I got a couple of the ???'s on my G4 that happened to resolve themselves in three hours or less, but during the most recent occurence, I actually called tech support. I was told to just wait (which I wasn't happy about, but it did eventually start functioning again) and that it is not idicative of a real a sensor/transmitter problem unless it doesn't resolve itself within three hours. The tech went back to a statement I made that I got the ??? error after running/exercising and that it appeared to follow an out of range error, even though the receiver was never more than 6 inches from the transmitter. The Tech said that based on feedback they are getting, they believe that the issue may be the result of static charges generated by the transmitter rubbing against a synthetic shirt. The the two times that I recall getting ???'s were after exercising in the drizzle and wearing a medium weight dri fit shirt that was a bit clingy because it was damp, once over a compression shirt once not.

I was told that the proposed solution at the moment is to wear cotton shirts against the transmitter. I would think that this could also be an issue with other types of shirts or even dresses, too. Just wondering if it seems to explain some of the issues other are having. He said that once they have a better understanding of what is happening, they would add it to the FAQs section with any solution they may come up with. Don't Europeans exercise, too? Haven't they been using it for a year or so already?

Just thought it was worth putting it out there.

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Thanks for sharing this. I've been using the G4 for about 6 weeks and I've had a few ??? periods, all of which resolved favorably. I wear a synthetic long sleeve t-shirt to bed. I'll pay attention to any ??? periods coincident with wearing this synthetic t-shirt.

I get the impression that a lot of Europeans do not have easy access to this technology or have to pay out of pocket for it. I wonder how many Europeans have the G4.

Thanks for sharing, I am so relieved to read this. Just yesterday went running (in a quick-dry synthetic shirt) and got the identical pattern: out-of-range followed by ???. I was trying to figure out whether the culprit was proximity to my mp3 player headphone wires, the receiver getting too cold, etc.; couldn't make sense of it. This static charge interference mechanism explains it.

OK, I went running again today, this time covering the G4 transmitter with a large Band-Aid prior to running, my reasoning being that the bandage (although itself synthetic) would prevent my synthetic shirt from rubbing against the transmitter shell itself (which I noticed has a matte, textured finish as opposed to a glossy finish as on the Seven Plus), thereby preventing static charge buildup in the transmitter shell.

It didn't work. 10 or so minutes into the run, I was again getting the "out of range" icon. It did seem to reduce the severity of the problem, in the sense that once the sensor came back online about 20 minutes after I ended my run, there was no "???" status, just accurate readings. But nonetheless, during my run the transmitter was nonfunctional.

Makes me wonder whether (A) the bandage itself carried or transmitted to the shell sufficient charge so as to interfere with transmission; or (B) the problem is not with static charge being induced in the transmitter shell at all, but instead results from charge building up in the clothing itself such that the field associated with the shirt as a whole is what is interfering with the transmission, which seems much more likely. Tomorrow I'll run with a cotton pad covering the transmitter, which should effectively insulate the shell from any direct static effect. If it still stops working, then the problem is more likely (B). Which would suck if true.

This should be more than a little embarrassing for Dexcom. Didn't they field-test the device under various conditions of use? Didn't anyone testing the device do something that all diabetics should do, exercise, while wearing, you know, modern exercise clothes? In San Diego??

Success. I folded about 18 inches of small (2 inches wide) 100% cotton bandage five or six times to make a pad and secured it over the G4 transmitter with medical tape during exercise. Both cotton bandage and tape were purchased at my local drug store. I have done two 7mi runs since, without losing signal, wearing synthetic exercise clothing.

This may indicate that the loss of signal is related to static charge buildup in the transmitter shell itself from friction with the synthetic clothing.

If so, the fix could be relatively simple, involving Dexcom glossing or applying a coating to the transmitter shell that is refractory to static charge buildup in this situation, or, a more involved fix might require introducing some sort of insulation into the transmitter design due to the increased presence of sensitive components in the G4 transmitter.

I hope they can finalize whatever redesign needs to happen and can simply begin to exchange the current transmitters for any redesigned ones when the current crop are returned after battery depletion in 6-12 months. Exercising with synthetic, quick-dry clothing that one can take into the shower and hang up is extremely convenient, and when one lives with others, nearly the only way to go. Spouses, friends and roommates tend to dislike the buildup of used cotton exercise clothes...

Forwarding this thread to Dexcom.

would skintight cloting be better than loose clothing rubbing back and forth? my daughter is a dancer

Not sure. The synthetic shirts I run in are relatively tight, though not quite "skintight" like a leotard. At a guess, I'd say that it might take longer to lose signal, dependent on the intensity of the routine, but it could still happen. She might want to bring along a backup cotton shirt or cotton pad+tape to the first rehearsal just in case.

Thanks for the solution (although I agree that it's not one that users should have to figure out). I'm new to Dexcom, having just started my 3rd sensor. I had identical sensor behavior that you describe while out on bike rides both days this past weekend. It was made even worse by the fact that it seems to take time for the charge to dissipate so I had no connection for about and hour and a half after a 2 hour ride. Since I'm still within the 30 day return window, I'm considering whether this is a "deal breaker". I wish I could try the Minimed Enlite sensors before I make the commitment to return the G4. I've never had this kind of behavior between my Minimed pump and sensor in 3+ years of riding with the same types of clothing that haved caused so much trouble with the G4 sensor.

I tried the gauze covering solution while bike riding this past weekend and am pleased to report that it worked well. I did not lose the signal to the G4 even momentarily. Thanks for the suggestion.

Hi, I am in UK and have been using the G4 since July. I find the main cause of ??? for me is having showers after week one. I now try to protect the transmitter from the full force of water during my daily showers to try to prevent it getting utterly drenched which seems to help as I'm getting fewer ???. So I think it's a moisture issue: do synthetic shirts trap moisture on the skin whilst cotton ones soak it up?

hmmm, my daughter is a dancer, and she'll have the transmitter under a dance leodtard mostly, wonder how that will go?

I'm using Dexom 4 for the second time and in the end of the second week for the second sensor I also started to get quite a lot ???.

I have been exercising with synthetic fabrics. When I used Dexcom 4 the first time, the sensor was placed higher up on my left arm which made the synthetic to cover the sensor while training. I did not start to get the ??? until the fourth week and mainly during nights.
Now the second time I use the sensor, it's on my right arm but little bit lower on the arm than on the left arm. My synthetic shirt does not cover it while exercising.
But I get the ??? mostly at nights.
My feeling is that I should place it more near my shoulder and more outwards. I remember that my nurse helped me to find the right place on the arm, therefore I wonder, could that be also one reason, the place on the arm?

The other thing I noticed this second time, is that my Animas many times do not show any arrows.

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