Calibration of a sensor

A system for calibrating an uncalibrated sensor, the system comprising:

• an uncalibrated sensor;
• a source of ink solution of a first colour, the ink solution of the first colour comprising concentrated ink of the first colour dissolved in a solvent;
• and processing apparatus to:
• receive calibrated sensor data indicative of light transmission through an ink solution of a first colour as a function of ink concentration;
• measure, using the uncalibrated sensor, at a plurality of ink concentrations, light transmission through an ink solution of the first colour;
• and
• determine, based on the received data and the measurements, a calibration factor relating the light transmission of the calibrated sensor for the first colour and the light transmission of the uncalibrated sensor for the first colour.

A machine-readable medium comprising instructions which, when executed by a processor, cause the processor to:

• obtain data indicative of light transmission through an print agent solution of a first colour as a function of print agent concentration, the data relating to a calibrated sensor;
• measure, using an uncalibrated sensor, at a plurality of print agent concentrations, light transmission through a print agent solution of the first colour;
• and
• establish, using processing apparatus, based on the obtained data and the measurements, a calibration factor between the obtained light transmission data of the calibrated sensor for the first colour and measured light transmission data of the uncalibrated sensor for the first colour.