Discerning between substances
A method and apparatus to detect the presence of a material at a sensing device and to determine whether the material is a first material having a first material property or a second material having a second material property.
1. A processing device implemented method comprising:
detecting a presence of a material at a sensing device;
wherein the sensing device comprises a first capacitive sensor configured to detect the presence of the material and an environmental effect on the sensing device, and a second capacitive sensor configured to detect the environmental effect on the sensing device; and
determining whether the material is a first material having a first material property or a second material having a second material property.
2. The method of claim 1 , wherein the first material comprises a powder and the second material comprises a gel.
3. The method of claim 1 , wherein the first and second materials comprise a liquid and wherein the first material property comprises a first dielectric constant of the liquid and the second material property comprises a second dielectric constant of the liquid.
4. The method of claim 1 , wherein detecting the presence of the material comprises measuring a capacitance value sensed by each of the first and second capacitive sensors.
5. The method of claim 4 , further comprising:
applying an offset to the first capacitive sensor such that the capacitance value measured by the first capacitive sensor is greater than the capacitance value measured by the second capacitive sensor.
6. The method of claim 5 , further comprising:
determining a difference between the capacitance values sensed by the first and second capacitive sensors.
7. The method of claim 6 , wherein determining whether the material is the first material having the first material property or the second material having the second material property comprises:
determining an increase in capacitance by comparing the difference between the capacitance values before the material is detected to the difference between the capacitance values after the material is detected.
8. The method of claim 7 , further comprising:
if the increase in capacitance is in approximately a range between a first threshold value and a second threshold value, determining that the material is the first material having the first material property; and
if the increase in capacitance is greater than approximately the second threshold value, determining that the material is the second material having the second material property.
9. The method of claim 5 , further comprising:
grounding the second capacitive sensor while the first capacitive sensor measures a first capacitance value and grounding the first capacitive sensor while the second capacitive sensor measures a second capacitance value.
10. The method of claim 5 , further comprising:
applying a shield signal to the second capacitive sensor while the first capacitive sensor measures a first capacitance value and applying the shield signal to the first capacitive sensor while the second capacitive sensor measures a second capacitance value.
11. An electronic system comprising:
a processing device configured to receive signals from a sensing device, the processing device to determine whether a material present at the sensing device is a first material having a first material property or a second material having a second material property;
a first capacitive sensor configured to detect the presence of the material and an environmental effect on the sensing device; and
a second capacitive sensor configured to detect the environmental effect on the sensing device.
12. The electronic system of claim 11 , wherein the first material comprises a powder and the second material comprises a gel.
13. The electronic system of claim 11 , wherein the first material comprises oil and the second material comprises water.
14. The electronic system of claim 11 , wherein the processing device comprises one or more capacitance sensors coupled to the sensing device, and wherein the one or more capacitance sensors are configured to measure a capacitance at the sensing device to detect the presence of the material at the sensing device.
15. The electronic system of claim 11 , wherein the first and second capacitive sensors are configured to measure a capacitance value.
16. The electronic system of claim 15 , wherein the processing device is configured to determine a difference between the capacitance values measured by the first and second capacitive sensors.
17. The electronic system of claim 16 , wherein the processing device is configured to determine an increase in capacitance by comparing the difference between the capacitance values before the material is detected to the difference between the capacitance values after the material is detected.
18. The electronic system of claim 17 , wherein determining whether the material is the first material having the first material property or the second material having the second material property comprises:
if the increase in capacitance is in approximately a range between a first threshold value and a second threshold value, determining that the material is the first material having the first material property; and
if the increase in capacitance is greater than approximately the second threshold value, determining that the material is the second material having the second material property.
19. The electronic system of claim 11 , wherein the sensing device comprises:
a capacitive sensor configured to detect the presence of the material; and
an environmental sensor.
20. An apparatus comprising:
means for detecting a presence of a material near a sensing device; and means for determining whether the material is a first material having a first material property or a second material having a second material property;
means for detecting the presence of the material and an environmental effect on the sensing device; and
means for detecting the environmental effect on the sensing device.
21. The apparatus of claim 20 , wherein the first material comprises a powder and the second material comprises a gel.
22. The apparatus of claim 20 , wherein the means for determining whether the material is the first material having the first material property or the second material having the second material comprises a non-contact means.
23. The apparatus of claim 20 , further comprising:
means for compensating for an environmental effect on the sensing device in detecting the presence of the material.