Examples of a print liquid supply unit are described herein. In some examples, the print liquid supply unit includes a first housing component that is welded to a second housing component along a supply joint. In some examples, the print liquid supply unit also includes a conductor situated through the supply joint from an outside of the supply unit to an inside of the supply unit. In some examples, the conductor is sealed in the supply joint with a sealing material.

A print head includes a nozzle array comprising a plurality of nozzles, and a negative pressure generating portion configured to apply a negative pressure to the nozzle array. A tank includes a storage portion and an air communication port. A tube connects the print head and the tank and supply the liquid from the tank to the print head. A highest position of a liquid level in the tank in the vertical direction is higher than a position of the nozzle array, and an absolute value of a water head difference caused by a difference between the highest position of the liquid level in the tank and the position of the nozzle array is not larger than an absolute value of a negative pressure generated by the negative pressure generating portion.

Operating a fluid delivering system in a printer, wherein the fluid delivering system comprises a fluid supply including a fluid bag which contains a fluid to be delivered to a fluid delivering tube connected to a printhead, and a closed pressurizing volume which surrounds the fluid bag to expel fluid from the fluid bag to the fluid delivering tube when applying pressure from a pressurizing system to the pressurizing volume, wherein pressure in the pressurizing system relative to atmosphere is measured by a first sensor, and wherein a second sensor provides an output signal which indicates a pressure difference between the pressurizing system and the fluid delivering tube, comprising disconnecting the pressurizing volume of the fluid supply from the pressurizing system, providing a connection of the pressurizing volume to atmosphere to transmit atmospheric pressure to the fluid, generating pressure in the pressurizing system, performing measurements of the pressure in the pressurizing system relative to atmosphere by the first sensor, and calibrating the second sensor by the measurements of the first sensor.

A printable liquid supply cartridge comprises a housing enclosing an internal volume. The housing has a front end to connect to a printer and first and second sides extending from the front end to a rear end. The front end has a printable liquid outlet closer to the bottom than to the top and has a gas inlet above the printable liquid outlet, each of the printable liquid outlet and the gas inlet to facilitate insertion of a respective fluid pen therein. There is a recess in the front end above the gas inlet, the recess being delimited by a first wall having an internal side and an external side that is part of the first side. An I2C data interface comprising at least three electrical connection pads are exposed on the internal side of the first wall facing towards the recess, the connection pads arranged in a top to bottom direction.

A logic circuitry package for a replaceable print apparatus component includes an interface to communicate with a print apparatus logic circuit and at least one logic circuit. The at least one logic circuit is configured to receive, via the interface, a request to replace an internal clock signal from an internal clock generator of the logic circuitry package with an external test clock signal. The at least one logic circuit is configured to receive, via the interface, the external test clock signal. The at least one logic circuit is configured to replace the internal clock signal with the external test clock signal in the logic circuitry package.

Examples of a print liquid supply unit are described herein. In some examples, the print liquid supply unit includes a first housing component that is welded to a second housing component along a supply joint. In some examples, the print liquid supply unit also includes a conductor situated through the supply joint from an outside of the supply unit to an inside of the supply unit. In some examples, the conductor is sealed in the supply joint with a sealing material.

A logic circuitry package for a replaceable print apparatus component comprises at least one logic circuit and an interface to communicate with a print apparatus logic circuit. The at least one logic circuit is configured to receive, via the interface, calibration parameters including an offset parameter and a sensor ID. The at least one logic circuit is configured to output, via the interface, a digital value corresponding to the sensor ID and offset based on the offset parameter.

A logic circuitry package for a replaceable print apparatus component includes an interface to communicate with a print apparatus logic circuit and at least one logic circuit. The at least one logic circuit is configured to receive, via the interface, a request and a reference clock signal. The at least one logic circuit is configured to transmit, via the interface, a digital value indicating a count in response to the request and the reference clock signal. The digital value varies based on the reference clock signal.

A logic circuitry package includes an interface to communicate with a print apparatus logic circuit and at least one logic circuit. The logic circuit is configured to receive, via the interface, a plurality of first requests in a heater disabled mode, each first request corresponding to a different sensor ID of a plurality of sensor IDs; transmit, via the interface, a first digital value in response to each first request; receive, via the interface, a plurality of second requests in a heater enabled mode, each second request corresponding to a different sensor ID of the plurality of sensor IDs; and transmit, via the interface, a second digital value in response to each second request. Delta values corresponding to a difference between the first digital value and the second digital value for each different sensor ID of the plurality of sensor IDs are indicative of a print material level.

A replaceable print apparatus component includes a print material reservoir, a print material within the reservoir and a sensing system including an integrated circuit configured to connect to and communicate over a digital bus. The sensing system includes at least one sensor, a digital controller, an analog to digital converter electrically coupled to the digital controller, and a memory array electrically coupled to the digital controller. The digital controller is configured to generate a clock signal for timing operations of the integrated circuit. The operations include initiating the at least one sensor based on values stored in the memory array and generating outputs of the at least one sensor via the analog to digital converter.