Testing for correct operation of micro electromechanical device
View Patent ↗A method of testing a micro electro-mechanical device in the form of an ink ejection nozzle having an actuating arm that moves an ink displacing paddle when heat inducing electric current is passed through the actuating arm and having a movement sensor associated with the actuating arm. The method comprises the steps of passing a series of current pulses having varying durations through the actuating arm and detecting for a predetermined level of movement of the actuating arm, obtaining a movement versus pulse duration characteristic and comparing the detected characteristic with a desired characteristic.
1. A method of testing a micro electro-mechanical device of a type having a support structure, an actuating arm that is movable relative to the support structure between a rest position and an operating position under the influence of heat inducing current flow through the actuating arm and a movement sensor associated with the actuating arm, said movement sensor being activated by movement of the actuating arm to a predetermined position beyond said operating position; the method comprising the steps of:
(a) passing a series of current pulses of varying duration through the actuating arm, and
(b) for each current pulse, detecting for movement of the actuating arm to said predetermined position,
(c) obtaining a movement versus pulse duration characteristic for the device, and
(d) comparing said movement versus pulse duration characteristic with a desired movement versus pulse duration characteristic.
2. The method as claimed in claim 1 when employed in relation to a liquid ejection nozzle having a liquid receiving chamber from which the liquid is ejected with movement of the actuating arm to said operating position.
3. The method as claimed in claim 1 when employed in relation to an ink ejection nozzle having an ink receiving chamber from which the ink is ejected with movement of the actuating arm to said operating position.
4. The method as claimed in claim 3 wherein the movement sensor comprises a moving contact element formed integrally with the actuating arm, a fixed contact element formed integrally with the support structure and electric circuit elements formed within the support structure, and wherein contact is made between the fixed and moving contact elements at said predetermined position of the operating arm.
5. The method as claimed in claim 3 wherein a series of current pulses of successively increasing duration t p are induced to pass through the actuating arm over a time period t and detection is made for movement of the actuating arm to said predetermined position within a predetermined time window t w where t>t w >t p .
6. A method of detecting and remedying a fault within a micro electro-mechanical device of a type having a support structure, an actuating arm that is movable relative to the support structure between a rest position and an operating position under the influence of heat inducing current flow through the actuating arm and a movement sensor associated with the actuating arm, said movement sensor being activated by movement of the actuating arm to a predetermined position beyond said operating position; the method comprising the steps of:
(a) detecting a fault in the manner as claimed in claim 1 , and
(b) remedying the fault by passing at least one further current pulse through the actuating arm at an energy level greater than that of the fault detecting current pulse.