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bobbyjobling

Development Team Member
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Posts: 211
 #1 
Hi Roger,
when I use my Garmin 1000 or PerfPRO software to track my live THb & SmO2 I get a THb value of 0 when my SmO2 saturates down to 0% it then eventually reads OK when SmO2 is > than 0%. However the data recorded in the Moxy device the THb values are consistent see images. This is unlikely to be a signal problem as it happens specifically when SmO2 hits 0%. I'm just wondering if the calculation fails when presented with a 0 value. 

FW Part Number: 2000195 v1.1.6
LUT Part Number: SN0157 v0.0.4

 THb error.png   

THb moxy csv.jpg 

Roger

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Posts: 252
 #2 
This issue is caused by going off of the edge of the lookup table that the device uses to calculate measurements.  The Moxy calibration table covers the SmO2 range from 0% to 100%.  However, the measurement system isn't perfect.  Sometimes it measures a few percent low, sometimes a few percent high.

If it measures a little bit low when you are very near the bottom of the range, it goes off the edge.  Then it sends out a 0 SmO2 and 0 THb value.

We're working on some firmware updates right now.  I think we can make the sensor handle this situation a bit more gracefully.  I think it still calculates a reasonable THb even if the SmO2 goes off the edge so we can probably just use that.

You may be able to avoid the problem by changing the sensor position slightly.  I often find that measuring a bit higher on the leg (further from the knee) can help.  The muscle is more homogeneous near the middle because there are less tendons.
bobbyjobling

Development Team Member
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Posts: 211
 #3 
Thanks for info, looking forward to the Firmware update[smile]
runner

Development Team Member
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Posts: 56
 #4 
Has there been a firmware upgrade to address this issue?
I am experiencing the same problem with Garmin Fenix 3.
fellrnr

Development Team Member
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Posts: 8
 #5 
I'm also seeing regular readings of zero for both values on a Fenix 5X with the Moxy set to the SmO2 profile. 
bobbyjobling

Development Team Member
Registered:
Posts: 211
 #6 
At the moment the only solution is to move the sensor to a location with a higher percentage of fat under the MOXY sensor.
For example, on my VL I was able to eliminate the problem by moving the sensor 20mm towards the RF muscle. Note that SmO2 reading will be higher throughout the session so you may need to reevalute your base values and trends.
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