Replies to This Discussion

Permalink Reply by Lorraine on May 31, 2012 at 5:46pm

Yes. I see it often, particularly when Caleb is asleep when it starts. It has always come back for us.

Permalink Reply by Jack's Mom on June 1, 2012 at 6:01am

How long does it take yours to come back in this situation? I gave it a half hour and gave up. Usually I wait about three hours, but was uncertain because it was a brand new site i.e. I thought a new site that immediately came up ??? might be hopeless.

Permalink Reply by Colleen in NH on May 31, 2012 at 7:38pm

Happens to me, frequently (and I'm a lot older than your son).
I usually try to give it several more hours. Sometimes it works and sometimes I give up and insert a new one. It's frustrating.
It's hard to be patient, though...

Permalink Reply by Jack's Mom on June 1, 2012 at 6:02am

Good to know - I will try and wait next time. Diabetes does force us to be more patient people.

Permalink Reply by Lorraine on June 1, 2012 at 7:47am

Very true!

Permalink Reply by jims on June 1, 2012 at 10:31am

I have seen all this nonsense and I decided to agressively checkout.

When I am in low RF interferor environment, it rarely happens - if ever. In a high noise environment it happens far too often.

I used to think sensor bad - not so.

Typically, I would pur receiver in fridge to force disconnect or in trunk of car - or wrap with aluminum foil temporarily.

I would leave environment in when problem occurred and watch in 1/2 hour or less receiver would link back up to MY transmitter and I would see in the quiet environment, system would perform well/correct with proper readings and/or I could easily do 2 hour calibration in quiet environment without interference and system would start up correctly.

One sequence of events I would see while operating, the receiver display line would start falling fast for no apparent reason ( fingerprick - static on trend) , then when I walked outside, I would see my receiver disconnect and when it reconnected, the dreaded ??? would appear because the receiver had been fooled into thinking there had been an excessive value change - bad sensor.

Strangely, if I caught at beginning of cycle before it had dropped too far and walked outside fast in quiet space, correct readings would show up and system continued working fine.

Many times afte this curious exercise and getting back up, I would find nothing wrong with sensor/receiver pair and worked just fine.

As for what is happening, I do not know.

One aspect of this is that receiver/sensor pair always work in car and out with the jack rabbits in Mohave wild open space.

All my trouble is in my condo and in my trailor in big pine which is extremely disconcerting.

Is someone hacking me - dunno. How many back door interfaces are on this technology - dunno. Is there also a blue tooth 11/52 meg capability left on.

One issue is that interfering RF can cause excessive interrupts in tiny micro.

Micro overflows stack, looses data and reloads incorrect sensor data after interrupt causing false ??? error indication.

So far I have successfully stopping this nonsense by causing disconnect on receiver and move to quiet RF environment or in car and repeatedly watch system recover and put out rational in spec readings.

Notwith standing my above comments, lately I have watched excusrsions on my receiver/sensor pair that completely violated my normal patterns, speed of body chemical process, fingerprick readings during offending behavior as though I was watching a movie being played out on my receiver as somehow my trasmitter was being overridden. This only ever occurred in my condo/trailor system.

In the end ,my data has been specific and clear that in quiet RF environment without any other interferors, the system has been working properly and saving me grief making my life better.

In my condo and trailor, this product has taken over my life watching and checking bizarre behaviour that should not be happening and validating with extra fingerprick readings.!

Permalink Reply by jims on June 2, 2012 at 10:31pm

Some simple advice from actual traping of cell phone causing ??? on dexcom.

I had case where I had my solid state rf field meter had signal trap running in my trailor that snapped my cell phone ( on but not calling)
attempting to reach cell tower and immediatly caused dexcom to flag ??? while doing the thwo hour initialization.

I left trailor for quiet zone sans cell phone and re ran 2 hours without incident.

My guess is that keep cell phones away and turned off - stuffed in fridge during this initialization process to reduce opportunity for (false) ??? error traping on dexcom. Even though not on call, cell phone sits there interrogating possible cell sites or talking to them while turned on.

Permalink Reply by Djinn on June 7, 2012 at 11:29am

Aha, a light bulb has just gone on above my head. I had my cell in the same little bag as my receiver last week - this seemed like a wonderfully efficient development given the increasing number of fiddly high-tech toys I have to carry around - but I kept getting ???. So I took the cell out and put it back in my purse, and the ??? went away. Hadn't thought about it since, but hey, thank you so much for the insight.

Permalink Reply by Korrie on June 3, 2012 at 4:03pm

I too am way older than Jack, but I find that my Dex and I do so much better if I insert and wait between 4 to 6 hours (like overnight) before starting a new sensor. I tend to have the ??? otherwise - either the Dex will not allow me to enter start up sugars at the 2 hour time frame or I get ??? within the first few hours of use the first day. I also tend to think that if my sugars are rapidly changing when the Dex is getting close to or has ask for the start up sugars, then I tend to get a ??? instead of trending arrows. So I almost always now insert at bedtime and start sensor in the morning - new sensors only. The second week restarts I just hit go and wait for the blood sugar prompt.

Permalink Reply by Jack's Mom on June 3, 2012 at 6:47pm

Yes, we have gotten a lot of ??? in the first 12-24 hours after a new site insertion. However, it's usually when he's down for a nap or at night - he sleeps 15 hours a day - and we have to put his sensor on the other side of a wall or above his room so we can read it without having to go into his room constantly. Of course the data gets a little muddled going through walls and ceilings / floors which was why I always assumed we got the ???. I can not WAIT until the new Dexcom gets here that can go 30 feet!

However, it's very reassuring to know that if I get ??? on startup I should just wait and it will probably come online. And I can go back to sleep.

We go in there so much as it is he's starting to yell at us in his sleep "Dark! Night Night! No beep beep (he's on an omnipod which beeps for boluses). What are you doing in heeeeeere ....." all without waking up.

Permalink Reply by jims on June 3, 2012 at 9:49pm

I am unhappy with the aspects of the ???. I believe that was originally there to catch readings out of range or defective - ie interstitial tissue issues. That is partly true. I suspect and agree.

It also seems to catche some very suspicious other goofy values having nothing to do with sensor readings and more to do with excessive interrupts and improperly controlled and carefully scheduled machine operation that prevents stack overflow and erroneous data sneaking into the process.

One of the classic ways to shut down an old DEC computer was to put excessive interrupts on the interrupt line from an open serial io line feeding a serial line input line and watch the vax brought to its knees with excessive interrupts.

Permalink Reply by Jack's Mom on June 5, 2012 at 5:24pm

VAX. Wow, that took me back. I am a software engineer by trade.

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