System and method for monitoring performance of air filter

Abstract

A system includes a device including a substrate, a resistor disposed on the substrate, and a thermistor disposed on the substrate and thermally coupled to the resistor. The system further includes a control unit including a power source and a controller. The controller is communicably coupled to the resistor and the power source. The controller is configured to: supply, via the power source, electrical power to the resistor for a time period extending from a first time instance to a second time instance; determine, via the thermistor, a variation of the temperature of the resistor during the time period; and determine an airflow speed based on the variation of the temperature of the resistor in the time period. The system may further include an air filter proximal to which the device may be disposed. The controller may be further configured to determine a filter parameter based on the airflow speed.

What is claimed is: 
     
         1 . A system for monitoring a performance of an air filter, the system comprising:
 a device comprising:
 a substrate; 
 at least one resistor disposed on the substrate; and 
 at least one thermistor disposed on the substrate and thermally coupled to the at least one resistor; and 
   a control unit comprising:
 a power source electrically connected to the at least one resistor and configured to supply electrical power to the at least one resistor; and 
 a controller communicably coupled to the at least one thermistor and the power source, wherein the controller is configured to:
 supply, via the power source, the electrical power to the at least one resistor for a time period extending from a first time instance to a second time instance, such that a temperature of the at least one resistor at the second time instance is greater than the temperature of the at least one resistor at the first time instance; 
 determine, via the at least one thermistor, a variation of the temperature of the at least one resistor during the time period; and 
 determine an airflow speed based on the variation of the temperature of the at least one resistor in the time period. 
 
   
     
     
         2 . The system of  claim 1 , wherein the substrate comprises polyimide. 
     
     
         3 . The system of  claim 1 , wherein supplying the electrical power to the at least one resistor via the power source comprises applying a constant voltage across the at least one resistor. 
     
     
         4 . The system of  claim 1 , wherein:
 determining the variation of the temperature of the at least one resistor during the time period via the at least one thermistor comprises determining, via the at least one thermistor, a temperature curve representing the variation of the temperature of the at least one resistor during the time period; and   determining the airflow speed based on the variation of the temperature of the at least one resistor in the time period comprises determining the airflow speed based on the temperature curve.   
     
     
         5 . The system of  claim 1 , wherein:
 determining the variation of the temperature of the at least one resistor during the time period via the at least one thermistor comprises:
 determining, via the at least one thermistor, a first temperature of the at least one resistor at the first time instance; 
 determining, via the at least one thermistor, a second temperature of the at least one resistor at the second time instance; and 
 determining a temperature differential between the first temperature and the second temperature; and 
   determining the airflow speed based on the variation of the temperature of the at least one resistor in the time period comprises determining the airflow speed based on the temperature differential.   
     
     
         6 . The system of  claim 1 , wherein the at least one thermistor is a negative temperature coefficient thermistor. 
     
     
         7 . The system of  claim 1 , further comprising a fixture configured to support the device, wherein the fixture comprises a through aperture, and wherein the at least one resistor is positioned at the through aperture. 
     
     
         8 . The system of  claim 1 , wherein the device further comprises:
 a plurality of resistor electrical traces disposed on the substrate and electrically connected to the at least one resistor; and   a plurality of thermistor electrical traces disposed on the substrate and electrically connected to the at least one thermistor.   
     
     
         9 . The system of  claim 1 , wherein the controller comprises:
 a first input port configured to receive a first signal;   a second input port configured to receive a second signal, wherein the controller is configured to measure a voltage difference between the first signal and the second signal; and   an output port configured to be connected to the at least one resistor, wherein the controller is configured to apply a voltage across the at least one resistor through the output port.   
     
     
         10 . The system of  claim 9 , further comprising an electrical circuit, the electrical circuit comprising:
 the at least one resistor;   the at least one thermistor connected in parallel with the at least one resistor;   at least one first circuit resistor connected in series with the at least one thermistor;   a first circuit node disposed between the at least one thermistor and the at least one first circuit resistor, wherein the first circuit node is configured to be connected to the first input port of the controller;   at least one second circuit resistor connected in parallel with the at least one thermistor and the at least one first circuit resistor;   at least one third circuit resistor connected in series with the at least one second circuit resistor; and   a second circuit node disposed between the at least one second circuit resistor and the at least one third circuit resistor, wherein the second circuit node is configured to be connected to the second input port of the controller.   
     
     
         11 . The system of  claim 10 , wherein:
 the electrical circuit further comprises:
 a first connection node, wherein the at least one second circuit resistor is disposed between the second circuit node and the first connection node; and 
 a second connection node, wherein the at least one third circuit resistor is disposed between the second circuit node and the second connection node; 
   the controller further comprises:
 at least one first controller resistor; 
 at least one second controller resistor connected in series with the at least one first controller resistor; 
 a controller node disposed between the at least one first controller resistor and the at least one second controller resistor, wherein the controller node is configured to be connected to the second circuit node; 
 a first switch connected in series with the at least one first controller resistor, wherein the first switch is configured to be connected between the controller node and the first connection node; and 
 a second switch connected in series with the at least one second controller resistor, wherein the second switch is configured to be connected between the controller node and the second connection node; and 
   the controller is further configured to selectively operate each of the first switch and the second switch.   
     
     
         12 . The system of  claim 1 , further comprising an air filter, wherein the device is disposed proximal to the air filter, and wherein the controller is further configured to determine a filter parameter associated with the air filter based at least on the airflow speed. 
     
     
         13 . The system of  claim 12 , wherein the filter parameter comprises a clogging level of the air filter. 
     
     
         14 . The system of  claim 12 , further comprising a pressure sensor disposed proximal to the air filter and communicably coupled to the controller, wherein the controller is further configured to determine, via the pressure sensor, a pressure, and wherein the filter parameter is determined further based on the pressure. 
     
     
         15 . The system of  claim 14 , further comprising a temperature sensor disposed proximal to the air filter and communicably coupled to the controller, wherein the controller is further configured to determine, via the temperature sensor, a temperature, and wherein the filter parameter is determined further based on the temperature. 
     
     
         16 . The system of  claim 12 , wherein the controller is configured to be communicably coupled to a terminal device, and wherein the controller is further configured to communicate the filter parameter to the terminal device. 
     
     
         17 . A method for monitoring a performance of an air filter, the method comprising:
 providing a device comprising:
 a substrate; 
 at least one resistor disposed on the substrate; and 
 at least one thermistor disposed on the substrate and thermally coupled to the at least one resistor; 
   supplying, via a power source, electrical power to the at least one resistor for a time period extending from a first time instance to a second time instance, such that a temperature of the at least one resistor at the second time instance is greater than the temperature of the at least one resistor at the first time instance;   determining, via the at least one thermistor, a variation of the temperature of the at least one resistor during the time period; and   determining an airflow speed based on the variation of the temperature of the at least one resistor in the time period.   
     
     
         18 . The method of  claim 17 , wherein:
 determining the variation of the temperature of the at least one resistor during the time period via the at least one thermistor comprises determining, via the at least one thermistor, a temperature curve representing the variation of the temperature of the at least one resistor during the time period; and   determining the airflow speed based on the variation of the temperature of the at least one resistor in the time period comprises determining the airflow speed based on the temperature curve.   
     
     
         19 . The method of  claim 17 , wherein:
 determining the variation of the temperature of the at least one resistor during the time period via the at least one thermistor comprises:
 determining, via the at least one thermistor, a first temperature of the at least one resistor at the first time instance; 
 determining, via the at least one thermistor, a second temperature of the at least one resistor at the second time instance; and 
 determining a temperature differential between the first temperature and the second temperature; and 
   determining the airflow speed based on the variation of the temperature of the at least one resistor in the time period comprises determining the airflow speed based on the temperature differential.   
     
     
         20 . The method of  claim 17 , further comprising:
 disposing the device proximal to an air filter; and   determining a filter parameter associated with the air filter based at least on the airflow speed.