Capacitive Sensors For Flow Application

Surname 1

Student’s Name

Professor’s Name

Course

Date

Capacitive Sensors for Flow Application

Capacitive sensors due to their relatively low cost of production and a wide range of

applications have been used for several years. One of the applications of capacitive sensors is the

detection and measurement of fluid flow, based on capacitive coupling. They work on the

principle that they can measure and distinguish the conductivity of the fluid that has a different

dielectric constant from the electrodes used. Furthermore, it employs the theory of pressure drop

due to the reduction in diameter to measure the flow of fluids in pipes associated with the

geometry of electrodes and the direction of fluid flow (Mohamad, Marwah and Rahim, 1). The

fluid flowing in the pipe, in this case, acts as the dielectric whereby the two opposite electrodes

produces different capacitance. Permittivity in flow measurement will then become 𝜀

𝑜

and 𝜀

𝑟

determined as the fluid dielectric property across the sensing volume in the measuring boundary

of the sensor (Mohamad et al., 1). The measurement of the capacitance is then obtained as:

𝐶 =

𝜀

𝑜

𝜀

𝑟

𝐴

𝑑

𝑝

In this case:

C= Capacitance in Farads

𝜀

𝑜

= The free space permittivity

𝜀

𝑟

= Dielectric permittivity

A= plate area

𝑑

𝑝

= plate distance

Capacitive sensing in fluid flow is a non-destructive type of measurement. This is

because the flow of the fluid is measured without causing any kind of destruction to the flow

canal (Al Shaqsi, 1). The capacitive sensor has one pair of electrodes that are semi-cylindrical in

shape whereby the materials are made from adhesive foils of soft copper metal. The electrodes

are mounted on opposite sides of the pipe thereby allowing non-destructive measurement of the

fluid flow inside the tube. The two electrodes are connected to an external circuit that generates

an electromagnetic field in the pipe cross section, and therefore, the flow is measured. When no

flow is detected on the tube, the capacitance generated will be less than the one in the conductive

fluid. On the contrary, when the fluid flows, through the electromagnetic field the semi-

cylindrical electrode will measure a capacitance value (Al Shaqsi, 17). One of the electrodes is

the negative terminal while the other is positive, but are made such that they are equal in size and

area. The surface of the pipe is insulated with a non-conductive layer of dielectric material like

wood or paper so that charge loss and outside, charge-interaction is prevented. This ensures the

eddy flow is not disturbed.

Surname 2

Fig1. The capacitor sensing for fluid measurement illustration (Al Shaqsi, 18).

Since flow meters will cause the fluid to change its displacement so as to determine the

flow, the capacitive sensing does not require a change in the movement of the fluid to take in

measurements. The capacitance of the capacitive sensor will vary with the fluid flow dielectric

property between the two semi-cylindrical electrodes (Mohamad et al., 1). The flow rate is

determined through the measurement of the difference in capacitance between the conductive

fluid and the semi-cylindrical electrode, therefore; it is a good sensor, unlike other flow meters.

A typical manufacturer of capacitive sensors for flow measurements is MTI instruments.

The model number of the capacitive sensor is the AS-9000/1 system. The instrument has an

accuracy of 0.02% FSR Root Mean Squared with a minimum range of 25μF for every 0.001

inches. It measures the fluid flow with a precision of 25mm, pipe diameter thickness. The

relevant specifications include:

1. Offset/gain control function

2. Integral summing amplifier for the pipe thickness output

3. Bar graph display

Surname 3

Works Cited

Al Shaqsi, Harith Hilal. "Non-Destructive Flow Measurement." Engineering project. 2010.

Digital print.

Mohamad, Evans Johana, Faizan Olga Marwah and Abdul Ruzari Rahim. "Electronic Design for

Portable Electrical Capacitance Sensor: A Multiphase Flow Measurement." Institute of

Electrical and Electronics Engineers (2011): 1-8. Digital print.

Place new order. It's free, fast and safe

Paper type

Deadline

Page count

550 words

Total price: $ 15.00

Our customers say

Jeff Curtis

USA, Student

"I'm fully satisfied with the essay I've just received. When I read it, I felt like it was exactly what I wanted to say, but couldn’t find the necessary words. Thank you!"

Ian McGregor

UK, Student

"I don’t know what I would do without your assistance! With your help, I met my deadline just in time and the work was very professional. I will be back in several days with another assignment!"

Shannon Williams

Canada, Student

"It was the perfect experience! I enjoyed working with my writer, he delivered my work on time and followed all the guidelines about the referencing and contents."