I have two PVR 250 cards in my KnoppMyth box. How do I determine/specify which one's remote sensor is the one used by myth?

I used the trial and error method. I plugged the sensor into 1 card tried the remote, when it did not work I switched the sensor to the other card (did this without shutting down) and it worked there.

Problem is neither one is working! Makes troubleshooting twice as difficult (or at least, makes it take twice as long).

Usually the first one, aka /dev/vide0. At least on my motherboard that's the one in the slot closer to the CPU.

To be sure you can use the cards serial numbers listed in the log files. I don't remember if the serial number is printed on the sticker, but you can always pull one card, boot, note the serial number listed for tveeprom in the logs, put the other card back in, and then you'll know which one is which.