Self diagnostic measurement method to detect microbridge null drift and performance
First Claim
1. A method to detect microbridge null performance in a microbridge sensor, the microbridge sensor including a heater element and a microbridge including a plurality of temperature sensitive resistors, the method comprising:
- not applying power to the heater element and the microbridge;
waiting a time period without applying power to the heater element and the microbridge;
applying diagnostic power to the microbridge after the waiting step at a diagnostic power level that is reduced relative to an operational power level, resulting in a reduced bias current in the plurality of temperature sensitive resistors relative to when the operational power level is applied;
measuring a microbridge null offset voltage while the reduced bias current is being applied to the plurality of temperature sensitive resistors of the microbridge; and
applying operational power to the microbridge at the operational power level, resulting in an increased bias current in the plurality of temperature sensitive resistors relative to when the diagnostic power level was applied.
1 Assignment
0 Petitions
Accused Products
Abstract
A self-diagnostic measurement method to detect microbridge null drift and performance. An ASIC can be designed to include a self-diagnostic feature that automatically occurs at start up or upon command in Normal Operation whereby the temperature compensated microbridge null can be measured in a state of very low thermal energy and allows for the tracking of microbridge null stability versus time. An Airflow Combi-Sensor ASIC (Heimdal) with its strategic partner ZMD can be developed and can be implemented in the form of a self-diagnostic feature that occurs when power is first applied to the ASIC or upon command. When the self-diagnostic is initiated, power is removed and after the electronics have settled, a small power can be applied to the microbridge to measure the bridge null with reduced sensitivity to flow due to self-heating.
-
Citations
18 Claims
-
1. A method to detect microbridge null performance in a microbridge sensor, the microbridge sensor including a heater element and a microbridge including a plurality of temperature sensitive resistors, the method comprising:
-
not applying power to the heater element and the microbridge; waiting a time period without applying power to the heater element and the microbridge; applying diagnostic power to the microbridge after the waiting step at a diagnostic power level that is reduced relative to an operational power level, resulting in a reduced bias current in the plurality of temperature sensitive resistors relative to when the operational power level is applied; measuring a microbridge null offset voltage while the reduced bias current is being applied to the plurality of temperature sensitive resistors of the microbridge; and applying operational power to the microbridge at the operational power level, resulting in an increased bias current in the plurality of temperature sensitive resistors relative to when the diagnostic power level was applied. - View Dependent Claims (2, 3, 4, 5, 7, 16, 17, 18)
-
-
6. A method to detect microbridge null offset in an ASIC, the ASIC including a heater element, a microbridge including a plurality of temperature sensitive resistors, and a controller configured to execute the self diagnostic measurement method, the method comprising:
-
removing power from the heater element and the microbridge; waiting a time period without applying power to help dissipate thermal energy that was generated by power previously applied to the heater element and the microbridge; applying diagnostic power to the microbridge after the waiting step at a diagnostic power level that is reduced relative to an operational power level, resulting in a reduced bias current in the plurality of temperature sensitive resistors relative to when the operation power level is applied; measuring a microbridge null offset voltage while the reduced bias current is being applied to the plurality of temperature sensitive resistors of the microbridge; and applying operational power to the microbridge at the operational power level, resulting in an increased bias current in the plurality of temperature sensitive resistors relative to when the diagnostic power level was applied. - View Dependent Claims (8, 9, 10)
-
-
11. A mass airflow sensor ASIC, the ASIC comprising:
-
a heater element; a microbridge including a plurality of temperature sensitive resistors; and a controller programmed to; withhold power from the heating element and microbridge; wait a time period while withholding power from the heating element and microbridge; apply diagnostic power to the microbridge at a diagnostic power level that is reduced relative to an operational power level, resulting in a reduced bias current in the plurality of temperature sensitive resistors relative to when the operation power level is applied; measure a microbridge null offset voltage while the reduced bias currents propagate through the plurality of temperature sensitive resistors of the microbridge; and apply operational power to the microbridge at the operational power level, resulting in an increased bias current in the plurality of temperature sensitive resistors relative to when the diagnostic power level was applied. - View Dependent Claims (12, 13, 14, 15)
-
Specification