My Detailed Initial In-Water Impressions of Garmin Mk3i

[Nick_Radov]

I have a mk3i now, moved to it from a Teric. (Haven't dove with it yet other than my pool to make sure it worked). I did read that they use two diff protocols with the T2 transmitter....one for above water and one for under. Wondering why the difference, and why you wouldn't use the same. My guess is the underwater may be a bit better, but maybe it uses more battery?

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[V1Rotate]

This seems like a clear illustration of the problem with having one technology for communicating cylinder pressure when on land and a different technology for doing the same underwater, and switching between the two automatically when the diver splashes.

I've said it before: If I cannot check it to make sure it's working before I get in the water, then I don't want it.

And having to do a complete reset of the computer sounds like a huge pain in the butt!

I should have clarified, this was my first dive with the Mk3i. I went through the pairing process with the Mk3i and T1 but I think the problem had something to do with the fact that my T1 transmitter was previously paired to a Mk2i. After the reset it worked fine on every dive. It wasn't a huge pain in the butt at all to reset the watch, you just select the reset function in the system menu and wait a few minutes for it to delete everything and return to factory settings, then you pair the watch and transmitter as if they are brand new out of the box. It took less than 10 minutes.

This was a one-time problem that was easily fixed, I wouldn't let this little hiccup deter you from trying a Garmin Mk3i, it's an excellent and reliable dive computer. I will still use my SPG for redundancy, but maybe I'll change my mind after another 100 dives or so, or maybe not.

Above water, the T1 uses bluetooth to transmit tank pressure to the Mk3i, underwater it uses an acoustic signal (basically sonar). Underwater I do hear a very faint little high-pitched chirp about every 20-30 seconds, but it's barely noticeable. On the boat as soon as I turn on my cylinder, the Mk3i tells me how much air pressure it has. It will even tell you when the CR123 battery in the transmitter is getting low so you can replace it before it dies.

 

[V1Rotate]

Yep. This is my big concern with the Garmin transmitter, though the T2 is actually a transceiver now. I don't so much mind that there are two protocols. I don't like that it's impossible to test the underwater protocol without being underwater. I wouldn't mind it at all if it were possible to force underwater mode to ensure that it's working prior to splashing. Since the T2 now receives as well as transmits, it would be great if that could be included.

I really like my Garmin and Shearwater dive computers. My Garmin is not air integrated due to the transmitter.

Which Garmin computer do you have?

 

[Jai Bar]

I have a mk3i now, moved to it from a Teric. (Haven't dove with it yet other than my pool to make sure it worked). I did read that they use two diff protocols with the T2 transmitter....one for above water and one for under. Wondering why the difference, and why you wouldn't use the same. My guess is the underwater may be a bit better, but maybe it uses more battery?

The reason is simple: the acoustic signal does not propagate in air at all, and the RF signal has a *very* limited range in water.

So, for good transmission in water they use ultrasound and for air they use radio frequency. Both are adequate solutions for the media through which they propagate.

The downside, as mentioned, is that testing the RF communication topside does not test whether the acoustic signal will work underwater. Does not test it at all, maybe except that the battery is ok on transmitter.

 

[Sevenrider860]

Above water, the T1 uses bluetooth to transmit tank pressure to the Mk3i, underwater it uses an acoustic signal (basically sonar). Underwater I do hear a very faint little high-pitched chirp about every 20-30 seconds, but it's barely noticeable. On the boat as soon as I turn on my cylinder, the Mk3i tells me how much air pressure it has. It will even tell you when the CR123 battery in the transmitter is getting low so you can replace it before it dies.

Not "technically" accurate. On the surface the T1 uses ANT to communicate with the Mk3i. ANT uses the 2.4GHz radio band, but it is not Bluetooth as they are different protocols. The T2 is interesting in that is supports ANT when communicating with the Descent computers, but will use Bluetooth to communicate with the Dive App for updates.

 

[Belzelbub]

Which Garmin computer do you have?

MK2s.

Not "technically" accurate. On the surface the T1 uses ANT to communicate with the Mk3i. ANT uses the 2.4GHz radio band, but it is not Bluetooth as they are different protocols.

Years ago, I overheard a dive instructor tell his students about his dive computer. I forget which one he had, but I remember him telling his students that the transmitter used Bluetooth to communicate his pressure. This was well before the T2 was introduced, and likely before the T1 was introduced, so no chance the transmitter even had Bluetooth capability.

 

[stuartv]

Reset is much quicker than sending in a Teric for a new battery ;-)

A reset on the boat, right before I'm about to splash, and now I need to re-setup all my settings is not nearly as convenient as picking a time when I'm not diving for a week and sending a Teric off for a new battery.

I should have clarified, this was my first dive with the Mk3i.

I understood that.

I went through the pairing process with the Mk3i and T1 but I think the problem had something to do with the fact that my T1 transmitter was previously paired to a Mk2i. After the reset it worked fine on every dive. It wasn't a huge pain in the butt at all to reset the watch, you just select the reset function in the system menu and wait a few minutes for it to delete everything and return to factory settings, then you pair the watch and transmitter as if they are brand new out of the box. It took less than 10 minutes.

You are not the first person I have read about that was getting a cylinder pressure reading before they splashed and then stopped getting one after they splashed.

Your reason may be different, but that just tells me that there are multiple ways it could "not work" - and you can't tell with any of them until you splash.

This was a one-time problem that was easily fixed, I wouldn't let this little hiccup deter you from trying a Garmin Mk3i, it's an excellent and reliable dive computer. I will still use my SPG for redundancy, but maybe I'll change my mind after another 100 dives or so, or maybe not.

I have been using AI for almost 10 years and do not use an SPG. I think it is a negative to have both. But, I concede that if I couldn't tell if my AI was going to be working after I splashed, I might have an SPG in addition.

Above water, the T1 uses bluetooth to transmit tank pressure to the Mk3i, underwater it uses an acoustic signal (basically sonar). Underwater I do hear a very faint little high-pitched chirp about every 20-30 seconds, but it's barely noticeable. On the boat as soon as I turn on my cylinder, the Mk3i tells me how much air pressure it has. It will even tell you when the CR123 battery in the transmitter is getting low so you can replace it before it dies.

Shearwater computers also tell you if their transmitter battery is getting low. Generally, you have plenty of battery left at that point to do a day's diving and then change the battery that evening. For whatever reason, however, they do not tell you any other battery status. You cannot, for example, check and see that the transmitter battery is at 50%. They only show a Low Battery warning when the transmitter battery is getting low and that is it.

 

[brsnow]

A reset on the boat, right before I'm about to splash, and now I need to re-setup all my settings is not nearly as convenient as picking a time when I'm not diving for a week and sending a Teric off for a new battery.





I understood that.



You are not the first person I have read about that was getting a cylinder pressure reading before they splashed and then stopped getting one after they splashed.

Your reason may be different, but that just tells me that there are multiple ways it could "not work" - and you can't tell with any of them until you splash.



I have been using AI for almost 10 years and do not use an SPG. I think it is a negative to have both. But, I concede that if I couldn't tell if my AI was going to be working after I splashed, I might have an SPG in addition.



Shearwater computers also tell you if their transmitter battery is getting low. Generally, you have plenty of battery left at that point to do a day's diving and then change the battery that evening. For whatever reason, however, they do not tell you any other battery status. You cannot, for example, check and see that the transmitter battery is at 50%. They only show a Low Battery warning when the transmitter battery is getting low and that is it.

There are plenty of other failures shared on SB with the Teric. I dive a perdix 2, but use Garmin for marine, hiking, mini for safety, have extensive experience with them and they are about as reliable as they come.

 

[Belzelbub]

Shearwater computers also tell you if their transmitter battery is getting low. Generally, you have plenty of battery left at that point to do a day's diving and then change the battery that evening. For whatever reason, however, they do not tell you any other battery status. You cannot, for example, check and see that the transmitter battery is at 50%. They only show a Low Battery warning when the transmitter battery is getting low and that is it.

I’ve never actually seen it myself, but I believe there are two levels of that alert. A Low Warning and a Critical Alert. This is true with all computers that are compatible with the PPS and Swift transmitters. The transmitter itself only sends three levels. This is imbedded in the data string sent. While Shearwater did develop their own transmitter, they also wanted to maintain compatibility, so I really don’t see that they had an option here as the data fields available would not allow real time percentages.

Some computers do allow you to check the transmitter battery level on demand. Others, like Shearwater include this information in the dive log.

 

[chrisjur]

Above water - Bluetooth and ANT ( 2.4 GHz radio frequency )
Under water - SubWave ( acoustic signal ) greater range

Exactly! Key reason being that Bluetooth do and ANT not transmit reliably underwater.