Method and apparatus for testing microwave ovens

• US 4,565,967 A
• Filed: 06/21/1982
• Issued: 01/21/1986
• Est. Priority Date: 06/21/1982
• Status: Expired due to Fees

• Current Assignee: Whirlpool Corporation
• Original Assignee: Whirlpool Corporation
• Inventors: Eisenbrandt, Gerald A., Marks, James R.
• Primary Examiner(s): Karlsen, Ernest F.
• Application Number:
  US06/390,788
• Time in Patent Office: 1,310 Days
• Field of Search: 324/95, 324/106, 219/10.55 D
• US Class Current: 324/95
• CPC Class Codes: G01R 21/04 in circuits having distributed constants
• CPC Class Codes: G01R 29/0814 Field measurements related to measuring influence on or from apparatus, components or humans EMC, EMI and similar testing in general G01R31/001, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning

Abstract

A method and apparatus for testing microwave ovens to determine if exterior radiation levels exceed permissible maxima. The leakage levels are sensed by a sensor moved along a preselected path accurately spaced from the oven cabinet. The probe is moved automatically at high speed along the path until a leakage level above a preselected value is sensed. A control associated with the apparatus automatically causes the sensor to move subsequently at a reduced speed to determine the maximum leakage at that position. The control causes a repeated traverse of the questioned position at the slow speed to provide an accurate maximum leakage determination. The control includes reference information indicating acceptable levels of leakage along the path of movement of the sensor which are continuously compared with actual sensed values. Different factors are applied to the reference values correlated with the speed of movement of the sensor and the desired coarse or fine scanning accuracy to permit the selective, high speed movement of the sensor between all high leakage positions. Information concerning the location of the high leakage positions is provided at the end of the test to permit facilitated correction of any leakage problems found. The control may further include structure for tagging the device being tested and for other suitable disposition thereof, as desired. The apparatus in the illustrated embodiment includes a robot for automatically moving the sensor along the desired path and an associated control for effecting the desired high speed-low speed movement in providing the rapid determination of high leakage positions.

Claims

1. Apparatus for determining microwave leakage characteristics of a microwave oven for use in quality control of the manufacture of such ovens, comprising:

a microwave energy sensor;

means for moving the sensor at high speed adjacent the oven to sense microwave leakage therefrom;

first control means for causing the moving means to move the sensor at slower speeds whenever an elevated level of leakage is sensed; and

second control means for identifying the location of the sensed levels having a maximum leakage above a preselected amount, said second control means including reference means for comparing the sensed leakage with preselected values for acceptable leakage for said identified location, said reference values being adjusted by a factor correlated with the speed of the sensor.

2. The apparatus of claim 1 wherein said sensor comprises a plurality of probes.

3. The apparatus of claim 1 wherein said sensor comprises a plurality of spaced probes for simultaneously sensing leakage at different spaced points on said path.

4. The apparatus of claim 1 wherein said means for moving the sensor at high speed comprises means for moving the sensor along a preselected path at a speed of at least approximately 4" per second therealong.

5. The apparatus of claim 1 wherein said means for moving the sensor at high speed comprises means for moving the sensor along a preselected path at a speed of 4" per second therealong.

6. The apparatus of claim 1 wherein said means for moving the sensor at high speed includes means for moving the sensor along a preselected path including a plurality of segment scans adjacent the oven to be inspected, means for providing a signal corresponding to the microwave energy levels scanned by the sensor as it is moved at high speed along said path, and means for providing an indication whenever the level of microwave energy leakage sensed by the rapidly moving sensor at a position in said path exceeds the acceptable level thereat.

7. The apparatus of claim 1 wherein said means for moving the sensor at high speed includes means for moving the sensor along a preselected path including a plurality of segment scans adjacent the oven to be inspected, means for providing a signal corresponding to the microwave energy levels scanned by the sensor as it is moved at high speed along said path, and means for providing an indication whenever the level of microwave energy leakage sensed by the rapidly moving sensor at a position in said path exceeds the acceptable level thereat, and means for redetermining the microwave energy leakage at said position while moving the sensor at a speed lower than said high speed to provide an increased accuracy determination of the microwave leakage thereat.

8. The apparatus of claim 1 including means for causing redetermination of the sensed leakage at each such location while retraversing each such location at lower speed thereby to provide increased accuracy in the determination of leakage at each said location.

9. The apparatus of claim 1 wherein said means for moving the sensor at high speed comprises mechanism for moving the sensor rapidly along a preselected path including a plurality of segment scans at a speed of approximately 4" or more per second.

10. The apparatus of claim 9 wherein said mechanism comprises a robot and control means for automatically operating the robot to move said sensor along said path, said control means including means for changing the speed of the sensor movement by the robot in accordance with said signals produced by said sensor.

11. The apparatus of claim 1 wherein said means for moving the sensor at high speed comprises mechanism for moving the sensor rapidly along a preselected path including a plurality of segment scans at a speed of approximately 4" or more per second, means for providing a signal corresponding to the microwave energy levels scanned by the sensor as it is moved at said high speed along said path by said mechanism, means for providing a reference corresponding to acceptable levels of microwave energy leakage as sensed by the sensor as it is moved at said high speed along said path, and means for providing an indication whenever the level of microwave energy leakage sensed by the rapidly moving sensor at a position in said path exceeds the acceptable level thereat.

12. The apparatus of claim 11 wherein said mechanism comprises a robot and control means for automatically operating the robot to move said sensor along said path, said reference providing means including information storage means for storing information as to acceptable levels of leakage along said path for comparison with the actual levels sensed by said sensor to determine the operation of said control means, said control means being automatically actuated to modify said preselected path pattern and the movement speed of said sensor in response to sensing of an unacceptable high leakage level.

13. The apparatus of claim 1 wherein said means for moving the sensor at high speed comprises mechanism for moving the sensor rapidly along a preselected path including a plurality of segment scansat a speed of approximately 4" or more per second, means for providing a signal corresponding to the microwave energy levels scanned by the sensor as it is moved at said high speed along said path by said mechanism, means for providing a reference corresponding to acceptable levels of microwave energy leakage as sensed by the sensor as it is moved at said high speed along said path, means for providing an indication whenever the level of microwave energy leakage sensed by the rapidly moving sensor at a position in said path exceeds the acceptable level thereat, and means for redetermining the microwave energy leakage at said position while moving the sensor at a speed lower than said high speed to provide an increased accuracy determination of the microwave leakage thereat.

14. The apparatus of claim 13 wherein said control is arranged to cause a repeated traverse of the portion of the path at said position while causing the accuracy of the scan by the sensor to be increased during the repeated traverse by a low speed factor of approximately 0.95 where the factor is determined by the equation 1-maximum measurable error as resulting from the instrumentation time response or filtering per theoretical computation for fast or slow instrumentation field probe speed past the potential narrowest beam leakage radiation pattern generated by a given design microwave oven including variation such as that generated by a load stirrer, where the accuracy of the scan by the sensor while being moved at high speed by the robot has a corresponding high speed factor of approximately 0.30.

15. The apparatus of claim 1 wherein said means for moving the sensor at high speed comprises mechanism for moving the sensor rapidly along a preselected path including a plurality of segment scans at a speed of approximately 4" per second.

16. The apparatus of claim 1 wherein said means for moving the sensor at high speed comprises mechanism for moving the sensor rapidly along a preselected path including a plurality of segment scans at a speed of approximately 4" per second, means for providing a signal corresponding to the microwave energy levels scanned by the sensor as it is moved at said high speed along said path by said mechanism, means for providing a reference corresponding to acceptable levels of microwave energy leakage as sensed by the sensor as it is moved at said high speed along said path, and means for providing an indication whenever the level of microwave energy leakage sensed by the rapidly moving sensor at a position in said path exceeds the acceptable level thereat.

17. The apparatus of claim 1 wherein said means for moving the sensor at high speed comprises mechanism for moving the sensor rapidly along a preselected path including a plurality of segment scans at a speed of approximately 4" per second, means for providing a signal corresponding to the microwave energy levels scanned by the sensor as it is moved at said high speed along said path by said mechanism, means for providing a reference corresponding to acceptable levels of microwave energy leakage as sensed by the sensor as it is moved at said high speed along said path, means for providing an indication whenever the level of microwave energy leakage sensed by the rapidly moving sensor at a position in said path exceeds the acceptable level thereat, and means for redetermining the microwave energy leakage at said position while moving the sensor at a speed lower than said high speed to provide an increased accuracy determination of the microwave leakage thereat.

18. The apparatus of claim 1 wherein said means for moving the sensor comprises a robot.

19. The apparatus of claim 1 wherein said means for moving the sensor comprises means for accurately spacing the sensor from the oven while moving the sensor.

20. The apparatus of claim 1 wherein said moving means is caused to effect a repeated traverse of each location whereat said maximum leakage is sensed.

21. The apparatus of claim 1 wherein said moving means is caused to effect a repeated traverse of each location whereat said maximum leakage is sensed while causing the accuracy of the scan by the sensor to be increased during the repeated traverse.

22. The apparatus of claim 1 wherein said moving means is caused to effect a repeated traverse of each location whereat said maximum leakage is sensed while causing the accuracy of the scan by the sensor to be increased during the repeated traverse to a fine segment factor of approximately 0.98 wherein the factor is determined by the equation 1-maximum measurement error which could result from peak leakage along a specific scan being less than the true maximum were it to be located somewhere between scans as theoretically computed for different distances between such scans for potential leakage radiation patterns for a given microwave oven design.

23. The apparatus of claim 1 wherein said moving means is caused to effect a repeated traverse of each location whereat said maximum leakage is sensed while causing the accuracy of the scan by the sensor to be increased during the repeated traverse to a fine segment factor of approximately 0.98 wherein the factor is determined by the equation 1-maximum measurement error which could result from peak leakage along a specific scan being less than the true maximum were it to be located somewhere between scans as theoretically computed for different distances between such scans for potential leakage radiation patterns for a given microwave oven design, where the accuracy of the scan by the sensor while being moved at high speed by the robot has a corresponding coarse segment factor of between approximately 0.7 to 0.9.

24. The apparatus of claim 1 wherein said moving means is caused to effect a repeated traverse of each location whereat said maximum leakage is sensed while causing the accuracy of the scan by the sensor to be increased during the repeated traverse by a low speed factor of approximately 0.95 where the factor is determined by the equation 1-maximum measurable error as resulting from the instrumentation time response or filtering per theoretical computation for fast or slow instrumentation field probe speed past the potential narrowest beam leakage radiation pattern generated by a given design microwave oven including variation such as that generated by a microwave mode stirrer.

25. The apparatus of claim 1 wherein said second control means includes means for adjusting the control to compensate for an approximately 15% instrumentation error in determining the exceeding of said acceptable leakage.

26. The inspection method of determining the microwave leakage characteristic of a microwave oven having means for causing a time variable delivery of microwave energy to portions of the oven wherein such leakage may occur while said inspection method is being carried out in quality control of the manufacture of such ovens, comprising the steps of:

providing a microwave energy sensor;

providing mechanism for moving the sensor at a high speed of approximately 4" per second along a preselected path adjacent the oven to be inspected;

providing a signal corresponding to the microwave energy levels sensed by the sensor as it is moved along said path;

providing a reference corresponding to acceptable levels of microwave energy leakage as sensed by the sensor as it is moved at said high speed along said path;

providing a high leakage level indicating signal whenever the level of microwave energy leakage sensed by the rapidly moving sensor at a position in said path is at a high leakage level which exceeds the acceptable level thereat;

automatically controlling the sensor to reduce the sensor movement speed in response to said high leakage level signal;

redetermining the microwave energy leakage at said position while moving the sensor at a speed sufficiently lower than said high speed, to average out any time variations in the delivery of the microwave energy to said position, and while moving the sensor along said preselected path pattern which assures the accuracy of determination of the microwave energy leakage level thereat;

automatically controlling the movement of said sensor in accordance with the signal corresponding to the sensed microwave energy level to recommence high speed sensor movement when the sensed leakage level is acceptable; and

providing data relative to sensed high leakage level values and positions thereof along said path for use in effecting subsequent corrective actions as required.

27. The inspection method of determining the microwave leakage characteristics of claim 26 including the step of insulating the mechanism adjacent the sensor against pickup of ambient microwave energy for causing the sensed microwave energy level to accurately correspond to that along said path.

28. The method of determining excessive microwave radiation leakage of claim 26 wherein the sensor is caused to repeat traverse of the portion of the path at said position while causing the accuracy of the scan by the sensor to be increased during the repeated traverse to a fine segment factor of approximately 0.98 wherein the factor is determined by the equation 1-maximum measurement error which could result from peak leakage along a specific scan being less than the true maximum were it to be located somewhere between scans as theoretically computed for different distances between such scans for potential leakage radiation patterns for a given microwave oven design.

29. The inspection method of claim 26 further including the steps of providing a spacer in association with said sensor, and causing the spacer to be moved by said mechanism against the surface of the microwave oven along said path to maintain the sensor accurately spaced from the oven surface along said path.

30. The inspection method of claim 26 wherein said reference defines error limits at each position within which the sensed level is acceptable.

31. The inspection method of claim 26 wherein said oven includes a window having a transverse radiation blocking means and said path includes a portion extending along the edge of the window for detecting leakage at the edge of the blocking means and window.

32. The inspection method of claim 26 wherein the determination of the leakage level being sensed during high speed movement of the sensor is a coarse determination and the determination of the maximum leakage level being sensed during reduced speed movement of the sensor is a fine determination.

33. The inspection method of claim 26 wherein the determination of the leakage level being sensed during high speed movement of the sensor is a coarse determination, the determination of the leakage during an initial portion of the reduced speed operation is a coarse determination, and the determination of the maximum leakage level being sensed during reduced speed movement of the sensor is a fine determination.

34. The inspection method of claim 26 wherein the determination of the leakage level being sensed during high speed movement of the sensor is a coarse determination, the determination of the leakage during an initial portion of the reduced speed operation is a coarse determination, the determination of the maximum leakage level being sensed during reduced speed movement of the sensor is a fine determination, and the determination of the leakage at the end of said reduced speed operation is a coarse determination.

35. The inspection method of claim 26 wherein said step of moving the sensor comprises a step of causing a programmed movement of the sensor, and said sequence of speed reducing and maximum leakage determining steps is effected automatically during said movement.

36. The inspection method of claim 26 wherein the date providing step is effected upon completion of the movement along said path and data concerning each said maximum leakage determination is provided.