Element substrate, printhead and printing apparatus

1. An element substrate comprising:

a first driving element and a second driving element for generating energy;

a first resistance element corresponding to said first driving element and a second resistance element corresponding to said second driving element, each of the first and second resistance elements including a first terminal and a second terminal, wherein the first terminals of said first resistance element and said second resistance element are connectable through switches to a first line for supplying a first current, and the second terminals of said first resistance element and second resistance element are commonly connected to a second line for supplying a second current;

a selection unit connected to the switches and configured to selectively supply power to the first and second resistance elements; and

a detection unit configured to detect a voltage of the first terminal of said first resistance element and a voltage of the first terminal of said second resistance element while the power is supplied to said first resistance element and is not supplied to said second resistance element,

wherein said first driving element, said first resistance element, said second driving element and said second resistance element are arranged in one line.

2. The substrate according to claim 1 , wherein a current path length for supplying the first or second current to said second resistance element is longer than a current path length for supplying the first or second current to said first resistance element.

3. The substrate according to claim 1 , wherein the sum of the length of the first line and the length of the second line for supplying the first and second currents to said second resistance element is longer than the sum of the length of the first line and the length of the second line for supplying the first and second currents to said first resistance element.

4. The substrate according to claim 1 , wherein when the selection unit effects supplying of the power to said first resistance element and said second resistance element, a constant current as the first current is supplied to said first resistance element and said second resistance element.

5. The substrate according to claim 1 , wherein the selection unit is configured to select one of said first resistance element and said second resistance element as a resistance element which supplies a constant current as the first current.

6. The substrate according to claim 1 , wherein the switches are arranged in correspondence with said first resistance element and said second resistance element, for switching between a state in which the power is supplied and a state in which no power is supplied.

7. The substrate according to claim 1 , wherein said detection unit includes an input unit configured to input a voltage, and said input unit has a high input resistance to prevent one of the first and second currents from flowing into said input unit.

8. A printhead comprising:

a nozzle plate having nozzles through which ink is discharged; and

the element substrate according to claim 1 connected to the nozzle plate and generating the energy to discharge the ink.

9. A printing apparatus comprising:

a current generation unit configured to generate the first or second current; and

a printhead control unit configured to control an operation of the element substrate according to claim 1 .