I opted for the DPG-100 because my focus is on simplicity, but depending on your priorities one or the other of these two should make a good instrument.

Best,
Alec

On Sun, Sep 13, 2015 at 8:56 PM, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 SSI technologies P51 family, but Honeywell MLH500PGL01G is about the same price and has better accuracy.  I use combination of arduino, raspberry pi, and processing for my project.  Seehttp://www.subdb.info/cgi/database/showvessel/albums/index.cgi?A=1320788990&B=1439139327&C=&D=Submarine%20Environment%20Monitor%20Software

 Jon

 On 9/13/2015 7:35 PM, Christopher Cave via Personal_Submersibles wrote:

  I'm looking to buy an electronic depth gauge. Any suggestions for a brand, software etc... 
  Thanks, Christopher  

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