Ok, read through all the SD card info on this site (google site:moosh.im helps a lot).

Smaller cards work better it seems, so I found a 32 MB card in my junk drawer, and it works pretty well. No more long light, and logging works as expected. There’s some odd fields in the data file: RMS INT Temp[C]
comes out at -271.53062, oddly close to absolute zero (maybe the AC temperature component expressed in Kelvin?), but otherwise it works.

Just for future reference – a Sandisk Extreme 16 GB micro SDHC-I only worked once for me, then refused to write anything. A Sandisk Transflash 32 MB (that I found in a parking garage years ago) works fine though. I’d love to know the exact model SD card the developers are using, and buy some of those. So far so good; I think I should get around two weeks of logging at 1 sample /s on a 32 MB card.

I’m hoping to use my Mooshimeter to monitor the O2 sensor on my motorcycle as I ride around a bit and see what the fuel injection computer is up to. Just the sort of thing that would be difficult with a regular multimeter.

Also, I’ve been keeping the Mooshimeter in my backpack as my travel multimeter, and with its always on bluetooth link, I can do an avalanche transceiver style search pattern for my backpack using the signal strength displayed on the phone app. Pretty handy, that means I can find my (perhaps lost) backpack in a building within a roughly 150 foot radius. Might have to stick a bluetooth dongle in my wallet too… :)