I heard back from Emporia. After they kept trying to tell me how to download CSV files (which I knew), they finally understood my question was how to get 3 hours of 1 second data. it is already lame that 3 hours is all you can get, but at least I wanted that.
Their answer:
Mike,
The app has a time out every 20 min, which means if the app does not see any activity, it will close and average the seconds data to the minute.
If you just make sure you're not letting the app close in 20min, you will have seconds data in your CSV files.
We DO offer seconds resolution data, and it's available for 3 hours, as long as you keep the app opened!
In order to log 1 second data, you have to be constantly babysitting the app to keep that alive.
This is STUPID. Why have a data logger you have to basically monitor in real time?
In other words, if you are looking, they show you 1 second data. If you don't look, they throw it away and only save 1 minute data.
Think about the software effort it took to make this happen. Their server has to be aware if any app (mobile or web) is open, tell the sensor to send 1 second data only then, otherwise average data to 60 seconds, and store that data. This is bizarrely way more effort than simply storing the 1 second data directly.
These kinds of irrational design decisions are hugely frustrating.
Mike C.