I had a cartridge that I thought had stopped working and wanted to know for sure but THCScientific hasn't released their testing tool yet.
For the Omicron to work, electricity flows from the battery through the cartridge completing a simple circuit. Therefore all we need is a continuity tester to see whether a cartridge is good or bad.
For you DIY types that have a volt meter that also measures resistance (ohms), you can test your cartridges (both new and used) to see if they are working.
Here's the meter I used, iirc, I got it for about 15 bucks at Lowes.
The ranges on my meter for resistance are 200, 2k, 20k and 200k.
I set the meter at 200.
Here is an incomplete circuit (probes not touching), and it reads 1 on the meter.
Here are the probes being touched together, the meter measures a resistance 00.0 (there is still resistance in the wires)
Here is the meter testing a good cartridge that is in-use
Here is the meter testing a good cartridge that is un-used
Here is the meter testing a bad cartridge (THCScientific says the resistance reading should be 5.4)
I'm sure a cheap tester could be made with an led, resistor and battery. A plug-in or screw-in socket would be easier than touching probes/wires to the cartridge.