METHODS AND APPARATUSES TO TEST THE FUNCTIONALITY OF CAPACITIVE SENSORS

• US 20110050620A1
• Filed: 09/01/2009
• Published: 03/03/2011
• Est. Priority Date: 09/01/2009
• Status: Active Grant

• Current Assignee: Neodrón Limited (Atlantic IP Services Limited)
• Original Assignee: QRG Limited Level 1
• Inventors: Hristov, Luben
• Granted Patent: US 8,576,182 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844
• CPC Class Codes: G01R 31/64 Testing of capacitors
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

Some embodiments include apparatus and methods to test a device having a driving layer and a sensing layer. A test signal is applied to electrodes of the driving layer in a capacitive load state, with a capacitive load applied, and in an ambient state, without a capacitive load applied. Measured values are obtained at the sensing layer for each state. The measured values are compared with threshold values. A report is generated when a measured value violates a threshold. In one embodiment, the driving layer and the sensing layer form multiple capacitive electrodes within a touch sensor. The measured values are related to mutual capacitance values of the touch sensor.

Claims

1. A method, comprising:

supplying a test signal to a driving layer of a touch sensor while the touch sensor is in an ambient state;

measuring received signals at a sensing layer of the touch sensor, the sensing layer being electrically isolated from the driving layer, the measured received signals having measurement values corresponding to mutual capacitances between the driving layer and the sensing layer;

supplying the test signal to the driving layer while the touch sensor is in a capacitive load state, wherein the capacitive load state identifies a state of the touch sensor when a capacitive load is applied to at least a portion of the driving layer;

measuring the received signals at the sensing layer; and

comparing the measurement values to target threshold values to identify a fault point in a device.

2. The method of claim 1, wherein the test signal is an alternating current signal having a drive peak-to-peak voltage value, and wherein measuring the received signals at the sensing layer further comprises measuring sense peak-to-peak voltages of the received signals.

3. The method of claim 1, wherein the test signal is an alternating current signal having a drive peak-to-peak voltage value, and wherein measuring the received signals at the sensing layer further comprises measuring effective voltages of the received signals.

4. The method of claim 1, wherein the test signal is an alternating current signal having a drive peak-to-peak voltage value, and wherein measuring the received signals at the sensing layer further comprises measuring a maximum voltage of the received signals.

5. The method of claim 1, wherein the touch sensor is specified to operate within a minimum voltage and a maximum voltage over a range of touch events, and the ambient state and the capacitive load state are to simulate a plurality of touch events.

6. The method of claim 1, wherein the driving layer includes a plurality of conductive traces.

7. The method of claim 6, further comprising:

storing measured received signal data corresponding to the ambient state in a memory storage unit as ambient data; and

storing measured received signal data corresponding to the capacitive load state in the memory storage unit as capacitive load data, wherein the capacitive load state identifies a state of the touch sensor when the capacitive load is applied to the at least a portion of the driving layer.

8. The method of claim 7, wherein the plurality of conductive traces include a set of active electrodes and a set of interpolated electrodes, and wherein supplying the test signals to the driving layer in the capacitive load state comprises:

applying the capacitive load to the set of active electrodes corresponding to an active capacitive load state for the touch sensor;

supplying the test signal to the driving layer while the touch sensor is in the active capacitive load state;

measuring the received signals at the sensing layer while the touch sensor is in the active capacitive load state;

applying the capacitive load to the set of interpolated electrodes corresponding to an interpolated capacitive load state for the touch sensor;

supplying the test signal to the driving layer while the touch sensor is in the interpolated capacitive load state; and

measuring the received signals at the sensing layer while the touch sensor is in the interpolated capacitive load state.

9. The method of claim 6, wherein supplying the test signal to the driving layer further comprises supplying the test signal to one of the plurality of conductive traces of the driving layer, and wherein the sensing layer includes a plurality of conductive traces, and measuring the received signals at the sensing layer further comprises measuring the received signals at each of the conductive traces while supplying the test signal to the one of the plurality of conductive traces of the driving layer.

10. The method of claim 9, wherein the method is repeated for each of the plurality of conductive traces of the driving layer.

11. The method of claim 1, further comprising calculating at least one value corresponding to a mutual capacitance based on the measured received signals, and comparing the at least one value to a designated threshold to identify a fault condition in the touch sensor.

12. A test system apparatus, comprising:

an electrical measurement unit to;

apply a test signal to a conductive trace of a plurality of conductive traces formed in a driving layer of a device; and

measure at least one electrical characteristic of a sensing layer of the device;

apply a capacitive load to at least a portion of the plurality of conductive traces formed in the driving layer; and

measure the at least one electrical characteristic of the sensing layer with the capacitive load applied to the at least a portion of the plurality of conductive traces; and

a processing unit to;

compare a measurement of the at least one electrical characteristic to threshold values; and

generate a failure report when the measurement violates a first threshold value of the threshold values.

13. The test system apparatus of claim 12, further comprising:

a base unit to accept the device; and

a conductive cover unit to apply the capacitive load to the at least a portion of the plurality of conductive traces.

14. The test system apparatus of claim 13, wherein the conductive cover includes a first portion of contacts for connecting the capacitive load to the at least a portion of the plurality of conductive traces formed in the driving layer.

15. The test system apparatus of claim 13, further comprising:

a memory storage unit to store the threshold values.

16. The test system apparatus of claim 15, wherein the threshold values include a first threshold value corresponding to an ambient state of the device, and a second threshold value corresponding to a capacitive load state of the device.

17. The test system apparatus of claim 16, wherein the driving layer includes a set of active electrodes and a set of interpolated electrodes, and wherein the processing unit is further to:

compare the measurement of the at least one electrical characteristic taken when the capacitive load is applied to the active electrodes to the first threshold value, and

compare the measurement of the electrical characteristic taken when the capacitive load is applied to the interpolated electrodes to the second threshold value.

18. The test system apparatus of claim 13, further comprising:

a memory storage unit to store the measurement of the at least one electrical characteristic.

19. The test system apparatus of claim 18, further comprising:

a test application unit to store computer-readable instructions to;

select a first test signal to test the device; and

select a capacitive load to test the device.

20. A computer-readable medium comprising instructions, which when implemented by one or more machines, cause the one or more machines to:

measure an ambient electrical characteristic of a dual layer sensor while in an ambient state, the dual layer sensor having a driving layer and a sensing layer;

measure a capacitive load electrical characteristic of the dual layer sensor while a capacitive load is applied to the driving layer;

compare the ambient electrical characteristic and the capacitive load electrical characteristic to corresponding threshold values;

report a failure when the measured ambient electrical characteristics violates an ambient threshold value; and

report a failure when the measured capacitive load electrical characteristic violates a capacitive load threshold value.

21. The computer-readable medium of claim 20, wherein the device is a touch sensor, and wherein the instructions are further to supply a test signal to a conductive trace of the driving layer and to measure received signals at each of a plurality of conductive traces in the sensing layer.

22. A test apparatus, comprising:

a base plate having a position frame portion to receive a dual layer device; and

a conductive top layer to apply a conductive load to the dual layer device for test, the conductive top layer having a plurality of elongated members configured to couple with conductive traces on a driving layer of the dual layer device.

23. The test apparatus of claim 22, wherein the test apparatus includes an input port to receive instructions for testing the dual layer device, wherein the testing is to measure an electrical characteristic of the dual layer device, and the electrical characteristic related to a mutual capacitance between the driving layer and the sensing layer of the dual layer device.

24. The test apparatus of claim 22, wherein the apparatus is part of a testing system, the testing system comprising:

a signal source unit to supply the test signal to the test apparatus; and

an electrical measurement unit to measure the electrical characteristic; and

a load generator to supply at least one capacitive load to the dual layer device.

25. The test apparatus of claim 22, wherein the conductive top layer comprises a conductive foam.