Thanks for the info that’s good to know.
Nice work!
I ran one out to 12 days until a couple of days ago but it seemed like it was +/- 20-30 points from sensor readings rather than +/- 5-10 points like fresh sensors so I yanked it. I’ve never done arms as I can see that the whole sleep and lost signal problem would be a barrier.
Do you have the 640 @Buckley83 and is the range issue any better with them? Or maybe do you notice that they have to be inconveniently close? This has always been somewhat annoying but seems like it would be an easy fix! Thanks fo rthe interesting experiments @phoenixbound but, as long as I have sensors, I’m probably just gonna keep to 6-7 days/ sensor…
Hey,
Yes I have the 640g. Only time I’ve had an issue with lost signal is when I’m in the bath and the water is attenuating the signal.
I can actually leave the 640g up to 5-10m away from me and it will keep the signal.
I have noticed that the signa;l drops if my phone on bluetooth and when I use a bluetooth speaker or have several wireless/bluetooth things connected in the vicinity I can get a lost signal!
So how do I learn about ISIG???
It depends. You can download your pump’s data using a PC (or Mac?) and Medtronic’s “Carelink” web utility and then create a Data Table report which will include this value and others.
How you display it on the pump I think varies depending on which Medtronic pump are you using. Which pump do you use?
Interference.
Medtronic switched the frequency used by their newer CGM transmitter, the Guardian Link 2, to connect to the 640G. I have read that while the MiniLink transmitter is ~900 MHz band the newer Guardian 2 uses the 2.4GHz band (and the IEEE 802.15.4 standard?).
Other things that can interfere with a 2.4 signal (if you are close enough) are probably (running) microwave ovens and 2.4GHz cordless phones (not a mobile) and baby monitors.
If the pump is “close enough” to the transmitter it should side step the problem. But since the signal from the Guardian 2 is a weak one, my guess is that it doesn’t take a lot of noise to make it hard for the pump to talk to the transmitter.
Call the helpline! I’ve gotten all sorts of info from them, as well as other, local sources.
Just got 11 days from an enlite, pretty happy with that!
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Is it still going?
No died today with error “Sensor not working properly. Insert new sensor”.
Got the error message at 19:13, just noticed in the history that the sensor was still reporting an normal ISIG number after the message so maybe I should have left it in and tried resetting.
had you gotten 2 cal errors, per chance, as that will tell you to change the sensor
No didn’t have any cal errors with this one!
My guess is that this message is new to the 640G. For one thing, I don’t recall ever getting any message on my Paradigm 723 which had that many words in it. The more typical alert for the older, smaller display is stuff like “LOW RESERVOIR”, “METER BG NOW” or the infamous “WEAK SIGNAL”. Something around 12 or so capital letters in length.
I also don’t recall seeing the wording of the message. My wild arse guess would be that this message is a consequence of either updated pump firmware or possibly of the alleged new “diagnostics” supposedly embedded into the new (to anyone in the US) Guardian Link 2 CGM transmitter. Still wondering what, if anything, is up about that.
I suppose. The 6.4 mmol/L BG is around 115.2 mg/dl, correct? That gives a U.S. cal factor (meter BG/ISIG) of ~6.8. While it’s not horrible, I tend to think anything much beyond 5.5 to 6.0 is a potential sign that a sensors is dying. I much prefer it to be under 4, if possible, but at least in the range of 4 to 5.5.
My current Enlite, which I’m just about to pull and replace after only around 5 days, is using a Calibration Factor of 7.559. (I use CareLink to download the pump and generate the Data Table report to see what calibration values the pump is actually calculating & using.)
Technically Medtronic would probably insist it is still working. My personal feeling is that usually when CFs head into this territory accuracy starts to suffer.
In my case, the SGs (Sensor Glucoses) are likely to start differing noticeably from the BGs (Blood Glucoses) and I won’t feel I can trust the sensor. More to the point, when my BG swings … and it does do this … the sensor will be less likely to pick up on it. The SG may be showing something like 130 mg/dl (7.2 ?) while a meter BG will come in as 269 (14.9?).
Just curious, what ratio does Medtronic encourage the folk outside the US to look at to get a rough take on the health of an Enlite? My guess is they use something different to avoid ending up with a number between 0 and 1. Or perhaps the folk outside the U.S. just aren’t as uncomfortable working with fractional values? 
Wouldn’t it be between 3/18 and 8.3/18?
Close. The cal factor range of 3 to 8 would be more like 3/18 (~0.167) to 8/18 (~0.444) if the BG was in mmol/L instead of mg/dl.
If you prefer the range 3 to 8 1/3 then it would be something like 9/54 to 25/54, which in decimal would be between (approximately) 0.167 to 0.463.
And thus we have an illustration of one of the probable reasons why the decimal system was adopted.
Can you actually see a help desk suggesting to people to find out if their cal factor is between 0.167 to 0.463? 
Well, perhaps, if the folks outside the U.S. really are that much better with arithmetic … 
But I think it’s more likely that Medtronic tries to come at it from a slightly different but equivalent enough direction. BWTHDIK? Which is why I asked.
Bear in mind many MM patients have NO IDEA what ISIG is. I went to a meeting about 6 months ago and 2 out of 3 people at the meeting didn’t know squat about ISIG’s, so obviously they also have no idea about CAL FACTORS.
True. But in spite of that, I have had the MM help desk describe how to calculate the cal factor as part of whatever checklist they step through during a call asking about sensor wonkiness. They have also read off that absurd (to me) range which goes all the way up 8 or 9, presumably from the same checklist.
I’m just wondering if the MM help line outside the U.S. has a similar checklist and, if so, what do they use instead of the cal factor as we, in the U.S., know it?
Thanks for the info John. I have been watching my ISIG values for the last few day and the US cal factor seems to be pretty consistently sitting around the 5.9 mark so close to the values you are getting.
I’m in Australia and when I call the helpline I get transferred to someone in the US so maybe we share the same helpline staff! I have only called once about sensor issues and they never mentioned ISIG, they just asked some basic questions then sent me a new sensor.
Crud, I only got 10 days from the last sensor. 
My guess is that calls from outside the U.S. are handled differently than calls originating inside the U.S. But testing that assumption would probably involve comparing notes on what happened during the calls and it would all still just be anecdotal i.e. inconclusive.
It’s been a while since I called but one thing I remember is that the first thing I am asked after they have gotten my ident info & looked up my entry in their database is what my last meter BG (Blood Glucose) was. My experience has been that they always ask that. Since it seemed to be completely out of context and thus made no sense to me, I think I asked once and IIRC I was told they do it because the U.S. FDA wants it in the call logs.
If I am talking with them about a glucose sensor problem they have a checklist they walk through. If they have never discussed ISIG’s when you called about a sensor then perhaps they have a different checklist? Of course, it could also just be that the nature of your problem let them bypass their checklist.
Have called the help line to report bad or otherwise wonky performance from an Enlite? Those are the sort of calls I think I remember them dragging out the talk about determining what the most recent “Calibration Factor” was and telling me it should be between 3 and 9 (or some other number which always seems too large to me based on my personal experience).
On the other hand, if you called because the pump gave you a sensor error message then they may just replace the sensor and not try to do any problem isolation? Maybe? Perhaps?