How to test a Medtronic MiniLink CGM transmitter & why you might want to

I spent not quite an hour with Medtronic’s Help Line earlier today futzing with them about my MiniLink transmitter. When we walked through the complete test script (below) the rep concluded that my MiniLink was defective and needed to be replaced.

What was interesting to me was up until that point I had thought my transmitter was still working just fine. Gosh, So maybe that is why my last few Enlite sensors all seemed to have been manufactured in Wonkytown. :open_mouth: :blush:

For whatever it’s worth, I have posted below my understanding of the MinkLink test script which the rep walked me through. These steps can also be found in the (large) user guide for either the Paradigm Revel or 530G pumps.

However, I did not find this complete set of steps in the user guide which came with my MiniLink. The only instructions there for using the test plug was to connect the test plug to the transmitter and then verify the green light flashed. In my case, that simply was not enough to tell whether the transmitter was working correctly.

###Testing the MiniLink CGM transmitter using the test plug.

  1. Visually inspect the connector bridge inside of the connection port of the MiniLink for damage.
    Speculation: I really have no idea what a damaged connector bridge might look like, but FWIW this is the first thing the Help Line’s script asks you to do.

  2. Turn the Sensor feature of the pump OFF.
    I was told it should be off for at least 30 seconds before turning it back on in step 6 below.

  3. Plug the MiniLink transmitter into the charger and charge it for at least 1 minute.
    Speculation: I am not sure if the point of this step is to ensure the transmitter has enough of a charge to test it or to ensure the internal logic in the transmitter has been reset. Possibly both?

  4. Very gently and carefully connect the test plug to the transmitter until the flexible side arms of the tester click into the notches on both sides of the transmitter.

  5. Within 20 seconds after connecting the tester, the green light on the transmitter should flash for about 10 seconds. Verify that there are 6 flashes spaced approximately two seconds apart in about 10 seconds.   :bulb:— 2 sec —:bulb:— 2 sec —:bulb:— 2 sec —:bulb:— 2 sec —:bulb:— 2 sec —:bulb:

  6. Turn the Sensor feature of the pump ON and then perform RECONNECT OLD SENSOR to establish the link between the pump and MiniLink. The connection icon on the pump screen will change from to to indicate that the transmitter and the pump have connected.

  7. Within the next seven to eight minutes, go to the SENSOR STATUS screen by pressing “Escape” three times starting at the main pump screen. Find the Sensor ISIG value. The sensor ISIG value on the status screen should be between 24.00–29.00 nA. This range of ISIG values means that the transmitter electronics are working properly.
    Note: The test range is also printed (molded) into the plastic body of the test plug.
    If instead you see a Sensor ISIG value that is less than 24.00 nA or more than 29.00 nA, then either the MiniLink is bollocked up or possibly you did the test wrong. Either way, contact Medtronic’s HelpLine and let them walk you through the test again to find out if Medtronic thinks you need to replace your CGM transmitter.

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####Why you might want to go to the trouble of doing the tedious test described above.

As I stated above, before I performed this test I thought my CGM transmitter was working fine. I was unhappy with the way my sensors seemed to be working within the last month or two, but I assumed that was purely a sensor problem. The transmitter held a charge, the green lights flashed when they were supposed to, so I thought everything was fine. What a silly goose I can be. :flushed:

I first became aware of this “extended edition” of the test instructions back at the beginning of October. Back then I had called the HelpLine because I thought the transmitter battery might be going bad. My transmitter warranty expiration date was 13 November 2015 so back in October I wanted to see if the transmitter could be replaced under warranty. But the transmitter passed the extended tests at that time so I slogged on with it.

Then yesterday (Wednesday) I was in the process of inserting a new sensor after the previous one had gone wonky after only four days and I thought … what the heck? So I ran the MiniLink “extended” test script as I recalled it and the status screen showed a Sensor ISIG of 111.46. Say what?

So after trying it on my own another time or two I called the HelpLine and went through the steps from their script and after the RECONNECT OLD SENSOR I saw test plug ISIGs over the next 20 minutes of 76.76, 56.16, 124.86 and 52.4. The verdict of the customer rep was “It’s (brain) dead, Jim.” :disappointed_relieved:

The above is my long-winded way of saying that as you approach the warranty expiration date for your transmitter, you might want to run the extended test periodically just in case your transmitter also decides to take a silent trip to Wonkyville as mine appears to have done.

At this point the HelpLine rep & I went back and forth a few times about whether Medtronic would do a “complimentary replacement” of my transmitter since it had died so close to the expiration date on record. The rep was willing to do it, but her supervisor vetoed it.

Fortunately I remembered to bring up the fact that while Medtronic had shipped me the MiniLink on November 13, I did not actually start using it until I was trained on November 26 of last year. That turned out to be the exact right thing to bring up.

The rep said if the training date could be confirmed then Medtronic would adjust the warranty date to start then. I forwarded her an email I had from my trainer setting up the training, and, poof!, I was now (sorta) within the warranty period (by 1 day?). Medtronic is sending me a warranty replacement transmitter by UPS Next Day AIr. Hopefully I will have it by Friday and get back to using CGM.

Why is it after finishing one of these marathon Medtronic HelpLine calls I often feel like I’ve just lived through an episode of Twilight Zone? I keep wondering what Serling’s “hidden in plain sight” moral aphorism was supposed to be. :smirk:

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I’ve had this exact situation happen to me before.
I paid to replace the transmitter. The thing I dislike about the whole situation is that the transmitters warranty is far less than the pump which is understand but still irritates me. :angry:
My transmitter was acting weird too but I suspected something was up with it.
That’s really cool they adjusted the warranty date to your training date. Technically you don’t wear it until then.


Well, in my case I did not suspect the transmitter. I felt it was strange that I seemed to be having more frequent occurrences of “sorta wonky, but then again maybe not” problems. But I thought it was an Enlite sensor problem, not the transmitter failing. I mostly went through the extended transmitter test because (1) I was at the 1 year warranty expiration date and (2) I tend toward the OCD end of the scale so doing diagnostics feels “right” to me.

But when I did the transmitter test I fully expected that it would check out to be still working fine. I certainly did not expect to find anything wrong with it. Which is why I figured it was worth posting about this.

I personally don’t expect the transmitter warranty to match the pump warranty mostly because I certainly don’t expect the rechargeable lithium battery in the MiniLink to last for four years. But the other surprising to me aspect of this is that some other aspect of the MiniLink transmitter electronics has a limited lifetime. I certainly never would have expected that to be the case. I don’t expect low power electronics to wear out. I really wonder what the heck is inside the transmitter which eventually “failed”.

Oh, well. My old transmitter will be returned to Medtronic when I get the new one so not going to be trying to open it up to look at the innards. :wink:

Do you happen to remember roughly just how much the replacement MiniLink cost you? I’m just curious mostly because Medtronic seems to take care to not make info like this easily accessible on the web. Or at least my skills with Google are not sufficient to locate it. :disappointed:

The mini link transmitter is $500. Ouch!

How much is the Dexcom transmitter?

It depends.

I just bought 2 G5 transmitters, expected to last 6 months. These two G5 transmitters take the place of one G4 transmitter. Dexcom billed my insurance for $823. The insurance adjusted the total price to $399.75. If memory serves me, this was the price of one G4 transmitter.

I am guessing that this is an “after insurance adjustment” price, yes? Hope you did not pay all or even most of it yourself. :frowning:

It could always be worse. I had convinced myself from Googling that the price charged those with little/less leverage might around $1000. Glad to hear it is likely not. Still $500 for technology which may not have changed much, if at all, since 2007 is, well, “nice work if you can get it”, no? :open_mouth: