Sensors and Signal Conditioning EEE-4021
Name: Dibyanshu Mohanty
Reg no. 20BEE0401
EXPERIMENT-4
AIM:
To measure tank level using capacitance level probe
THEORY:
Capacitive level sensor is used for wide variety of solid, aqueous and
organic liquids and slurries. This technique is frequently referred as radio
frequency in digital applied capacitance circuit. The sensor can be
designed to sense material with dielectric constant as low as1.1 and as
high. Capacitive level sensor are electronic device phase modulator and
the use of change in frequency makes for the sensor suitable for
applications in which the dielectric constants are similar.
WORKING PRINCIPLE:
The principle of capacitive level measurement is based on change of
capacitance. An insulated electrode acts as one plate of capacitor and the
tank wall (or reference electrode in a non metallic vessel) acts as the
other plate. The capacitance depends on the fluid level. An empty tank has
a lower capacitance while a filled tank has a higher capacitance. A simple
capacitor consists of two electrode plate separated by a small thickness
of an insulator such as solid, liquid, gas, or vacuum. This insulator is also
called as dielectric. Value of C depends on dielectric used, area of the
plate and also distance between the plates.
C = E (K A/d)
Where:
C = capacitance in Pico farads (pF)
E = a constant known as the absolute permittivity of free space
K = relative dielectric constant of the insulating material
A = effective area of the conductors
d = distance between the conductors
This change in capacitance can be measured using AC bridge.
PROCEDURE:
1. Study the given diagram completely.
2. Select the height of the tank in centimeters.
3. The value of radius of outer cylinder/pipe for pipe in pipe type probe r2
is fixed 2.5cm.
4. Select the value of radius of inner cylinder/pipe for pipe in pipe type
probe r1 in centimeters.
5. Span value will get displayed. Span is 90% of the height of the tank.
6. Select the service for which capacitance probe is to be used.
7. Click on 'Configure System'. It will ask for confirmation.
8. After confirming, select the fluid level from drop down menu for
selected service.
9. Enter the calculated user output capacitance in µF. Using formula
calculate the value of the output capacitance for the corresponding level
and enter the answer in the box provided (up to 2 decimals with rounding
off). Submit the answer using submit button.
10. Study the graphs for RTD performance with different reference
resistance values and different materials if your calculation is correct it
will be displayed on the screen. Minimum three calculations are necessary
to plot the graph. Click on level vs. capacitance graph and level vs. current
graph and study them.
FIRST OBS.
Observation:
Height of tank: 2500cm
Outer radius: 2.5cm
Inner radius: 1.2cm
Span value: 2245
Service: Water
Observation Table:
Level (cm) Cout
225 1.56
450 2.82
672 4.21
900 5.56
1125 6.9
Observation:
Height of tank: 2500cm
Outer radius: 2.5cm
Inner radius: 1.2cm
Span value: 2245
Service: Water
Observation Table:
Level (cm) Cout
225 0.35
450 0.66
672 0.98
900 1.3
1125 1.5741
Output Graphs
SECOND OBS.
Observation:
Height of tank: 3500cm
Outer radius: 2.5cm
Inner radius: 1.6cm
Span value: 3145
Service: Skimmed Milk powder
Observation Table:
Level (cm) Cout
315 0.42
630 0.49
941 0.52
1260 0.56
1575 0.61
Observation:
Height of tank: 3500cm
Outer radius: 2.5cm
Inner radius: 2.1cm
Span value: 3145
Service: Skimmed milk powder
Observation Table:
Level (cm) Cout
315 1.1
630 1.3
941 1.4
1260 1.5
1575 1.7
Output Graphs:
INERENCE:
We have successfully measured the level of the tank using capacitive type
level probe. Here we observe that with an increase in the value of inner
radius, the value of capacitance also increases.
LEAST SQUARE ANALYSIS:
