Does Instinct 2 Standard Edition support HRV measurement at night in milliseconds? Is it RMSSD?

9964163 said:

But does the watch measure HRV at nigh (automatically) and display it in milliseconds? Or displayed in milliseconds in the Connect app.

Yes, it does. Check out the Sleep Timeline Metrics chart in Garmin Connect, and enable the option Overnight HRV under the graph.

9964163 said:

What HRV metric is used? Is it RMSSD (Root Mean Square of Successive Differences)?

AFAIK, Garmin does not specify it in their documentation, but from the context of the article at What is the Health Snapshot Feature on My Garmin Watch? | Garmin Customer Support it appears to be indeed RMSSD. The Health Snapshot measures both the RMSSD and SDRR values.

Thank you! Will buy one today now that I am sure that it has the HRV I want.