An example printing cartridge includes a fluid container, a plurality of sensing locations in thermal contact with the fluid container, a voltage comparator to output time-based information based on a comparison of a sensed voltage generated at a selected sensing location of the plurality of sensing locations to a threshold voltage, the time-based information representative of whether a fluid is present at a fluid level associated with the selected sensing location, and a counter to convert the time-based information to a digital code based on a number of clock cycles.