View
220
Download
0
Category
Preview:
Citation preview
7/31/2019 4 Level Measurement
1/26
4. Level Measurement
,
Lutfi Al-Sharif
7/31/2019 4 Level Measurement
2/26
pst c s.
Float S stems. Pressure Measuring devices.
. Ultrasonic systems.
Radar (microwave) methods.
. Other methods (laser, heated wire).
7/31/2019 4 Level Measurement
3/26
e o s o eve easuremen
7/31/2019 4 Level Measurement
4/26
Metal bar itched with markings.
.
Is only an approximate method.
Only suitable for shallow tanks.
devices.
Another simple device is the sight glass-tube.
7/31/2019 4 Level Measurement
5/26
7/31/2019 4 Level Measurement
6/26
Simple, cheap and widely used.
- .
Float and arm system with potentiometer
s use n cars or ue measurement. An th r t m i th fl t n t
gauge.
s cons s s o a ape wrappe on a s aconnected to a float.
7/31/2019 4 Level Measurement
7/26
As the fluid level changes, the float move
u and down and hence rotates the shaft. The rotation of the shaft is recorded and
. More complicated system but give better
accuracy.
7/31/2019 4 Level Measurement
8/26
By measuring the pressure at the bottom
of the vessel/tank the level can bededuced.
Open topped vessel.
Sealed vessel.
l r ni .
In the bubbler unit, the flow of gas isa us e un u es s ar o appear.
7/31/2019 4 Level Measurement
9/26
The level of the fluid can be arrived at by
dividin the ressure b the roduct ofand the density.
affect the accuracy of the result.
7/31/2019 4 Level Measurement
10/26
Hydrostatic Devices
7/31/2019 4 Level Measurement
11/26
The bubbler has an advantage over the
other two methods in that it does not sufferfrom the maintenance problem of leaks at
tappings.
7/31/2019 4 Level Measurement
12/26
By placing two parallel plates inside the
li uid and measurin the ca acitancebetween them, the level of the liquid can
.
The capacitance depends on the area ofthe plates, the distance between them and
the ermittivit of the li uid. The change in level changes the effective
capacitor.
7/31/2019 4 Level Measurement
13/26
Capacitive LevelSensing
7/31/2019 4 Level Measurement
14/26
Capacitive LevelSensing
7/31/2019 4 Level Measurement
15/26
If the liquid is non-conducting, then the
lates do not need to be insulated. However, where the liquid is conductive
. Liquids with high permittivity will provide
good sensitivity.
7/31/2019 4 Level Measurement
16/26
Ultrasonic devices are used to send and
receive the reflected ultrasonic si nal fromthe fluid level.
. The speed of sound in the fluid depends
on temperature.
compensate for the change inempera ure.
7/31/2019 4 Level Measurement
17/26
Frequency ranges from 40 kHz to 400
kHz. The speed of ultrasound also depends on
,dioxide concentration.
7/31/2019 4 Level Measurement
18/26
UltrasonicDevice
7/31/2019 4 Level Measurement
19/26
UltrasonicDevice
7/31/2019 4 Level Measurement
20/26
Still very expensive method.
(closed tanks, turbulence, and obstacles,
.
They rely on receiving a reflected signalwith a phase difference to the signal
Unaffected by temperature and pressurevar a ons as oppose o .
7/31/2019 4 Level Measurement
21/26
7/31/2019 4 Level Measurement
22/26
The tank filled with fluid is radiated at one
end and the out ut detected at the otherend.
rays depends on the amount of the fluid inthe tank.
-invasive.
7/31/2019 4 Level Measurement
23/26
7/31/2019 4 Level Measurement
24/26
Vibrating level sensor.
elements.
aser et o s.
7/31/2019 4 Level Measurement
25/26
7/31/2019 4 Level Measurement
26/26
Contact devices are less reliable that
contact-less devices. Methods that are less subject to variations
. .,microwave).
Recommended