Thermal printer
AssigneeVideojet Technologies Inc.
InventorsKeith Buxton, Philip Hart, Jeremy Ellis
Life of this patent
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Abstract
An apparatus for determining the resistance of a printing element of a print head, the apparatus comprising: a print head comprising a plurality of individually controllable printing elements connected in parallel, and a capacitor connected in parallel with the printing elements; a test voltage supply arranged to supply a test voltage to the print head; a current monitor arranged to measure the current supplied to one of the printing elements when the said one of the printing elements is connected to the test voltage supply; and a controller arranged to determine the resistance of the said one of the printing elements based upon the measured current.
Claims20
An apparatus for determining the resistance of a printing element of a print head, the apparatus comprising:
- a print head comprising a plurality of individually controllable printing elements connected in parallel, and a capacitor connected in parallel with the printing elements;
- a test voltage supply arranged to supply a test voltage to the print head;
- a current monitor arranged to measure a current supplied to one of the printing elements when the said one of the printing elements is connected to the test voltage supply, wherein the current monitor has a lower resistance than a nominal resistance of a printing element;
- and
- a controller arranged to determine a resistance of the said one of the printing elements based upon the measured current.
A method of determining the resistance of at least two printing elements of a print head, the print head comprising a plurality of individually controllable printing elements connected in parallel, and a capacitor connected in parallel with the printing elements, the method comprising:
- connecting a first one of the printing elements to a test voltage;
- waiting for a predetermined time period;
- measuring a current drawn by the first one of the printing elements from the test voltage;
- and
- determining a resistance of the first one of the printing elements based upon the measured current;
- the method further comprising:
- disconnecting the first one of the printing elements from the test voltage;
- connecting a second one of the printing elements to the test voltage;
- waiting for a time period less than the predetermined time period;
- measuring a second current drawn by the second one of the printing elements from the test voltage;
- and
- determining a resistance of the second one of the printing elements based upon the measured second current.
Dependencies are inferred from the claim text.