Printers and encoders

1 . A printer for printing onto a substrate, the printer comprising:

a roller having a respective radius, the roller comprising a substrate engagement surface to rotate the roller in response to frictional coupling with a substrate;

a roller encoder to generate a roller encoder signal associated with rotation of the roller;

a mount to receive a carrier bearing the substrate;

a drive arranged to rotate the carrier;

a drive encoder to generate a drive encoder signal associated with rotation of the drive; and

a processor, responsive to the roller encoder signal and the drive encoder signal:

to determine a characteristic associated with the substrate;

wherein the processor to determine the characteristic associated with the substrate comprises logic or circuitry to:

determine a metric associated with the amount of substrate on the carrier, and

determine the radius of the substrate on the carrier using a measure of rotation of the drive, a measure of rotation of the roller and the respective radius.

2 . The printer of claim 1 , in which logic or circuitry to determine the radius of the substrate on the carrier using a measure of rotation of the drive, a measure of rotation of the roller and the respective radius comprises logic or circuitry to calculate the radius from R 1 =(ω_ 2 R 2 )/ω_ 1 , where R 1 is the radius of the substrate on the carrier, w_ 1 is a measure of rotation of the drive, R 2 is a respective radius of the roller, and w_ 2 is a measure of rotation of the roller and the respective radius R 2 .

3 . The printer of claim 1 , in which the processor, responsive to the roller encoder signal and the drive encoder signal, to determine a characteristic associated with the substrate comprises logic or circuitry to determine a state or movement status associated with the substrate.

4 . The printer of claim 3 , in which the logic or circuitry to determine a state or movement status associated with the substrate comprises logic or circuitry to determine a substrate movement error/jam of the substrate along a substrate path of the substrate through the printer.

5 . The printer of claim 4 , in which the logic or circuitry to determine the substrate movement error/jam of the substrate along the substrate path of the substrate through the printer comprises logic or circuitry to generate a signal indicating the substrate movement error/jam of the substrate in response to the drive encoder signal being indicative of movement of the drive in conjunction with the roller encoder signal being indicative of no movement of the roller.

6 . The printer of claim 5 , in which the logic or circuitry to generate a signal indicating the substrate movement error/jam of the substrate in response to the drive encoder signal being indicative of movement of the drive in conjunction with the roller encoder signal being indicative of no movement of the roller comprises logic or circuitry to generate the signal indicating the substrate movement error/jam of the substrate in response to the drive encoder signal being indicative of a forward or unspooling movement of the drive in conjunction with the roller encoder signal being indicative of no movement of the roller.

7 . The printer of claim 1 , in which the processor, responsive to the roller encoder signal and the drive encoder signal, to determine a characteristic associated with the substrate comprises logic or circuitry to generate a carrier present, or absent, signal indicating whether or not the carrier has been detected.

8 . The printer of claim 7 , in which the logic or circuitry to determine the carrier present, or absent, signal indicating whether or not the carrier has been detected comprises logic or circuitry to generate the carrier present, or absent, signal in response to the drive encoder signal being indicative of movement of the drive in conjunction with the roller encoder signal being indicative of no movement of the roller.

9 . The printer of claim 8 , in which the logic or circuitry to generate the carrier present in response to the drive encoder signal being indicative of movement of the drive in conjunction with the roller encoder signal being indicative of no movement of the roller comprises logic or circuitry to generate the carrier present signal indicating whether or not the carrier has been detected in response to the drive encoder signal being indicative of a backward movement of the drive in conjunction with the roller encoder signal being indicative of no movement of the roller.

10 . A non-transitory readable storage storing machine readable instructions, arranged when implemented in a processor, to process a roller encoder signal, associated with rotation of a substrate engaging roller, and a drive encoder signal, associated with a drive for rotating a carrier bearing the substrate, to determine a characteristic associated with the substrate,

wherein the instructions to determine the characteristic associated with the substrate comprise further instructions to determine at least one of:

a measure associated with a volume of substrate on the carrier,

an error condition associated with the substrate,

absence of the substrate, or

presence of the substrate, and

wherein the instructions further comprise at least one of instructions:

to generate the signal indicating the substrate movement error of the substrate in response to the drive encoder signal being indicative of a forward or unspooling movement of the drive in conjunction with the roller encoder signal being indicative of no movement of the roller, or

to generate the carrier present signal indicating whether or not the carrier has been detected in response to the drive encoder signal being indicative of a backward movement of the drive in conjunction with the roller encoder signal being indicative of no movement of the roller.