Measuring magnetic debris buildup in a magnetic filter

Abstract

A magnetic debris level measuring device for a magnetic filter is disclosed. The magnetic debris level measuring device includes a magnetometer and a temperature sensor. The temperature measured by the temperature sensor is used to calculate a corrected magnetometer reading, which in turn can be used to determine the amount of captured magnetic debris held within the filter. The device has a stored threshold for the corrected magnetometer reading, and when the corrected magnetometer reading crosses the stored threshold a notification is issued that the filter is full. If it is detected that debris continues to be captured after the ‘full’ notification has been issued, the stored threshold will be updated accordingly.

What is claimed is: 
     
         1 . A captured debris level measuring device for a magnetic filter in a central heating system, the magnetic filter including a separation chamber, an inlet to the chamber and an outlet from the chamber, and a magnetic element disposed within the chamber for attracting magnetic debris and removing the magnetic debris from the system water as it flows through the chamber, and the captured debris measuring device comprising:
 a magnetometer for mounting to the magnetic filter to measure magnetic field strength due to the magnet and any captured magnetic debris; and   a control unit, the magnetometer being connected to an input of the control unit, and the control unit being adapted to issue a notification on output means when the magnetic field strength measured by the magnetometer exceeds or drops below a stored threshold,   the control unit further being adapted to monitor the magnetic field strength measured by the magnetometer after the notification is issued, and in the case that the measured magnetic field strength rises further above the threshold or drops further below the threshold, to update the stored threshold according to the measured reading.   
     
     
         2 . The captured debris level measuring device of  claim 1 , wherein the measured magnetic field strength is a raw measurement from the magnetometer. 
     
     
         3 . The captured debris level measuring device of  claim 1 , wherein the measured magnetic field strength is a corrected magnetic field strength. 
     
     
         4 . The captured debris level measuring device of  claim 3 , wherein the corrected magnetic field strength is calculated to compensate from temperature, based on a temperature reading taken from a temperature sensor. 
     
     
         5 . The captured debris level measuring device of  claim 3 , wherein the corrected magnetic field strength is an average or other amalgamation of several readings to compensate for noise. 
     
     
         6 . A magnetic filter for a central heating system, fitted with the captured debris level measuring device of  claim 1 . 
     
     
         7 . The captured debris level measuring device of  claim 1 , wherein the control unit includes data transmission means and is adapted to transmit magnetic field strength data to a central server. 
     
     
         8 . A method of measuring the amount of magnetic debris captured within a magnetic filter in a central heating system, the magnetic filter having a chamber with an inlet and outlet connected to the central heating system circuit, and a magnet provided within the chamber, the method comprising:
 providing a magnetometer mounted to the magnetic filter;   providing a temperature sensor mounted to the magnetic filter;   calculating a corrected magnetometer reading from the magnetometer reading and the temperature sensor reading, and using the corrected magnetometer reading to determine when the amount of debris captured within the filter exceeds a threshold level.   
     
     
         9 . The method of  claim 8 , wherein the corrected magnetometer reading y c  is calculated as:
     y   c =( y   0   −t   x )+ C      where y 0  is the raw magnetometer reading taken from the magnetometer, t is the temperature measured by the temperature sensor, x is a correction exponent and C is a constant.   
     
     
         10 . The method of  claim 9 , wherein the correction exponent x is determined according to: 
       
         
           
             
               x 
               = 
               
                 
                   log 
                   ⁡ 
                   ( 
                   
                     
                       t 
                       1 
                     
                     - 
                     
                       t 
                       2 
                     
                   
                   ) 
                 
                 
                   log 
                   ⁡ 
                   ( 
                   
                     
                       y 
                       1 
                     
                     - 
                     
                       y 
                       2 
                     
                   
                   ) 
                 
               
             
           
         
         where y 1  is the magnetometer reading at temperature t 1  and y 2  is the magnetometer reading at temperature t 2 , where y 1 , t 1 , y 2 , t 2  are obtained experimentally for a constant amount of magnetic debris within the filter. 
       
     
     
         11 . The method of  claim 8 , wherein the corrected magnetometer reading is compared to a stored threshold level, the notification being issued when the corrected magnetometer reading exceeds or drops below the stored threshold level. 
     
     
         12 . The method of  claim 8 , wherein the corrected magnetometer readings continue to be calculated after the amount of debris has been detected to exceed a threshold level, and where the detected amount of debris continues to increase, the threshold level is increased. 
     
     
         13 . The method of  claim 8 , wherein a corrected magnetometer reading is calculated only using a temperature reading taken when the temperature detected by the temperature sensor has not changed more than a predetermined temperature difference for a predetermined period of time. 
     
     
         14 . The method of  claim 13 , in which the predetermined temperature difference is 1° C. 
     
     
         15 . The method of  claim 13 , in which the predetermined time is at least one minute. 
     
     
         16 . The method of  claim 8 , wherein the method further includes outputting an indication of the amount of magnetic debris currently retained within the filter. 
     
     
         17 . The method of  claim 8 , wherein the temperature sensor is provided in contact with an outside wall of the chamber of the magnetic filter.