James,

OK, I figured it out. The cards not working had been set up as logical partitions not primary. When I changed them to primary partitions they now work. This happened as these cards had been used on my Raspberry Pi and when I went to use them for the Mooshimeter I used EaseUS to clean them out and created the FAT32 logical partition by mistake. My error.

I still find it interesting the meter seems to be in a one second logging function based on the LED flashes when there is no card or if it is formatted as logical.

In any case mystery now solved and I’ll get back to doing some logging with confidence.

Thanks,
Mark