ENG4000Monitoring Capacitance Changes over

Various Materials and FluidsAysar Khalid, Hassan Chehaitli, Mohammad Aryanpour

Group 5

Course Director & Advisor: Prof. E. Ghafar-ZadehMentor: Giancarlo Ayala-Charca, Mourad Amara

Motivation

• Calibrating and understanding planar capacitors

• Detecting solid dry/wet material properties using planar capacitive sensors

• Current sensing technology is limited in accuracy

• Applications for pressure measurement, humdity sensing, impurity detection

(Lubepoint et. al, 2013)

Background • Capacitance sensors

detect a change in capacitance when something or someone approaches or touches the sensor.

• Current techniques (ESP) unable to work on low or high resistivity gases

• Different particles require different techniques

(Analog Devices et. al, 2006)

Particle Particle Size(microns)

Dust Mites 100 - 300

Starches 3 - 100

Asbestos 0.7 - 90Anthrax 1 - 5

Methodology● Planar capacitor is connected and produces Cx● Cx occurs when excitation signal (square wave) with f= 90.9 Hz● EVB then takes Cx and converts to digital signal using modulator/filter/etc.● Need to ensure minimal RF/EM interference on sensor

(Analog Devices et. al, 2006)

Progress Results To Date

# Sample Amount (3/10cc)

Capacitance (fF)

CAPDAC (hex / fF)

Offset Capacitance (fF)

1 Alcohol 1 unit 3984 42 / 8000.766

69.879

2 Alcohol 1 unit 3994 43 / 8000.898

-30.2331

3 Ginger Beer 1 unit 3894.134 43 / 8000.898

-9.472

4 Ginger Beer 1 unit 3623.641 43 / 8000.898

-9.102

5 Water 1 unit 3920.92 43 / 8000.898

-2.317

6 Water 1 unit 3900.99 43 / 8000.898

-2.338

Discussion From the last presentation• Sensor shielding and grounding• Developed and used aluminum die-cast

casing for shielding• Various fluids and better instrumentation• Calibration and stability

Conclusion ; Next Step • Make shielding more secure• Test more fluids/materials and samples for more tests• Connect sensor with LabView setup for data logging

• Noise from Laptop/measuring instrument

Acknowledgements Thanks to All the People and

Organizations who technically or financially supported your project