Fluid level sensor

A fluid reservoir comprising:

• a number of metal traces along a wall of the fluid reservoir;
• a number of fuse circuits along a length of the metal traces, wherein each of the fuse circuits comprises:
• a fuse along a length of a respective metal trace;
• and
• a number of parasitic resistive elements in parallel to the fuse, the parasitic resistive elements reducing current flow through the fuse in the presence of a fluid contained within the fluid reservoir.

A fluid cartridge comprising:

• a fluid reservoir comprising walls defining an interior chamber, the fluid reservoir to store fluid in the interior chamber;
• a number of fuse circuits formed along a length of at least one wall of the fluid reservoir such that a respective position of each respective fuse circuit of the number of fuse circuits corresponds to a fluid level of the fluid reservoir, each respective fuse circuit to change state when the fluid level of the fluid reservoir crosses the respective position of the respective fuse circuit;
• and
• a fluid ejection die fluidly coupled to the fluid reservoir, the fluid ejection die comprising nozzles to eject fluid conveyed from the fluid reservoir, the fluid ejection die further comprising a programmable memory device electrically coupled to the number of fuse circuits, the programmable memory device to permanently change data stored thereon responsive to a change in state of each respective fuse circuit.